THE TESLA GLOW DISCHARGE IN ORGANIC COMPOUNDS
PART I
MOLECULAR EMISSION SPECTRA
AND CHEMICAL REACTIONS
PART I I
APPLICATION TO GAS CHROMATOGRAPHY
DETECTION

By
Richard E* F oulson

A THESIS

Subm itted t o t h e S ch o o l f o r Advanced Graduate S tu d ie s
o f M ichigan S t a te U n iv e r s ity o f A g r ic u ltu r e and
A pplied S c ie n c e i n ' p a r t i a l f u lf i llm e n t o f
th e requirem ents f o r th e d egree of
DOCTOR OF PHILOSOPHY
Department o f Chemistry

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ACKNOWLEDGMENTS
I w ish t o exp ress my g r a titu d e fo r
th e i n t e r e s t and generous guidance o f
P r o fe s so r James C« S tern b erg throughout
t h i s in v e s tig a tio n .,
To A ly c e , my w if e , who p a t ie n t ly
gave encouragement and s e l f s a c r i f i c e
I o f f e r my deep and e v e r la s t in g a p p reci­
a t io n o The p rep aration o f th e drawings
i s but a s in g le example o f her in v a lu a b le
a s s is ta n c e „
The f i n a n c ia l aid re c e iv e d from a
N a tio n a l I n s t it u t e s o f H ealth grant in th e
f i n a l s ta g e s o f t h i s work was of much
a s s is t a n c e <>

THE TESLA. GLOW DISCHARGE IN ORGANIC COMPOUNDS
PART I
MOLECULAR EMISSION SPECTRA
AND CHEMICAL REACTIONS
PART I I
APPLICATION TO GAS CHROMATOGRAPHY
DETECTION
By
Richard Eo P oulson

AN ABSTRACT

Subm itted t o th e S ch ool f o r Advanced Graduate S tu d ie s
o f M ichigan S ta te U n iv e r s ity o f A g ricu ltu r e and
A pplied S c ien ce in p a r t ia l f u lf illm e n t o f
th e requirem ents fo r th e d egree of
DOCTOR OF PHILOSOPHY
Department o f Chemistry
Year 1959

ABSTRACT
The T e sla c o il-e x c ite d * e le c tr o d e l e s s , glow d isch a rg e in gases a t
reduced p re ssu r e has been stu d ied from an approach design ed t o determ ine
how r e l a t i v e l y sim ple ex p erim en tal tech n iq u es can be used t o o b ta in in f o r ­
m ation con cern in g e le c tr o n -im p a c t-e x c ite d e le c t r o n ic s t a t e s o f atoms,
m olecu les and io n s , and t h e ir p art in chem ical r e a c tio n s * R e su lts o f t h i s
in v e s t ig a t io n were a p p lied to develop two e a s ily —co n stru cted , in e x p e n siv e ,
io n iz a tio n - ty p e d e te c to r s fo r gas chromatography*
A b r i e f summary o f b a s ic energy tr a n s fe r p r o c e sse s in th e glow d is ­
charge i s p resen ted .,

The f i e l d o f em issio n sp e c tr a e x c ite d in th e glow

d isch a rg e i s rev iew ed *
Employing a reco rd in g p h o t o e le c t r ic spectrophotom eter f o r rapid
scan nin g o f v i s i b l e and u l t r a v i o l e t sp e c tr a , and an e x c it a t io n tech n iq u e
s im ila r t o th a t developed by H» S ch u le r , but w ith a T esla c o i l e x c it e r
and flo w in g c a r r ie r gas t o e x c it e organic vap ors, glowed i s charge em issio n
s p e c tr a were s tu d ie d »
In an argon d isc h a r g e , stron g red (a rc) spectrum l in e s of argon were
observed to g e th e r w ith v e r y weak b lu e (spark) spectrum lin e s *

A lip h a tic

a lc o h o ls , a lk a n e s, ben zen e, and oxygen quenched th e red spectrum s e l e c t i v e l y ,
le a v in g th e spark spectrum and a v ery few arc s p e c tr a l l i n e s undim inished
in in te n s ity *

Water and n itr o g e n did not quench th e spectrum s e l e c t i v e l y .

The phenomenon i s in te r p r e te d in terms o f b a s ic p r o c e sse s known t o occur
in a gaseous d isch arge*

Glow d isch a rg e decoup o s i t i o n p a tte r n s in terms o f r e l a t i v e i n t e n s i ­
t i e s o f em issio n by d iatom ic and atom ic fragm ents were recorded f o r many
fla w in g organ ic vapors (w ith ou t th e use o f a c a r r ie r g a s ) .
a lc o h o ls , a c e to n e , alk an es and a lk y l h a lid e s were su rveyed .

A lip h a tic
The r e l a t i v e

i n t e n s i t i e s o f th e v a rio u s e m itte r s in th e d isch arge were observed t o
change c o n sid er a b ly as th e p ressu re (and th e r e fo r e e le c tr o n energy range)
was a lte r e d o

P o s s ib le in te r p r e ta tio n s o f gross fe a tu r e s o f th e decompo­

s i t i o n p a tte r n s were su ggested in terms o f mechanisms which seem most
p ro b a b le,b a sed on what i s known b a s ic a lly o f e le c tr o n impact e x c it a t io n
and energy tr a n s f e r in a gaseous d isc h a r g e .
U sing th e T esla c o i l as an e x c ite r , two s e n s it iv e ,in e x p e n s iv e
io n iz a tio n - ty p e d e te c to r s fo r gas chromatography have been d evelop ed ,
A p h otom etric form and an e l e c t r i c a l form, each capable o f wide a p p lic a tio n
in p r e p a r a tiv e chrom atographic work and fo r le c t u r e dem onstration purposes
were s tu d ie d .

The p hotom etric form o f th e d e te c to r employs a photo­

conducting c e l l t o measure th e l i g h t i n t e n s it y change in th e d isch a rg e
w ith th e p assage o f th e chromatographic component.

The e l e c t r i c a l form

o f th e d e te c to r i s based on th e p a r t ia l r e c t i f i c a t i o n o f a h ig h frequency
cu rrent which ta k es p la c e a t two se n sin g e le c tr o d e s (prob es) p laced
a sy m m etrically in th e glow d isc h a r g e .

The current flow through an e x te r n a l

r e s is t a n c e con n ectin g th e e le c tr o d e s i s m onitored, and changes o f th e order
o f microamperes occur when components p ass through th e d e t e c to r .
Both d e te c to r s were estim ated to have a p resen t lim it o f d e t e c t a b i l i t y
f o r methane ( s ig n a ls n o is e = 2 s i ) of approxim ately 10

v

m oles.

The d e te c to r s w i l l sen se l i g h t and in e r t gases as w e ll as organ ic
vapors o
The most s e n s i t i v e forms o f th e d e te c to r s d ev ised employed argon as
a c a r r ie r g a s, but any c a r r ie r gas (in c lu d in g a ir ) may be used depending
on th e a p p lic a t io n .

With argon c a r r ie r gas i t was found d e s ir a b le to

b le e d oxygen v e r y s lo w ly in to th e d e te c to r to r e a c t w ith C2 and s im ila r
r a d ic a ls t o p rev en t polymer d e p o s itio n in th e d e te c to r and subsequent
t a i l i n g o f component b an d s.
An in te r p r e ta t io n o f th e resp onse o f th e s e d e te c to r s and oth er
io n iz a tio n - ty p e d e te c to r s in terms o f b a s ic p ro c e sse s in th e d isch a rg e i s
o u t lin e d .
S u g g e stio n s and p relim in a ry ob serv a tio n s r e la t iv e t o q u a lit a t iv e
a n a ly s is o f components o f gas chromatography by t h e ir s p e c tr o s c o p ic a lly
observed crack in g p a tte r n s are p r e se n te d .

TABLE OF CONTENTS
Page
INTRQDUCTX O N . o . o o o . . . o . o <>, o, • . 0 , 9 . o . o . o o o . , , . , . o, . . 0 0 , . 0 , . . o *
A»
B.
C.
Do

1

G eneral Course o f th e W o r k . o o o o , . . . , , . . . , . . . . . 1
.....................
3
P r o p e r tie s o f th e Glow D isc h a r g e
E le c tr o n Impact E x c ita tio n in th e Glow D i s c h a r g e ,,......................
U
Summary o f P r o c e sse s Taking P la c e in th e Glow D i s c h a r g e . . . . . .
5
PART I
MOLECULAR EMISSION SPECTRA
AND CHEMICAL REACTIONS

A. A Review o f Glow D isch arge Em ission S p ectra and R elated F i e l d s •«

12

1 . Em ission S p ectra o f P olyatom ic M olecules and I o n s
a . Ear l y W
Tork ooooo. eoooceoo, . 00 , . 000000000 . 0 . 0000000 . . o
b o The Technique and Work of H. S c h u l e r . . . . . . . . . . . . . . . .
( 1) The Bas l c Technique. . . . . . . . . . . . . . . o . . . o . . . , , o .
( 2) Mechanism o f E x c ita tio n in th e Glow D ischarge
(3 ) R efinem ents o f th e Technique Which Aid in '
I d e n t if y in g S p e c tr a l Emi t t e r s . . . . . . . . . . . . . . . .
(U) New S p ectra Observed by th e S ch u ler Tech-*
ni queaoao» 0 . o o . . a . . o o » . . o « 00 . o . « o . o . . « o . , o « . o
( 5) L im ita tio n s o f th e Techni que. . . . . . . . . . . . . . . . .
c . R e su lts from oth er Techniques of Glow D ischarge
E x c ita tio n o f M olecular E m ission S p e c t r a . ...........
2 . S tu d ie s o f R eaction Mechanisms in th e Glow D i s c h a r g e . . . . . .
a o GenOra l e e o 0 OO,oa0 OB0 e » . . o o e o # . . . » 0 e ». ao 9 O. » e . . a e . . a »
b . Chemical A n a ly sis o f Products . . . . . . . . . . . . . . . . . . . . . . .
.............
c . S p e c tr o sc o p ic Em ission S tu d ie s
3 . Other Sources o f E lectro n Impact E x c i t a t i o n . . . . . . . . . . . . . . .
a . I o n iz m g Rad i a t i o n o o . . . . . . . . . . . . . . . . . . . . . . . . .
b . The Mass S p ectrograp h
.............

12
12
13
13
16

B . E m ission S p e ctra in a Flow System w ith a C arrier Gas. . . . . . . . . . . .
1 0 E xp erim en tal. . 0 . 0 . 0 . 00 , . . a o 0 o o . . o o . o » . o . . . e . a o . o . . » . . . . o o .
a . G eneral D e s c r ip tio n o f Experim ental Approach. . . . . . . .
b 0 ReagentS oo. aooooeo 0 . o . 0 . . o o « o o 0 e e o o o . o e o o . . . a . , o . , o .
( l ) ArgOn . 0 . 00000000 . o. . . . o o . . . . . . o o , o. oo. . «o. « a.
( 2) Hel i um. . . . . 0000 . 0000 . 00 . . 000 . 0 . 0 . 00 . 00000 . 0.0
( 3) Organic S a m p l e s o . o o . o o o . o . o o . o . o . . . . . . . . . . . . .
CO Apparatus 000 . 0 , 00 o . o . a 0 oO0 . o . o « o . o . o o o » . . . e o , » . . o « . o
( 1 ) D isch arge System . 0000 . ooao poo. ao. o o. oo. a. o. oo
(2 ) O ptics and S p e c t r o p h o t o m e t e r . . . . . . o . . . . . . . . . .
(3 ) The E x c ite r 0 O.O0 OOOO0 OO0 O00 O00 OO0 . OOO. . . . 0 O.O
continued
v ii

19
20
22

23
25
25
26
27
29
29
30
31
31
31
32
32
33
33
3^43^-4
37
38

TABLE OF CONTENTS » Continued
Page
d * Experim ental Pr o c e d u r e o ®. ®. . ®. . . . . . . . . . . . .................... . . 1*0
( 1) W avelength Measurement
............................................UO
( 2 } O perating the. D isch arge Systenj. . . . . . . . . . ®. . . . UO
2 o R e su lts and D is c u ss io n oooo®. . . ®. . ®. . . ®®®. . . . . . . . . . . . . . " .......... k3
a 0 Quenching o f th e Argon S pectru m ................................ . . . . . b3
b . The B lu e Spectrum o f Argon
........................... U5
Co C o r r e la tio n o f th e Observed B lue Spectrum w ith th e
B lu e Spectrum o f Argon
.............
U6
d . Helium C arrier Gas
..........
1+6
eo P olyatom ic M olecular S p e c tr a
...........
h9
f o I n te r p r e ta tio n o f S e le c t i v e Quenching o f th e Argon
Red Spectrum
...........
b9
3* S u g g e stio n s f o r Further Work w ith Argon C arrier G a s . . . . . . . 5U
a. E f f e c t o f th e Nature o f E x c ita tio n on E le c t r o n '
E n ergies In th e D isch a rg e ...............
5U
bo R e la tiv e E f f e c tiv e n e s s of Various Quenchers.................. 55
Co E m ission S p ectra in a Flow System w ith o u t a C arrier Gas..................

57

1 o E xp erim en tal
...............
57
ao G e n e r a l o o o o o o . a a o o o o o e . e o o . . . . . . . . . . . . . . . . . . . . . . . . . . 57
b o M o d ifica tio n s of P reviou s Apparatus. • • • • • » * . . • • .......... 57
c . Procedure During a Run®
......................
60.
2 o R e su lts and D is cuss ion*
...........
61
a . K e t o n e s . . . . . . . o o o o o . o o o o o . . . . . . 61
b . A lc o h o ls , Alkanes and A lk y l H a lid e s
............ 63
c . I n te r p r e ta tio n o f D ecom position P a t t e r n s
67
(1^ G e n e r a l o . o o . o e o o o o o » o . . * . . » . . . . . . . . . . . . . . . . . . 67
( 2) A lc o h o ls f A lkanes, A ceton e
..................
6?
................................................ 72
(3 ) A lk y l H a l i d e s . . . . .
3 . Summary o f Work w ith ou t a C arrier Gas..........................
7i+
U. S u g g e stio n s f o r Further Work w ith o u t a C arrier G a s . . . . . . . . 75
PART I I
APPLICATION TO GAS CHROMATOGRAPHY
DETECTION
A. I n tr o d u c tio n , o o . . . . . . . . o o . . . . . . . . . . . . . 00 . * o . . . . . . . . . . . . . . . . . . . . . .

77

B . B r ie f Summary o f D e te c to r s f o r Gas Chromatography. . . . . . . . . . . . . . .

79

Co P r o p e r tie s o f th e T esla E x cited Glow D isch arge Amenable t o
Measurement o o o o . o o . . . . . . . . . . . ® . ® . ® . ® . . . . . . . . . . . . . . . . . . . . . . . . . . . .

31+

continued
v iii

TABLE OF CONTENTS - Continued
Page
D. E

x p

e r i m

e n

t a l .

........... . . . . . . . . . ............... . . .

86

1 o R eagents . . . . . . . . . . . . . . . . . .
................
* . • . . .......... 86
a. Compressed G ases.................. . . . . ................ . . . . . . . ............. . . 86
bo A ir o . o. . o. o * « . .............
87
co N atu ral Gas......................
87
..........
87
d « Organic Liquid Samples
2 o A pparatus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
87
a. G eneral D e s i g n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
87
b o D e te c to r C o n s t r u c t i o n .................
89
(1 ) M echanical D e t a il o f ^Sensing E lem en ts. . . . . . . .
89
( 2 ) E x c ite r T u b e.
.............
92
(3 ) E l e c t r ic a l C i r c u i t s . . . . . . ....................
9k
( a) G en eral
9k
...............
9U
(b ) E l e c t r i c a l D e t e c t o r
( c ) Photom etric D e t e c t o r . . . . . . . . . . . . . . . . . .
97
c . The Flow S y s t e m
.............. ................................... *.
97
(1 ) G e n e r a l................. . . .......................... . . . . . ................... 97
( 2) O peration w ith ou t a Chromatographic C olum n... 99
100
(3 ) Oxygen S caven ger. . . . . . .............
3 . Experim ental P roced u re
..........................
100
a . G eneral D e t a i l s ..................
100
(1 ) Sampling T echniques
100
(2} P ressu re and Flow R
a
t
e
.
102
(3 ) Chromatograms
.............
103
b . Procedure Using th e Photom etric D e t e c t o r . . . . . .................103
c . Procedure Using th e E le c t r i c a l D e t e c t o r . ...........
103
E . R e s u lts and D is c u s s io n ...............

105

1 . P hotom etric O b s e r v a t io n s ...
...............
105
a . G en eral...............................
105
b . O v e r -a ll L igh t I n t e n s i t y . ...............
106
c . Quenching o f C arrier Gas S p e c t r u m . . . . . . . . . . . . . . . . . . . 108
d . S e l e c t i v e O bservation o f Em ission by th e S a m p l e ..... 108
e . Q u a lita tiv e A n a ly sis o f Chromatographic Components.-. 109
f . S t a b i l i t y o f th e D is c h a r g e ..
...............112
g . Summary.
.................
113
2 . The E l e c t r i c a l D e te c to r -R e s u lts and D i s c u s s i o n . . . . . . . . . . . . 113
a. S e le c t io n o f System s t o Study and D isch arge
O perating C o n d itio n s
...............
113
(1 ) C a rrier G ases.............................
113
(2 ) Apparent E l e c t r i c a l C h a r a c te r is tic s o f th e
D e te c to r D isc h a r g e
.................
I ll;
continued
ix

TABLE OF CONTENTS - Continued
Page
b„

c.

d.
e.
f.

(3 ) E f f e c t o f P ressu re on D etecto r P r o p e r t i e s . . . . 117
Response o f D ector U sing A ir C
a r r i e r 123
(1 ) L igh t G ases.................
123
(2 ) R e p r o d u c i b i l i t y . . . . . ......................................................126
(3 ) Higher Hydrocarbons
........ ............................... 127
(h ) Water Vapor
...................................
127
Response o f D e te c to r U sing Argon Ca r r i e r . . . . . . . . . . . . 128
(1 ) Oxygen S caven ger
...............
128
(2 ) Methane
.............
128
(3 ) Higher Hydrocarbons
...............
130
133
(U) Organic. L iq u id s .................
(5 ) A i r . .
................ . ............... ....................................... 133
...........
133
( 6 ) Sample Chromatograms
I n flu e n c e o f D e te c to r Geometry on 'S e n s it iv ity .'
; • . 138
..............................................
139
S u m m a r y ....
I n te r p r e ta tio n o f E l e c t r ic a l D e te c to r R e s p o n s e . .. .. . lhO

F . Comparison o f th e Photom etric and E le c t r ic a l T esla D is c h a r g e ’
D etecto rs
.............
1.
2.
3.
k°
5.

S e n s itiv ity .
....................
R ete n tio n Volume
...........
L in e a r ity o f R esp on se.................
C arrier G a s e s . . . . . ..........................
S e le c tiv ity .
......................................

G. S u g g e stio n s f o r A p p lic a tio n s and

F urther Work

±hh
lhh
U4J4
Ih5
Ih5
11*6

...............

1.
2o
3.
h.

L ecture D em onstration and P r ep a ra tiv e W ork ...............................
Humidity Measurement........................
Vapor P ressu re and M olecular Weight D e t e r m i n a t i o n . . . . . . . . .
................
Q u a lita t iv e A n a ly s is
a . General . . . . . . . . . ...............
b . Rapid Scanning S pectroph otom etry. ................................
c . T e sla D is charge Cracking ...................................
5 . High M olecular W eight Compounds............
...................

Ih 6
IJ4.6
l l *8
l i ;8
1 U9
Ih9
150
150
151

H. O v e r -a ll Summary o f E l e c t r i c a l D ete c to r s f o r Gas Chromatography. 151
LITERATURE CITED..

.............................

156

APPENDIX (DATA FOR F I GURE S ) . . . . . . ..............................................................

x

160

LIST OF TABLES
TABLE
I
II
III
IV

Page
R e s u lts o f Quenching o f Argon Glow D isch arge Spectrum w ith
V arious S u b sta n c e s•
. . . . . . ...........

UU

C o r r e la tio n o f Observed Spectrum in Quenched Argon w ith
B lu e Argon S p e c t r u m * . o . . . . . . . . . . . . . . . . . . . . ............... . . . . . . ..........

U7

K etones Observed i n Glow Di s c h a r g e . . . . . . ....................

62

D ecom position P a tte r n s o f A lip h a tic A lc o h o ls, Alkanes and
A cetone in th e Glow Di s c h a r g e . . . . . . . . . . . . . . . . . . . . . . . ................

65

V

D ecom position P a tte r n s o f A lk y l H alid es in th e Glow
c h a r g e o . o o . o o . . . . . . . . . . . . . . 66

VI

Response o f Photom etric D etecto r t o Various Sample G a s e s . # . . 110

VII
V III

E stim ated S ig n a l-t o -N o is e R atios f o r A ir , Argon and Helium
C a r rie rs—Response to 0 .0 1 Ml. Methane I n j e c t i o n . .

115

E f f e c t o f S c a le M u ltip lie r R esista n c e on Current i n th e
E l e c t r i c a l D e te c to r f o r Argon and Helium a t Various
P ressu res
...............

118

IX

Response in A ir C arrier t o 20 Ml. I n j e c t io n s o f 1 .1 Volume
P e rcen t S o lu tio n s in A ir fo r Various Sample G ases..........................125

X

R e la tiv e Response t o 50 Ml. I n je c tio n s o f 0 .6 Volume
P e rcen t S o lu tio n s o f Hydrocarbons in Argons Ar (* 0 2) C arrier 132

XI
X II
X III

Response t o 50 M l. I n j e c t io n s o f Organic Vapor S o lu tio n s in
Argonj Ar (* 0 2) C a r r ie r
......................
D e te c to r Current v s . A pplied V oltages A ir C a r r ie r

13h

............160

D e te c to r Current v s . P r essu re fo r N2, A ir , Ar and He
C arrier G ases
..................

161

XIV

Response t o 20 Ml. I n j e c t io n s o f H2, CH4 , and He S o lu tio n s
in A ir , A ir C a r r ie r , as a F unction o f P r e s s u r e . . . . . . . . . . . . . . 162

XV

R esponse t o 20 Ml. I n j e c t io n s o f He, Ar, H2, GH4 and N2
S o lu tio n s in Airs Air C a r r ie r
...................................163
continued
xi

LIST OF TABLES ~ Continued
TABLE

Page

XVI

Response to $Q Mlo I n j e c t io n s of Methane S o ltu io n s i n '
Argons Ar (* 0 2) Ca r r i e r . . * * * * . * * . * . . * * * * . . * . . * .............* • • .............16U

XVII

Response t o Methane in Ar(+02) C arrier w ith 12:1 Stream
S p l i t t i n g R a t io 0000**000 ooo*®************. *©. *. ****■#-*■•***.** 16^

XVIH

Response t o $Q Ml* I n j e c t io n s of A ir S o lu tio n s in Argonj
Ar (*>Q2) C a r r ie r
.......... *............... 166

x ii

LIST OF FIGURES
FIGURE

Page

1 * S c h u le r l s Apparatus f o r E x c ita tio n o f Organic M olecules in
th e Glow D isch arge . . . . . . . ....................... . . . . . . . . ...................................

1U

2. Flow System f o r O bservation o f Glow D isch arge E m ission
S p e c tr a U sing a C arrier Gas and High Frequency E x c i t a t i o n . ..

36

3* E m ission Spectrum o f Benzene E xcited w ith Argon C arrier Gas.

50

U. Flow System f o r O bservation o f Glow D isch arge E m ission S p e c tr a w ith o u t a C arrier Gas........... ...................................

58

5* T e sla D ischarge D e te c to r f o r Gas Chromatography............... . . . . . .

90

6 . E l e c t r i c a l C ir c u its Used w ith T esla D isch arge D e te c to r s fo r
Gas Chromatography
....................

95

7 . Flow System Used w ith T esla E x cited Glow D ischarge
D e t e c t o r s ....................

98

8 . D e te c to r Current v s .

Applied V oltage; A ir C a r r ie r ....................

116

9» D e te c to r Current v s . P ressu re f o r N itrogen; A ir , Argon and Helium C arrier G a ses
................ ............................ *.......................119
1 0 . Methane and Helium S o lu tio n s i n A ir , A ir C arrier; Response
v s • P r e s s u r e ...........
1 1 . Response t o l±9.3 Volume P ercen t Hydrogen S o lu tio n in A ir;
A ir C a r r i e r . . . . .
1 2 . Response t o 20 Ml. I n j e c t io n s o f Various S o lu tio n s in A ir;
..................
A ir C a r r ie r

121
* 122
12li.

1 3 . Response t o $0 M l. I n j e c t io n s o f Methane S o lu tio n s in
Argon; Argon C arrier w ith Oxygen S c a v e n g e r .
............................129
1U» Response to Methane in Argon C arrier w ith Oxygen S caven ger;
1 2 s 1 Stream S p l i t t i n g R a tio
.............

131

15* Response t o 50 M l. I n j e c t io n s o f Air-Argon S o lu tio n s ; Argon
C arrier w ith Oxygen S ca v en g er.................

135

1 6 . Chromatograms U sing th e T esla D isch arge D etecto r; Argon
C arrier w ith Oxygen S caven ger
...............................

137

17 . A M e c h a n ic a l-E le c tr ic a l T ransducer..................

li^ l

x iii

INTRODUCTION
Ao G eneral Course o f th e Work
Much o f ch em istry i s concerned w ith th e c h a r a c te r iz a tio n and
p r o p e r tie s o f su b sta n ces as th ey occur a t room tem perature or a t moderate
tem peratureso

Under such c o n d itio n s * m olecu lar s p e c ie s are alm ost

e x c lu s iv e ly i n th e low er v ib r a t io n a l l e v e l s o f t h e ir ground e le c t r o n ic
sta te so

We know r e l a t i v e l y v ery l i t t l e about e x c ite d e le c t r o n ic s t a t e s

o f m olecu les and m olecular fragm ents or about m olecu lar i o n s •

It is

n a tu r a l th a t our d e s c r ip tio n s o f chem ical r e a c tio n s are based la r g e ly
upon con cep ts a s s o c ia te d w ith th e m uch-studied ground s t a t e s o f m o le c u le s.
However* chem ical r e a c tio n s g e n e r a lly occur on ly among th e few m olecu les
o f e x c e p t io n a lly h igh energy in th e r e a c t in g system* and we commonly
employ d e s c r ip t io n s o f r e a c t io n mechanisms in v o lv in g s tr u c tu r e s probably
more n e a r ly r e la t e d t o th e e x c ite d e le c t r o n ic s ta t e s * or io n iz e d s ta te s *
th a n t o th e normal ground s t a t e s .

Furthermore* th e r e i s in c r e a s in g

i n t e r e s t in r e a c tio n s a t v ery h igh tem peratures or r e a c tio n s induced by
io n iz in g ra d ia tio n s* which u n q u estion ab ly proceed in p art through
e l e c t r o n i c a l l y e x c ite d or io n iz e d s tr u c t u r e s .

I t th e r e fo r e seems most

d e s ir a b le to ex p lo re p o s s ib le paths o f resea rch which can fu r n ish in fo r ­
m ation about th e lesser-k n o w n ch em istry o f e x c ite d m olecules* m olecular
fragm ents* and m olecu lar io n s .

The p resen t in v e s t ig a t io n r e p r e se n ts

an e x p lo r a to r y to u r along one of th e s e paths s t r e s s in g th e a p p lic a tio n
o f r e l a t i v e l y sim p le ex p erim en tal tech n iq u es and a v a ila b le equipment

1

2

t o o b ta in in fo rm a tio n o f a ty p e h e r e to fo r e a c c e s s ib le o n ly through u se
o f more complex s p e c ia l apparatuso
The p o s s ib le a rea s o f in v e s t ig a t io n which can fu r n is h more or l e s s
d ir e c t in fo rm a tio n on e x c ite d m o lecu les and m olecu lar io n s a re ph oto­
ch em istry (in c lu d in g f la s h p h o t o ly s is ) , r a d ia tio n ch em istry, mass
sp e c tr o sc o p y , shock and d e to n a tio n w aves, a b so rp tio n sp e c tr o sc o p y ,
m olecu lar e m issio n sp e c tro sco p y and e l e c t r i c a l d isch a rg e s t u d i e s .
R e la t iv e ly l i t t l e a t t e n t io n h as been g iv en by chem ists to th e chem ical
r e a c tio n s and s p e c tr a em itted by e l e c t r i c a l d is c h a r g e s •

The r e c e n t

in v e s t ig a t io n s o f S ch u ler and o th ers have in d ic a te d th e f r u it f u ln e s s o f
em ploying some o f th e s e te c h n iq u e s, and th e p o s s i b i l i t y o f c o n t r o llin g
th e maximum l e v e l o f energy reached in th e d isc h a r g e .

The tech n iq u e

employed in t h is I n v e s t ig a tio n i s a com bination o f a sim p ler, l e s s c o s t ly
T e s l a - c o i l method o f o b ta in in g d isch a rg es a t c o n tr o lle d energy l e v e l
w ith th e u se o f a p h o t o e le c t r ic reco rd in g spectrophotom eter f o r r a p id ly
mapping out th e observed s p e c tr a .
In th e background s e c t io n , th e g en era l p r o p e r tie s o f glow d is ­
charges w i l l f i r s t be d is c u s s e d , fo llo w e d by a summary o f p e r tin e n t
fundam ental p r o c e s se s o ccu rrin g in g a s e s .

A review o f p e r tin e n t

ch em ical and s p e c tr o s c o p ic s tu d ie s em ploying glow d isc h a r g e s w i l l be
g iv en in th e f i r s t s e c t io n o f P a rt I .

The exp erim en tal arrangement

used In t h i s i n v e s t ig a t io n , and th e r e s u lt s o b ta in ed , w i l l th en be d i s ­
cussed i n P a r t I .

As an outgrowth o f th e o b se rv a tio n s on th e p r o p e r tie s

o f T e sla -g lo w d isc h a r g e s d escrib ed in P a rt I , a new a p p lic a tio n o f th e
T e sla -g lo w d isc h a r g e t o d e t e c tio n in gas chromatography was developed
and w i l l be d escrib ed in P art I I .

3

Bo P r o p e r tie s o f th e Glow D isch arge
The glow d isch a r g e c o n s is t s c h i e f ly o f two p o r tio n s , th e p o s it iv e
column and th e n e g a tiv e glowo

The p o s i t i v e column o f a glow d isch a rg e

betw een e le c tr o d e s in a p a r t i a l l y evacuated d isch a rg e tube i s th e la r g e
luminous p o r tio n o f th e d isch a rg ee

I t i s c h a ra cterized by a r e l a t i v e l y

sm a ll p o t e n t ia l g ra d ien t and c o n s is t s o f slow moving p o s it iv e ion s
to g e th e r w ith f a s t e r moving e le c tr o n s so th a t th e r e i s a n et p o s it iv e
charge in th e column.

Almost th e e n t ir e p o t e n t ia l drop in th e d isch a rg e

occurs In th e r e g io n near th e cathode c a lle d th e cathode or n e g a tiv e
glowo

E le c tr o n s are r e le a s e d from th e cathode by p o s i t iv e io n bombard­

ment o This i s th e p r o ce ss c a lle d secondary em ission,,

Secondary

e le c t r o n s are low in en ergy, but th e p o s it iv e io n f i e l d a c c e le r a te s
them and th ey th en produce more ion s and e le c tr o n s in c o l l i s i o n s .
E le c tr o n s a c c e le r a te d from th e cathode through th e p o s it iv e column
a t t a i n e n e r g ie s which are p r o p o r tio n a l t o th e r a t io o f th e e l e c t r i c
f i e l d in th e column t o th e p ressu re in th e d isch a rg e sp a c e.

For a given

su b sta n ce b ein g e x c ite d in th e glow discharge^ however, th e p o t e n t ia l
drop a cro ss th e d isch a rg e i s p r a c t i c a lly co n sta n t f o r a wide range of
cu rren t f le w .

This i s known as th e wnormal glow® and i s th e typ e o f

d isc h a r g e o f i n t e r e s t in t h i s work.
For th e d ir e c t cu rrent glow d isc h a r gef in te r n a l e le c tr o d e s are
n e c e ssa r y t o sup p ly e le c tr o n s to th e d isch a rg e to make i t m aintain
i t s e l f o Low freq u en cy a lte r n a tin g current i s v ery s im ila r to d ir e c t
cu rren t f o r e x c it in g a glow d is c h a r g e .

I t i s p o s s ib le a ls o to o b ta in

1*

a d isc h a r g e which has th e p r o p e r tie s o f a glow d isch a rg e w ith ou t th e
u se o f in te r n a l e le c tr o d e s <> This i s accom plished by u sin g a h ig h
freq u en cy e x c it e r o f some s o r t .

R adiofrequency or microwave energy may

be coupled t o th e d isc h a r g e through g la s s w ith o u t in t e r n a l c o n n e c tio n s.
The e le c tr o n s f o r i n i t i a t i o n o f th e d isch a rg e are to rn from th e w a ll o f
th e d isc h a r g e tu b e , but b ecau se o f th e rap id a lte r n a t io n o f th e f i e l d ,
s u f f i c i e n t e le c t r o n s and io n s fo r s u s ta in in g th e d isch a rg e are formed
by th e o s c i l l a t i n g e le c t r o n s , whereas in a d ir e c t cu rren t d isch a rg e
e le c t r o n s s t a r t in g from th e cathode must have s u f f i c i e n t energy t o make
up f o r a l l l o s s e s in th e d isch a rg e and can o n ly t r a v e l in a d ir e c t io n
away from th e cathode.,
e le c t r o n s o u r c e .

This r e q u ir e s an in te r n a l e le c tr o d e as an

B ecause o f th e convenience o f e le c t r o d e le s s o p e r a tio n ,

i t has been used w id e ly and much o f th e work d isc u sse d w i l l be o f th a t
ty p e o
Co E le c tr o n Impact E x c ita tio n in th e Glow D isch arge
S p ectra in th e glow d isch a rg e are e x c ite d p r im a r ily by e le c tr o n
im pactj th e tech n iq u e f o r o b ta in in g em issio n s p e c tr a of polyatom ic
s p e c ie s a t c o n tr o lle d e x c it a t io n energy has been termed '*e le c tr o n impact
e x c it a t io n in th e glow d isch a r g e •*. This term in ology and th e fo llo w in g
b r i e f d e s c r ip t io n o f th e mechanism o f th e e x c it a t io n p ro cess are due t o
S c h u le r , who has l a r g e l y developed th e f i e l d o f m olecular em issio n
s p e c tr o sc o p y .
S ch u ler and Reinebeck ( 1 ) have assumed th a t b ecau se th e spark l i n e s
o f th e gas p r e se n t occur o n ly v e r y w eakly in th e p o s i t i v e column, th e

5

f i r s t io n iz a t io n p o t e n t ia l o f th e gas must r e p r e se n t an upper energy
l i m i t fo r most of th e e le c t r o n s in th e d isch arge*

Furtherm ore, i t can

be presumed th a t a t th e f i r s t e x c it a t i o n p o t e n t ia l o f th e gas th e
e le c t r o n energy d is t r ib u t io n drops o f f sharply, s in c e e le c t r o n impact
w ith atoms now can be i n e l a s t i c , and an e le c t r o n w i l l be robbed o f i t s
energy by a gas atom b e fo r e th e e le c t r o n energy can reach an extreme
v a lu e o The n e t r e s u lt i s th a t in th e p o s i t iv e column o f th e glow d is ­
charge th e r e are p resen t e le c tr o n s in an energy d is t r ib u t io n f a l l i n g
o f f sh a r p ly a t th e f i r s t e x c it a t io n p o t e n t ia l o f th e gas atoms p r e se n t,
to g e th e r l a r g e ly w ith n e u tr a l, e x c ite d gas atoms and a few gaseous io n s ,
few o f which are e x c ite d above th e ground s t a t e o f th e io n .

A ll o f

t h e s e s p e c ie s may be a c t iv e i n e x c it a t io n o f f o r e ig n m olecules in tr o ­
duced in to th e system*

A b r ie f review o f work done in th e f i e l d of

glow d isc h a rg e e m issio n s p e c tr a and some r e la te d f i e l d s i s p resen ted
in th e f i r s t s e c tio n o f P art I*
D* Summary o f P r o c e sse s Taking P la c e
in th e Glow D isch arge
The im portant p r o c e sse s ta k in g p la c e in th e glow d isch a rg e w i l l be
summarized b r ie f ly *
l ) D ir e c t e x c i t a t i o n by e le c t r o n impact*
e

* M — "ft* iyf

e

(low er K*S*)

At in te r m ed ia te f ie ld - t o - p r a s s u r e r a t io s (from perhaps 2 to
100 v o lts/c m o /iH o Hg) t h i s type o f p ro cess accounts f o r a major
f r a c t io n o f th e energy lo s s e s su ffe r e d by e le c t r o n s .

E lectro n

impact e x c i t a t i o n obeys th e Franck-Condon p r in c ip le , and th e

6

e x c i t a t i o n may lea d e it h e r t o a s t a b le e x c ite d s t a t e or to
d i s s o c i a t i o n in to fragm en ts, depending upon r e l a t i v e d is p la c e ­
ments o f p o t e n t ia l energy s u r f a c e s .

U nlike o p t ic a l e x c it a t io n ,

e le c t r o n impact o f s i n g l e t m o lecu les can lea d e it h e r t o s in g l e t
or t o t r i p l e t e x c ite d s t a t e s °
2) I o n iz a tio n by e le c t r o n impact*
e

M

■>- M + 2e

At h ig h er f ie ld - t o - p r e s s u r e r a t io s t h i s type o f p ro cess becomes
in c r e a s in g ly im portant * I t i s , o f cou rse, str o n g ly dependent
upon th e io n iz a t io n p o t e n t ia l o f th e m olecular s p e c ie s .

In

t h is ty p e o f p r o c e s s , a s in g le e le c t r o n c r e a te s a new io n p a ir
( io n p lu s electron ).? th e ea se o f form ation o f io n p a ir s by
e le c t r o n impact i s exp ressed through th e f i r s t Townsend co­
e f f i c i e n t , a , which g iv e s th e number o f io n p a ir s produced by
a s in g le e le c t r o n t r a v e r s in g one cm. in th e f i e l d d ir e c t io n
a t a p p rop riate f ie ld - t o - p r e s s u r e r a t i o .
3 ) I o n iz a tio n p lu s e x c it a t io n by e le c tr o n im pact.
e“ * M— *

M** + 2e“

Higher energy e le c tr o n s may produce e x c ite d s t a t e s o f i o n s .
U) R a d ia tiv e recom b in ation o f ion s and e le c t r o n s .
a
e “ * M* —

[M*] — >

M# hv

This p ro cess o f d ir e c t com bination o f io n s and e le c tr o n s to
-1 2

form e x c ite d m olecu les i s of v e r y low p r o b a b ility ( a . ~iQ GIQ3
io n -s e c
becau se th e d u ra tio n o f th e io n -e le c tr o n encounter i s so

7

b r i e f in com parison to th e mean l i f e t i m e o f e x c it e d e le c t r o n ic
sta te s o

The e x c e ss energy can most l i k e l y n ot be l o s t b efo r e

th e io n p a ir ag a in d i s s o c i a t e s * The p ro cess becomes in c r e a s in g ly
improbable fo r more e n e r g e tic e le c t r o n s .

The r a d ia tiv e recom bi­

n a tio n c o e f f ic ie n t * tte r * i s th e s p e c i f i c r a te co n sta n t f o r th e
recom b in ation p r o c e s s .
5 ) D is s o c ia t iv e recom bination o f io n s and e le c t r o n s .
* a ed
*
8” * M -------> A * B
The recom b in ation p ro cess i s g r e a tly f a c i l i t a t e d by p o s s ib le
bond rupture* which would make p o s s ib le th e d is s ip a t io n o f some
o f th e energy o f th e recom b in ation .

S in ce d i s s o c i a t io n can

occur w it h in a v ib r a t io n a l period ( ^ 1 0

s e c . ) w h ile e m issio n
8

o f e le c t r o n ic energy i s u s u a lly much slow er ( ^ 10

sec.)*

d i s s o c i a t i v e recom bination p r o c e s se s tend t o be about a m illio n ® cm3
f o ld as p robable as r a d ia tiv e recom bination ( a , /“v-/ 10
).
^
v ed
io n - s e c .
—»

Lew en ergy (th erm a l) e le c tr o n s are again most r e a d ily captured
by io n s .

Because io n iz a t io n p o t e n t ia ls are a p p recia b ly higher*

in general* than bond en erg ies* one o f th e d is s o c ia te d fragm ents
w i l l u s u a lly carry e le c t r o n ic e x c ita tio n * which can lead t o
subsequent e m iss io n .

The d is s o c ia t i v e recom bination c o e f f ic ie n t *

a e(j* i s th e s p e c i f i c r a te co n sta n t fo r t h is recom bination
p rocess.
6) W all recom bination (am bipolar d if f u s io n ) .
e

,,*0* w a ll
♦ M — ----- >

M

The w a ll can se r v e to d is s ip a t e th e e x c e ss energy o f recom bi­
nation* and hence a c ts as an io n - e le c t r o n s in k .

D if fu s io n o f

8

th e charged s p e c ie s to th e w a lls o fte n p r im a r ily determ ines
th e amount o f i n i t i a t i o n n e c e s s a iy t o s u s t a in th e glow d is c h a r g e .
7 ) Ion rearrangem ent.
M* — >

A* * Bo

Ions i n i t i a l l y formed by e le c t r o n impact may undergo subsequent
rearrangem ents w ith in a few v ib r a t io n a l p erio d s b e fo r e s u s t a in ­
in g c o l l i s i o n s w ith e le c tr o n s or oth er s p e c ie s -

The rearrange­

ment may be an iso m e r iz a tio n or a fragm en tation t o produce a
new io n and, u s u a lly , a f r e e r a d ic a l-

( I t should be remembered

th a t th e primary io n s formed from s in g l e t or t r i p l e t m olecu les
are n e c e s s a r ily io n - r a d ic a ls , s in c e th e y p o s s e s s an odd e le c t r o n
as w e l l as a p o s i t i v e charge )„ The rearrangem ents which occur
are g e n e r a lly th o se in v o lv in g r e l a t i v e l y l i t t l e en ergy, and are
in c r e a s in g ly l i k e l y where some e x c e ss energy in form ation o f
th e io n went in to v a r io u s v ib r a t io n a l modes.
8) Charge t r a n s f e r M * A* — >

A *

M*

Ions o f h ig h e r io n iz a t io n p o t e n t ia l s p e c ie s may, upon c o l l i s i o n ,
remove e le c tr o n s from s p e c ie s o f lower io n iz a t io n p o t e n t ia l.
■Where a p p re cia b le d iff e r e n c e in io n iz a tio n p o t e n t ia l e x i s t s ,
some e le c t r o n ic e x c it a t io n may accompany th e charge t r a n s f e r .
9 ) I o n iz a t io n by e x c ite d atom s.
AA +

M

A *

M* ♦

e

The energy o f e x c it a t io n of a s p e c ie s may produce io n iz a t io n
o f a s p e c ie s having io n iz a t io n p o t e n t ia l low er than th e

9

e x c it a t io n energyo

In gases a t f a i r l y low pressure* i t i s

u n lik e ly th a t e l e c t r o n i c a l l y e x c ite d s p e c ie s w i l l undergo
c o l l i s i o n p r io r t o ra d ia tio n * u n le s s th e e x c ite d s p e c ie s be
m e ta sta b le (hence* l o n g - l i v e d ) .
Am * M

5* A ♦ M* ♦ e" (th e Penning e f f e c t )

1 0 ) E x c it a t io n by e x c ite d atom s.
A" * M — >

it ♦ A

E le c tr o n ic energy may be tr a n sfe r r e d on c o l l i s i o n between
e x c ite d and normal s p e c i e s .

M etastable atoms are again most

l i k e l y t o be im portant h e r e .
11} Complex io n fo rm a tio n .
M* *

B ----- >

MB'*

Ions may complex w ith n e u tr a l s p e c ie s t o form la r g e r io n s .
This p ro cess i s f a c i l i t a t e d by th e p o la r iz in g e f f e c t o f th e ion*
and may be enhanced by th e r a d ic a l nature o f ion s formed from
s i n g l e t atoms or m olecules* p a r t ic u la r ly in in t e r a c t io n w ith
d o u b let or t r i p l e t n e u tr a l s p e c ie s .

T his process* fo llo w ed by

d i s s o c i a t i v e recom bination* a ffo r d s a tw o -ste p mechanism f o r
e le c t r o n ic e x c it a t io n o f n e u tr a l s p e c ie s* s t a r t in g w ith th e
corresponding i o n s .
12) E lec tro n c a p tu re.
M# e

M

The capture o f an e le c t r o n by a n e u tr a l s p e c ie s t o form a n e g a tiv e
io n

i s in g en era l a p ro cess of low p r o b a b ility * ex cep t f o r v e r y

slow (th erm a l) e le c tr o n s combining w ith m olecu les of h igh e le c tr o n
a ffin ity «

10

13) Quenching p r o c e s s e s „
Any p ro c ess in which a s p e c ie s o f d ir e c t in t e r e s t or importance
i s d estro y ed may be con sid ered a quenching p r o c e s s .

Thus,

p r o c e s se s ( 8 ) , ( 9) and ( 1 0 ) , in p a r t ic u la r , may a c t t o quench
th e co n c e n tr a tio n s o f m eta sta b le atoms or of io n s e s s e n t i a l
t o th e phenomenon o f i n t e r e s t »
1U) E le c tr o d e p r o c e s s e s •
Many p r o c e s se s which occur a t th e e le c tr o d e s or a t su r fa c e s of
probes g r e a t ly a f f e c t th e e le c tr o n and io n com p osition o f th e
vapor in a glow d isch a rg e <, These may in c lu d e th erm ionic
e m issio n o f e le c t r o n s , f i e l d em issio n o f e le c tr o n s (where stron g
p o t e n t i a l g ra d ie n ts e x i s t in th e v i c i n i t y o f m etal s u r f a c e s ) ,
secondary em issio n p r o c e sse s ( p a r t ic u la r ly in p o s i t iv e io n
bombardment a t th e cath ode, d escrib ed through th e second
Townsend c o e f f i c i e n t ) , and p r e f e r e n t ia l e le c t r o n capture
(through th e g r ea te r v e l o c i t y of th e li g h t e r e le c tr o n s as com­
pared t o th e h e a v ie r p o s it iv e io n s at a p a r t ic u la r e f f e c t i v e
tem perature) <= M etal e le c tr o d e s to which a p o t e n t ia l i s a p p lied
tend t o b u ild up about them in th e gas phase a h ig h er concen­
t r a t io n o f charge c a r r ie r s o f o p p o site s ig n i t h is c r e a te s a
r e g io n of '*space charge11 about th e e le c tr o d e *
15) P hotochem ical p r o c e s s e s «
The l i g h t em itted in th e d isc h a r g e , p a r t ic u la r ly th e sh ort
w avelen gth p o r t io n s , may be absorbed and cause e x c it a t io n ,
p h o to d is s o c ia t io n , or p h o to io n iz a tio n o f gaseous s p e c ie s , and
p h o t o e le c t r ic e m issio n from m etal s u r f a c e s ■>

11

1 6) Chemical p r o c e s s e s .
The i o n ic and f r e e r a d ic a l s p e c ie s produced in th e glow d i s ­
charge may engage in a v a r ie t y o f secondary chem ical r e a c tio n s
which can s i g n i f i c a n t l y a f f e c t th e com p osition o f th e d is ­
charge medium.

Of p a r t ic u la r im portance are r a d ic a l a b s tr a c tio n ,

a d d itio n , and recom bination r e a c t io n s , which can be in volved
in ch ain sequences producing c o n sid era b le chem ical change from
each r e a c t iv e s p e c ie s produced

P o ly m eriza tio n r e a c tio n s

commonly occu r, and r e s u lt in d e p o s itio n o f high m olecular
w eigh t m a te r ia ls on th e in s id e s u r fa c e s o f th e d isch a rg e tu b e .
Extended trea tm en ts o f p r o c e sse s occurring i n a gaseous d isch arg e
may be found in a t r e a t i s e by Loeb ( l ) and work by Penning ( 2 ) .

PART I
MOLECULAR EMISSION SPECTRA AND CHEMICAL REACTIONS
IN THE GLOW DISCHARGE

TABLE OF CONTENTS
Page
Ao A Review o f Clow D isch arge E m ission S p ectra and R elated F ie ld s .

12

1 . E m ission S p ectra o f P olyatom ic M olecules and I o n s . . *
a . E a rly Work
bo The Technique"and Work o f H. S c h u le r .
(1 ) The B a sic Technique
O 0 0 O 0 0 O O O 0 O 0 0 O
(2 ) Mechanism o f E x c ita tio n in th e Glow
D isch arg e . . o . . o . o o o o . . . . . o.
. . . o». •««•
( 3) R efinem ents o f th e Technique Which Aid in
I d e n t if y in g S p e c tr a l E mi t t e r s . . . . . . . . . . . .
(U) New S p ectra Observed by th e S ch u ler TechniCJU©
(5 ) L im ita tio n s o f th e T echnique. . . . . . . . . . . . •
Co R e su lts from Other Techniques o f Glow D ischarge
E x c it a t io n o f M olecular E m ission S p ectra O © 0 0 0 O 0 0 0 0
2 . S tu d ie s o f R ea ctio n Mechanisms in th e Glow D ischarge
o o o
a o G eneral . . .
b o Chemical A n a ly sis o f P r o d u cts.
Co S p e c tr o sc o p ic E m ission S tu d ie s
3 . Other S ou rces o f E le c tr o n Impact E x c ita tio n
' 0 0 © 0 0 0 0 0 0 0 0 6 0 0 0 0 * 0
ao I o n iz in g R a d i a t i o n . . . . . .
b . The Mass Spectrograph a o o o o 0 « 0 0 0 * O 0 0 0 0 0 0 0 O * * 0 0

12
12
13
13

0 0 0 0 0 0 0 0 0 0 0 0 0 6 0

0 d O C O O 0 0 0 4 O 0 0 0

o

O O O O O O O

O O O O O O O O o O O O O O O O

OO O0 O0

0 Q O O O 0 O O Q O © © *

.

0

o

0

.

0

0

0

0 6 0 0 0 0

0

0

0

0

c o o o

QCOO

0 6 * 6

0 6 0 0 0 0 0 0 0 0

0 0 OQO0 0 0 0 O0

Bo E m ission S p ectra in a Flow System w ith a C arrier Gas

0 0 * 0 0 0 0

o

o

0 * 0 0 0 0 0 0 *

o

0

0 0 0 0 * 0 0 6 0 0

o 0 0 0 6 0 0 0 0 0 0 0 0

a

o

O O O O O O O

O O O 0 0 O

O 0

*

© 6 0 0 0 0 0 * 0 0

6 0 0 0 0 * 0 0 0 6 0 6 0 0 0

0 0 0 0 *0

00

0 0 0 0 0 0 0 0 0 0 0 0 0 6 0 0 0 6 0 0 0 0 6 0 0 0

O O O O 6 6 0 6 O 0 O O 6 O O O 0 0 O O O 0 0 0 O O 0 O O

* 0 * 0 0 0 0 * 0 6 0 ©
0 6 0 * 0 6 0 0

0 0 0 0 6 6 0 0 0 0 0 0 #

000

0 0 0 * 0 0 6 0 0 0 0 6 6 0 0 0 0 0
© 0 0 0 0 6 0 * 0

19
20
22
23
25
25
26
27
29
29
30
31

0 0 0 O

0 0 0 0
3.o E xperim ental
a . G eneral D e s c r ip tio n o f E xperim ental Approach
b . Reagents o o o 0 « O O 0 O o c o
0 0 0 0 0 0 0 * 0 0 0
O O • 6 * 0 0 0 0 6
(1 ) A r g o n . . . .
( 2) He l i u m. . .
( 3) Organic Samples
c . Apparatus
(1 ) D isch arge S y ste m .. . o . ,
60 0 6
( 2) O p tics and Sp ectrophotom eter.
6 6
(3 ) The E x c ite r
d o E xperim ental Procedure
O O O
(1 ) W avelength Measurement
(2 ) O perating th e D ischarge S y s t e m ...
2 . R e su lts and D i s c u s s i o n . . . .
a . Quenching o f th e Argon S p ectru m .. . .
6 0 0
b . The Blue Spectrum o f A r g o n ... O O O O O C 0
Co C o r r e la tio n o f th e Observed Blue Spectrum w ith th e
B lue Spectrum of A r g o n . . . . . .
O O O O O O O O O O O *

16

0 0 0 6 0

0 0 0 0 0 * 0 0 0 0

OO

continued

31
31
32
32
33
33
3k
3k
37
38
UO
UO
bO
b3
k3
hS
U6

TABLE OF CONTENTS - Continued
Page
d o Helium C arrier Gas . . . . . . . c * . . . . . . . . . . . . . . . ...................
e « P olyatom ic M olecular S p ectra . . . . . . . . . . . . . . * . ..............
f * I n te r p r e ta tio n o f S e le c t iv e Quenching o f th e Argon
Red S p ectru m *................................................
3o S u g g e stio n s f o r Further Work w ith Argon C arrier G a s , . * . * .
a* E f f e c t o f th e Nature o f E x c it a t io n on E le c tr o n
E n erg ies in th e D ischarge . . . . . . . . ......................
b . R e la tiv e E f f e c tiv e n e s s o f Various Quenchers................

U6
h9

9h
55

C. E m ission S p ectra in a Flow System w ith ou t a C arrier G a s . . . . . . . .

57

1 . E xperim ental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
a o Gener a l o o . o o . . e o .
.....ao.....................
b *. M o d ifica tio n s o f P revious A pparatus
..............
c . Procedure During a Run
............... . . . . . . . . .
2 . R e su lts and D is c u s s io n
............
a . K etones . . . . . . c . * . . . . o. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
b * A lco h o ls y Alkanes and A lk y l H alid es
.........
c . I n te r p r e ta tio n o f D ecom position P a t t e r n s . . .................
(1 } Ge n e r a d _ . . . o . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
( 2) A lc o h o ls , Adkanes, A ceto n e......................
(3 ) A lk y l H a l i d e s . . . . . . . . . . . ......... .. 0. . . . . . . . . . . . .
3 * Summary o f Work w ith ou t a C arrier Gas
............
1±. S u g g estio n s fo r Further Work W ithout a C arrier Gas..............

57
57
57
60
61
61
63
67
67
67
72
7U
75

h9
5U

Ao A Review o f Glow D ischarge E m ission S p ectra
and R elated F ie ld s
1 ” E m ission S p ec tra o f P olyatom ic M olecules and Ions
a o E a rly Work
E a rly work in e l e c t r i c a l e x c it a t io n o f e le c t r o n ic sp e c tr a o f p o ly ­
atom ic m o lecu les was done by MeV ick er, Marsh and Stew art (U) and Marsh
( 5 ) b eg in n in g in 1923.

Organic vapors were caused t o flo w through a

p a r t i a l l y ev a cu a ted , g la s s e n c lo se d , space betw een c o n c e n tr ic c y lin d r ic a l
e le c t r o d e s connected t o th e secondary w inding o f a T e sla tran sform er
h avin g an output o f s e v e r a l thousand v o l t s .

The spectrum o f th e glow

d isc h a r g e ob tain ed was th en observed end-on down th e c y lin d r ic a l vapor
sp a ce o Benzene vapor was observed t o em it bands in th e 3000 A r e g io n
w hich were c o r r e c t ly i d e n t i f i e d as em issio n o f th e benzene m olecu le
betw een th e same e le c t r o n ic s t a t e s as th e ab so rp tio n o f t h is m o le cu le .
Other benzenoid m o lecu les were observed t o behave s im ila r ly .
o f carbon and hydrocarbon polymers was always p r e s e n t .

D e p o sitio n

In th e ca se o f

a ceto n e and a n i l i n e th e d ecom position was so sev ere as to p reclu d e
o b se r v a tio n o f e m issio n by any polyatom ic s p e c ie s .
In 1930, A u stin and Black (6 ) continued work along th e l in e s th a t
McVicker, Marsh and S tew art had p u rsu ed .

U sing e x te r n a l e le c tr o d e s and

v e r y h igh v o lta g e s (ap p roxim ately 100,000 v o l t s ) as w e ll as high cu rren t
d e n s itie s ^ th e y were tro u b led w ith stro n g d ecom p osition and crack in g o f
th e g la s s d isc h a r g e t u b e s .

These authors th en began u sin g in te r n a l

e le c tr o d e s w ith th e same h igh p o t e n t i a l s .

U sing h ig h er d is p e r s io n than

th e p re v io u s a u th o r s, A u stin and Black q u ite c le a r l y e s ta b lis h e d th e

12

68

in th e s e m o le c u le s, alth ou gh C2 i s observed r e a d ily from d eco m p o sitio n
o f hexane or many a lk y l h a lid e m o le c u le s .
An in t e r p r e t a t io n o f th e p e r s is t e n c e o f t h e C-0 bond can b e made by
e x te n sio n o f th e g en er a l mechanism f o r e le c t r o n im pact e x c i t a t i o n o f
a lc o h o ls proposed by Cummings and B leak n ey (5 2 ) and d e s c r ib e d e a r l i e r
in th e review m a te r ia l, S e c tio n I .

In th e i n i t i a l e le c t r o n im p act, a

non-bonding oxygen e le c t r o n i s removed from th e a lc o h o l, and th e r e s u lt in g
m olecu le c o n ta in s an oxygen w ith a p o s i t i v e charge and an odd e le c t r o n .
The oxygen see k s t o com pensate f o r i t s e le c t r o n d e f ic ie n c y b y form ing an
a d d itio n a l v a le n c e bond w ith th e carbon atom t o which i t i s a lrea d y
bound.

The most w eak ly bonded s u b s t it u e n t i s n orm ally e j e c t e d t o do t h i s .

In th e a l i p h a t i c a lc o h o ls , th e s u b s tit u e n t e j e c t e d w i l l , in g e n e r a l, be an
a lk y l group.

E ith er th e i n i t i a l io n or a rearranged fragm ent io n may

undergo d i s s o c i a t i v e recom b in ation t o form e x c it e d and norm al fragm en ts.
In a d d itio n , d ir e c t e x c i t a t i o n o f th e v a r io u s s p e c ie s may le a d t o r a d ia tiv e
s t a t e s , or t o u n sta b le e x c it e d s t a t e s which d i s s o c i a t e , and numerous
secondary r e a c tio n s in v o lv in g th e r e a c t iv e fragm en ts may o c c u r .

Some o f

th e im portant p r o c e s se s are shown in th e complex r e a c t io n scheme b elow .
R
R - C - OH * e'
H

H

©
R - C - 0 - H

D is s o c ia t iv e
Recomb.

e

D i s s o c ia t iv e
Recom bination,

Q_

CO

Cl .

APPARATUS

LL)

c
o

CO

co

o
LU

Cu

FOR EXCITATION OF ORGANIC
THE GLOW
DISCHARGE

MOLECULES

o

v

UJ

SCHULERS

co

IN

o '

1.

O

FIGURE

iu

CL?

co

9CJ ,9LO

UJ

15

The d isc h a r g e tu be con tain ed a gas n on -con d en sib le a t liq u id a ir
tem perature—’f o r exam ple, a ra re gas* hydrogen, or n itr o g e n a t a p ressu re
o f a f r a c t i o n o f a m illim e te r o f m ercury.
th e c a r r ie r g a s .

T his gas was r e ferred t o as

Sample vapors were caused t o flo w in t o th e system from

th e v o l a t i l e sample in a c o n ta in e r , C, through th e d isch a rg e space S ,S S
in t o th e liq u id a ir tra p s T, T 9 <> The r a te of flow o f th e sample was
c o n tr o lle d by c o n t r o llin g i t s vapor p ressu re through v a ry in g th e
tem perature o f th e sample w ith a cold b a th .

The vapor p ressu re in th e

d isc h a r g e space could a ls o be c o n tr o lle d by e n c lo s in g i t i n an oven.
With t h i s arrangement th e o rgan ic vapors do n o t come in co n ta ct w ith th e
e le c t r o d e s , and d eco m p o sitio n , which i s always g r e a te s t in th e v i c i n i t y
o f th e e le c t r o d e s , i s p r a c t i c a l ly e lim in a te d .

The glow d isch a rg e i s

conducted through th e cold t r a p s , th e energy b ein g tr a n sfe r r e d from the
c a r r ie r gas t o th e sample vapor i n th e t r a p s .

The spectrum o f th e glow

d isc h a r g e i s observed end-on through th e windows W, W8 o f th e d isc h a r g e
space S , S 8 .

The d isch a rg e sp ace i s in e f f e c t th e p o s i t i v e column o f

a glow d isc h a r g e , s in c e w ith th e symmetry o f th e system th e a lte r n a tin g
cu rren t m erely changes d ir e c t io n of the cu rren t flo w p e r io d ic a lly .
As an example o f how th e system o p erates in p r a c t ic e , l e t us con­
s id e r th e s it u a t io n where helium i s th e c a r r ie r gas and to lu e n e i s th e
sam p le.

I f th e sample i s a t f i r s t c lo se d o f f from the d isch a rg e space

and th e e le c tr o d e s a c t iv a t e d , th e arc spectrum l i n e s o f helium are th e
predominant components o f th e observed spectrum .

I f th en th e sample

stop cock i s opened, b u t th e sample co ld bath i s a t a low enough tem perature
t o keep th e p a r t i a l p r e ssu r e o f to lu e n e so low th a t th e helium i s in

16

e x c e s s by th e r a t i o o f about 3 0 s1 , d iatom ic fragm ents such as C2 and
CH and atom ic and m olecu lar s p e c tr a o f hydrogen are s e e n , in a d d itio n to
th e helium l i n e s .

This in d ic a t e s a s t a t e o f stro n g decom p osition o f

th e o rg a n ic vapor and i s r e fe r r e d t o by S ch u ler as th e d e s tr u c tiv e s t a t e .
I f th e b ath tem perature i s now Increased somewhat, th e l i n e s p e c tr a b e g in
t o fa d e as do th e band s p e c tr a o f th e d ia to m ic m o le c u le s, and new band
s p e c tr a and co n tin u a are observed in th e v i s i b l e and u lt r a v i o l e t r e g io n s .
S e v e r a l new s p e c tr a , which are most c e r t a in ly due- t o polyatom ic fragm ents
d eriv ed from m ild d ecom p osition o f to lu e n e , occur in t h is in term ed ia te
s ta t e o

These s p e c ie s are d escrib ed in l a t e r paragraphs t o th e e x te n t

th a t th e e m itte r s o f th e s p e c tr a have been i d e n t i f i e d .

I f th e sample

vapor p r e ssu r e i s in crea sed s t i l l fu r th e r , but not t o th e e x te n t th a t
th e d isch a r g e i s co m p letely quenched o u t, an em issio n spectrum in th e
3000 A r e g io n i s observed, corresponding to t r a n s it io n s between th e
same e le c t r o n ic s t a t e s as in a b so rp tio n by th e benzene r in g .

The r a t io

o f c a r r ie r gas p a r t i a l p r e ssu r e t o sample p ressu re i s approxim ately l s l .
This low energy r e g io n i s c a lle d th e end s t a t e .
(2 )

Mechanism o f E x c ita tio n in th e Glow D isch a rg e.

To in te r p r e t

th e changes in th e s p e c tr a observed in th e experim ent j u s t d e sc r ib e d ,
one must co n sid er th e changes in e n e r g ie s o f th e v a rio u s s p e c ie s i n th e
glow d is c h a r g e .

S in c e both d ir e c t e le c tr o n impact e x c it a t io n of s p e c ie s

and in d i r e c t e x c i t a t i o n p r o c e sse s in v o lv in g e le c tr o n exchange between
atom s, m o lecu les and io n s presum ably o ccu r, i t i s n e c e ssa r y t o co n sid er
how th e e n e r g ie s and numbers o f a l l o f th e s e s p e c ie s are a lte r e d when
th e p a r t i a l p ressu re o f th e org a n ic sample i s in c r e a s e d .

17

In th e glow d isch a rg e in pure rare gas a t p r essu res i n th e range
o f a m illim e te r o f mercury as in d ic a te d e a r l i e r , th e p r in c ip a l em issio n
c o n s is te d o f th e arc spectrum o f th e ra re g a s, w ith spark l i n e s p resen t
o n ly a t low I n t e n s it y *

This in d ic a t e s th a t most o f th e rare gas io n s

have e n e r g ie s no h ig h er than th e f i r s t io n iz a t io n p o t e n t ia l f o r th a t
gas * Furtherm ore, s in c e c o l l i s i o n s o f an e le c t r o n w ith an u n excited
r a r e gas atom must be e l a s t i c i f th e e le c tr o n has energy below th e f i r s t
e x c it a t io n p o t e n t ia l o f th e rare g a s , in a h igh enough f i e l d grad ien t
th e e le c tr o n w i n co n tin u e t o be a c c e le r a te d u n t i l i t has enough energy
t o c o l l i d e i n e l a s t i c a l l y w ith a ra re gas atom.

The r e s u lt in g in c r e a se

i n p r o b a b ility o f i n e l a s t i c c o l l i s i o n when th e f i r s t e x c it a t io n p o t e n t ia l
i s reached r e s u lt s in c u t tin g o f f th e h igh energy end o f th e e le c t r o n
d is t r ib u t io n so t h a t , although th e r e are e le c t r o n s w ith e n e r g ie s even
h ig h er th a n th e f i r s t io n iz a t io n p o t e n t i a l , th ey are much few er in
number th a n th o se in th e range between th e f i r s t e x c it a t io n p o t e n t ia l
and f i r s t io n iz a t io n p o t e n t i a l.
and 2k .6 e .v ^ r e s p e c t iv e ly .

For helium th e s e p o t e n t ia ls are 2 1 .0 e . v .

These e n e r g ie s are s t i l l v e r y h igh compared

t o bond e n e r g ie s , which are o n ly about b e «v. i n organ ic m o le c u le s .
C on seq uently, th e in tr o d u c tio n o f sm a ll amounts o f sample vapor in to
th e helium d isch a rg e r e s u lt s in stro n g d ecom p osition o f th e organ ic
m o le c u le s, as noted by S c h u le r .
I f th e p a r t i a l p r essu r e of sample vapor i n th e d isch a rg e i s in ­
crea sed somewhat, th e c a r r ie r gas atom ic l i n e s b eg in t o fa d e , and l e s s
v i o l e n t d ecom p osition o f th e sample o c c u r s, r e s u lt in g in p olyatom ic
s p e c ie s w ith c o n sid e r a b ly few er d iatom ic fragm ents b ein g ob served .

18

T his r e s u lt s from th e g r e a t ly in crea sed op p ortu n ity fo r e le c tr o n s to
s u f f e r i n e l a s t i c c o l l i s i o n s w ith sample m olecu les ® Polyatom ic m olecu les
i n g en era l have many e x c ite d s t a t e s which l i e w e ll below th e f i r s t
e x c i t a t i o n p o t e n t ia l o f helium and th e oth er ra re g a s e s .

The e le c tr o n s

b e in g a c c e le r a te d i n th e e l e c t r i c f i e l d can be robbed o f t h e ir energy
by th e s e p olyatom ic m o lecu les b efo re th e energy becomes la r g e enough to
e x c i t e th e ra re g a s « This e f f e c t r e s u lt s in ra th er g rea t lim it a t io n o f
th e upper range o f e le c tr o n e n e r g ie s p r e se n t i n th e glow d isch a rg e i n
th e p resen ce o f sample v a p o r s .

Continued in c r e a s e o f th e p a r t ia l p ressu re

o f th e sample vapor r e s u lt s in th e end s t a t e , i n which c a r r ie r s p e c tr a l
l i n e s have co m p letely d isappeared and s p e c tr a o f undecomposed sample
m olecu les appear in many c a s e s D In t h is s it u a t io n , th e e le c t r o n e n e r g ie s
are la r g e ly d e lim ite d by th e sample vapor i t s e l f , s in c e p olyatom ic mole­
c u le s w ith t h e i r many a v a ila b le e x c ite d l e v e l s a few e le c tr o n v o l t s above
th e ground s t a t e are much more e f f e c t i v e i n undergoing i n e l a s t i c
c o l l i s i o n s w ith e le c t r o n s than are th e ra re g a s e s , w ith t h e i r sim ple
e x c ite d s t a t e s ly in g so h igh above th e ground s t a t e .
With S c h u le r ?s tec h n iq u e , th en , one has some c o n tr o l over th e range
o f e n e r g ie s o b ta in a b le in th e glow d isc h a r g e .

S in ce th e f i r s t e x c it a t io n

p o t e n t i a l and f i r s t io n iz a t io n p o t e n t ia l o f th e c a r r ie r gas determ ine
t o a g r ea t e x te n t th e upper range o f e le c t r o n e n e r g ie s in th e d isc h a r g e ,
t h i s l i m i t can be v a r ie d by v a ry in g th e c a r r ie r g a s .

The other para­

m eters a v a ila b le t o c o n tr o l e n e r g ie s have a lread y been m entioned— th a t
i s , th e r a t i o o f p a r t ia l p re ssu r e s o f c a r r ie r to sample gases and the
f i e l d t o p r e ssu re r a t i o in th e p o s it iv e column« S in ce under th e low

19

cu rren t c o n d itio n s which se r v e t o d e fin e th e ,!normal glow*'® where th e
p o t e n t i a l drop a c ro ss th e tu be remains co n sta n t w ith changes in current*
th e param eter o f e l e c t r i c f i e l d i s not v a r ia b le * and* f o r a given
system* th e r a t i o o f p a r t ia l p ressu re of c a r r ie r t o sample gas and the
t o t a l p re ssu re are th e param eters which may be c o n tr o lle d »
U sing th e s e param eters as a b a s is o f energy con trol* Sch iller has
endeavored to e s t a b lis h a g en era l f i e l d o f e le c t r o n ic e m issio n sp e ctro sco p y
o f p olyatom ic m olecu les* to g e th e r w ith th e p olyatom ic fragment m olecu les
and io n s d eriv ed from m ild d ecom position of sample vapors <> S chuler has
developed s e v e r a l tech n iq u es f o r is o l a t i n g s p e c tr a and id e n t if y in g t h e ir
e m itte r s <.
(3 )

R efinem ents o f th e Technique Which Aid i n I d e n t if y in g S p e c tr a l

E m itters o S ch u ler (1 ) has t r ie d a la r g e number o f c a r r ie r gases in c lu d ­
in g helium* neon* argon* krypton* hydrogen* n itrogen * sodium* mercury*
cycloh exan e and benzene „ The organic c a r r ie r s were used in a system
whereby th e org a n ic m olecu les were f i r s t e x c ite d by helium* and then
th e s e e x c ite d m olecu les were used to carry th e d isch a rg e to th e sample
vaporo

A v er y w ide range o f f i r s t e x c it a t io n and f i r s t io n iz a t io n

p o t e n t ia ls was th u s c o v e r e d --! <>e o* U«7 e°v<, and 9-2 e 0v 0* r e s p e c tiv e ly *
f o r benzene and 21 e ov 0 and 2U<>6 eoVc* r e s p e c tiv e ly * f o r helium..
I t was found th a t helium i t s e l f could be used a d eq u ately f o r e x c it a t io n
o f low energy s p e c tr a under c o n d itio n s o f th e end s t a t e 0

The u se o f

v a r io u s c a r r ie r gases was* however* a v ery u s e f u l tech n iq u e in h e lp in g
t o i d e n t i f y th e em itte r o f a p a r t ic u la r spectrum* s in c e s p e c ie s req u irin g
e le c t r o n e n e r g ie s above th e io n iz a t io n p o t e n t ia l o f th e c a r r ie r gas

20

were n ot e x c ite d by th a t p a r t ic u la r c a r r ie r g a s, but would be by one
w ith a h ig h er io n iz a t io n p o t e n t i a l .

This h elp s s e t a low er l i m i t on

th e energy req u ired t o e x c it e t h i s s p e c ie s , or t o form i t from th e sample
m o le c u le «
G lues t o th e i d e n t i t y o f s p e c t r a l e m itte r s were a ls o obtained from
th e s t r u c t u r a l u n its in th e v a rio u s saiqple vapors which could g iv e r i s e
t o th e spectrumo

Of cou rse comparison o f th e em issio n s p e c tr a w ith

em issio n s p e c tr a o b tain ed in c o n v en tio n a l flu o r e s c e n c e s tu d ie s and —
a b so rp tio n s p e c tr a o f s a p o r s in many c a ses gave h in ts t o th e i d e n t it y
o f th e em ittero

In many c a s e s , f in e s tr u c tu r e could be r e so lv e d and

deuterium s u b s t it u t io n em ployed«,
(U) New S p e c tr a Observed Using th e S ch u ler Technique.

U sing th e se

tec h n iq u e s S ch u le r and co-w orkers have observed s p e c tr a d escrib ed below
and deduced a number o f th e e m itters r e s p o n sib le f o r th e s p e c tr a .
Benzene d e r iv a t iv e s em it a spectrum in th e near u l t r a v i o l e t r e g io n
a r is in g from th e e x c it a t io n o f th e e le c tr o n s o f th e benzene r in g .
C erta in s u b s tit u e n ts o f low io n iz a t io n p o t e n t ia l i n h i b it t h is e m issio n ( 8 ) .
A d i f f u s e green spectrum from benzene d e r iv a t iv e s in th e r e g io n hb56 A
t o 59^0 A has been a ttr ib u te d t o th e b e n z y l r a d ic a l.

A spectrum c o n s is t ­

in g o f two d if f u s e groups in th e reg io n s U75>Q“U9GQ A and 500Q-5U00 A
i s ob serv ed , a r is in g from b en zenoid hydrocarbons, but t h e e m itte r remains
unknown * A continuum observed in th e r e g io n 3 liOO-UUGO A has been
t e n t a t i v e l y a ssig n e d t o th e dehydrobenzene m olecule CqH4 .

S tron ger

d ecom p osition o f arom atic hydrocarbons, or p o ly m er iz a tio n o f o l e f i n i c
or a c e t y le n ic hydrocarbons, r e s u lt s in th e d ia c e ty le n e p o s it iv e io n

21

w hich em its bands in th e r e g io n I+763 A t o 6500 A (1 0 ) *

The d ia c e ty le n e

p o s i t i v e io n spectrum was f i r s t observed by S ch u ler and a ssig n ed t o th e
n e u t r a l m olecu le •

L ater h igh d is p e r s io n work by Calloman (11) r e s u lte d

in r e c o g n itio n o f th e d ia c e ty le n e p o s it iv e io n as th e e m itte r .
B lu e , str u c tu r e d , continuous em issio n by benzaldehyde and sub­
s t i t u t e d benzaldehydes has been observed by S ch u ler ( 1 2 ) .

The em issio n

was v e r y in te n s e and d e t e c ta b le a t benzaldehyde co n cen tra tio n s o f one
p a rt per m illio n .

S c h u le r , Gollnow and W oeldike (13) observed th e

con tin u ou s b lu e em issio n o f a ceton e and acetop hen one.
S ch u ler and W oeldike (U4) rep ort t e n , v i o l e t degraded, em issio n
bands in th e r e g io n 5315 A t o 6162 A o r ig in a tin g from th e quinone mole­
c u le .

The r o t a t io n a l f in e s tr u c tu r e in th e s e bands was smeared out by

adm ixture o f h y d r o x y l-c o n ta in in g s p e c ie s in th e d is c h a r g e .

Hydrogen

bonding between th e h y d r o x y lic hydrogen and th e q u in o id a l oxygen i s
presumed r e s p o n s ib le f o r t h i s e f f e c t .
New form aldehyde bands a t 351+5 A and 31+06 A degraded t o th e red
were observed in th e glow d isch a rg e spectrum o f form aldehyde b y S ch u ler (15).*
S ch u ler and Reinebeck (1 6 ) rep orted em issio n in th e 31QG A r e g io n
a r is in g from m olecu lar n ap h th alen e.
o f s p e c ie s d eriv ed from n a p h th a len e.

They a ls o observed fou r new sp e c tr a
One o f th e se s p e c ie s i s presumed

t o be l , 2 , 3 ,U“tetra h y d ro n a p h th alen e, and i t s d if f u s e spectrum occurs in
th e reg io n 1+70Q A t o 5100 A.

The o th er sp e c tr a are presumed t o b elo n g

t o sm a lle r fragm ents o f th e m o le c u le .

These s p e c tr a are;

5180-6000 A

( d i f f u s e ) 5900 A ( d if f u s e bands occu rrin g a t h ig h er vapor p r e s s u r e s ),
39&Q A, 1+21*0 A, 1+1+80 A ( d if f u s e b a n d s).

22

S ch u ler and Reinebeck ( 9 ) rep ort th a t indene and hydrindene in th e
glow d isch a rg e g iv e r i s e t o a spectrum in th e r e g io n Jl630~5050 A which
i s s im ila r t o th e spectrum a ttr ib u te d t o l,2 ,3 ,li.-tetra h y d r o n a p h th a len e
above.
W ater su b jected t o th e glow d isch arge by S ch u ler (1 7 ) produces seven
red degraded bands i n th e r e g io n 1j.2G0-5U80 A, shown t o b e em itted by
th e n e g a t iv e ly charged h ydroxyl r a d ic a l.

Bands between 5635 A and 5670 A

have been observed by S ch u ler (1 8 ) in th e glow d isch a rg e o f ammonia
v a p o r.

The ammonia m olecule i s presumed t o be th e e m itte r .

MLlazzo ( 1 9 ) / u sin g a Schuler tu b e , has observed e m issio n o f th e
N -m ethyl p y r r o le m o le c u le .

The spectrum c o n s is t s o f f if t y - t w o f a in t bands

betw een 2878 A and 2 J4.OO A.
( 5 ) L im ita tio n s o f th e Technique.

D e sp ite th e ap p aren tly la r g e

number o f s p e c tr a rep o rted , th e method h a s, u n fo r tu n a te ly , not proven
t o be as g en era l as was at f i r s t hoped.

The sp e ctra o f n e u tr a l m olecu les

observed w ith o u t fra g m en ta tio n , in a l l c a ses where i t could be a s c e r ta in e d ,
a ro se from t r a n s it io n s between th e f i r s t s in g l e t e le c t r o n ic e x c ite d
s t a t e o f th e m olecu le and th e ground e le c t r o n ic s t a t e o f th e m o le cu le .
T r a n s itio n s betw een h ig h er e x c ite d s t a t e s , and from th e second e x c ite d
s t a t e t o th e ground s t a t e , were n ot observed even f o r a number o f mole­
c u le s h aving stro n g t r a n s i t io n p r o b a b ilit ie s f o r th e corresponding
a b so r p tio n s.

I n s te a d , fragm en tation would occur*

Thus, ra th er than

o b ta in in g e x te n s iv e t r a n s it io n s among a la r g e number o f e x c ite d s t a t e s
o f n e u t r a l m o le c u le s, in many ca ses em issio n by p olyatom ic f r e e r a d ic a ls
and io n s i s ob served .

This in i t s e l f , however, has in t e r e s t in g

23

r a m ific a tio n s f o r th e c h em ist.

The s im ila r it y o f e le c t r o n impact

e x c i t a t i o n to r a d ia tio n ch em ical p r o c e sse s induced by oth er io n iz in g
r a d ia tio n s w i l l be d isc u sse d in a la t e r s e c t io n .
c . R e s u lts from Other Techniques o f Glow D ischarge E x c ita tio n o f
M olecular E m ission S p ectra
R adiofrequency 5 e le c t r o d e le s s e x c it a t io n o f flo w in g vapors seems
to g iv e s p e c tr a v e r y s im ila r t o th o se r e s u lt in g from S c h u le r 's method
e x c ep t th e r e appear t o be few er ways t o vary th e energy a t t a in e d .

The

e le c t r o d e le s s glow d isch a rg e has been w id e ly u sed , but few compounds
have been stu d ie d beyond th o se reported by S ch tile r .
Vacher and l o r t i e (2 0 ) rep o rt having separated th r e e energy ranges
in a ra d io freq u en cy d isch a rg e o f flo w in g organ ic vapors by r e g u la tin g
th e power in p u t and th e vapor p ressu re o f th e sam ple.

In th e se energy

ra n g e s, which correspond to S c h u le r 's d e s tr u c tiv e s t a t e , in term ed ia te
s t a t e , and end s t a t e , were observed many o f th e sp e c tr a o f s p e c ie s
d er iv ed from arom atic compounds«, In a d d itio n , th e s e authors rep o rt a
band a t hk9$ A observed in a p ip e r id in e d isch a rg e and a new band in th e
b e n z y l r a d ic a l spectrum a t 5963 A.
Much o f th e l a t e r work has been concerned w ith h ig h er r e s o lu t io n
o f em issio n sp e c tr a in th e glow d isch argeo
benzene and to lu e n e em issio n e x te n siv e ly ..

Leach (21) has stu d ied
F au ris (22) has stu d ied th e

aceton e continuum c l o s e l y , f in d in g th a t b e s id e s th e maximum near U500 A
observed by S c h u le r , th e r e i s a ls o a sm all maximum a t 2900 A correspond­
in g t o th e a b so rp tio n peak in th a t r e g io n .

Robinson ( 23) has made h igh

r e s o lu t io n s tu d ie s o f th e benzaldehyde and acetophenone b lu e eontinua

2h

p r e v io u s ly observed by S c h u le r .

The con tin ua e x h ib ite d banded s tr u c tu r e .

Robinson employed a rad iofreq u en cy e x c i t e r , and d is s o lv e d th e samples
in to lu e n e or b en zen e, th en allow ed th e s o lu t io n t o v a p o rize and flo w
r a p id ly through th e e le c t r o d e le s s e x c i t e r .

The to lu e n e and benzene em it

in th e u l t r a v i o l e t , b u t do n ot in t e r f e r e w ith th e v i s i b l e con tin u a o f
th e m o lecu les s tu d ie d .

The to lu en e or benzene a c ts som ething l i k e a

c a r r ie r g a s, a llo w in g u se o f sm a ller samples than would be needed f o r
th e pure m a t e r ia ls .

Robinson ( 2U) a ls o rep o rts a stru ctu red continuum

w ith a maximum about U2GG A f o r a ceta ld e h y d e .
observed by R egnier ( 25) *

T his spectrum has a ls o been

Gaydon (2 6 ) has observed th e em issio n o f

m olecu lar g ly o x a l which c o n s is te d o f th ir ty -o n e bands in th e reg io n
UUOU A t o 5729 A.

S t y le and Ward ( 27) e x c ite d th e spectrum o f HCOOe in

form ic a cid u sin g a rad iofreq u en cy d isc h a r g e .

Dyne ( 28) has observed

f o r t y new bands e x c ite d in a c e ty le n e and b e lie v e d them t o be due t o th e
a c e ty le n e m o le cu le .

The bands l i e between 2399 A and 2920 A and are

superimposed on a continuum .
Suryanar ayana, Rao, and Rao (29) have analyzed th e u l t r a v io le t
em issio n sp e c tr a o f o rth o , m eta, and para flu o r o to lu e n e s observed in
an o so n iz e r typ e d isc h a r g e .

The ortho compound em itted seven f a in t

bands between 2661 A and 2835 A.

The meta isom er em itted tw en ty -sev en

d o u b let bands betw een 2?60 A and 2951 A.

T h irty-tw o a lte r n a tin g d ou b let

and s i n g l e t bands were observed between 2?03 A and 310U A fo r th e para
compound.
Some new s p e c tr a o f sm a ll m olecu les have r e c e n t ly been observed in
th e glow d isc h a r g e .

Venkateswarlu (3 0 ) has observed an e x te n s iv e system

25

o f bands In th e r e g io n betw een 2300 A and 1±8QQ A,

The e m itte r i s CF2 .

Andrew and Barrow (3 1 ) rep orted f i v e c lo s e sequences ly in g i n th e reg io n
1970 A t o 2210 A havin g red-degraded bands to be em ission fcy th e CF
m oleculeo

A second u l t r a v i o l e t system ch a ra cterized by a d o u b le, double­

headed band degraded t o th e v i o l e t a t 22l|0 A a ls o was observed f o r CF.
Upon e x c it in g CBr4 v ap or, Durie and I r e d a le ( 32) have found d if f u s e
bands a t 3530 A* 3336 A, 3120 A, 2909 A, 2755 A, and 2658 A which th e y
p r o v is io n a lly a ssig n ed t o CBr*
Callomon (3 3 ) and Laird and Barrow (3U) have stu d ied th e h ollow
cathode glow d isch a rg e o f CS2 vap or, a ssig n in g th e observed spectrum to

B e n o ist (3 5 ) has observed th ree new bands in th e e le c t r o d e le s s d i s ­
charge in w ater vapor*

The band heads are 25U1* A, 2U65 A, and 237U A

and a ssig n ed t o OH*
E l K halafaw i and J o h a n n in -G illes (3 6 ) have stu d ied carbon t e t r a ­
c h lo r id e in th e vacuum u l t r a v i o l e t r e g io n and observed o n ly atom ic
c h lo r in e and carbon lin e s *
Ambrush ( 37) has p u b lish ed a b r i e f review o f em issio n sp e c tr a o f
organ ic compounds in gaseous d isch a rg es through 1 9 5 3 *
2« S tu d ie s of R ea ctio n Mechanisms in 't h e Glow D ischarge
a* G eneral
I n tr y in g to u n ra v el mechanisms o f product form ation i n th e glow
d is c h a r g e , a few system s have been su b jected to product a n a ly s is o f
e it h e r o f two s o r t s —-chem ical a n a ly s is o f products formed by th e d i s ­
charge or s tu d ie s o f th e sp e c tr a em itted or absorbed w ith in th e d isc h a r g e .

26

The s p e c tr o s c o p ic method s u f f e r s th e lim it a t io n th a t th e r e w i l l a ls o be
s p e c ie s formed which e it h e r do not em it in th e w avelength r e g io n a v a il­
a b le f o r stu d y , or are formed in t h e ir ground e le c t r o n ic s t a t e s and
th e r e b y do n o t em it, u n le ss e x c ite d su b seq u en tly in a secondary p r o c e s s .
With a b so rp tio n s p e c tr a , t h e s e d i f f i c u l t i e s would n o t a r is e , but
a b so r p tio n s p e c tr a o f u n sta b le in ter m ed ia tes in th e vapor are g e n e r a lly
much more d i f f i c u l t t o observe ex p erim en ta lly than em issio n s p e c tr a , and
co n seq u e n tly t h i s method o f a n a ly s is has not y e t been w id e ly a p p lied t o
th e problemo

Inform ation from such s tu d ie s as t h e s e , o f co u rse, can have

a p p lic a tio n in sy n th e se s o f many compounds o A su rvey o f th e se ty p e s of
s tu d ie s f o llo w s *
bo Chemical A n a ly sis o f Products
S ch u ler and Degenhart ( 38) have found d ib e n z y l, benzene and a th ir d
lo w - b o ilin g , non-arom atic su b stan ce t o be formed in th e glow d isch a rg e
d ecom p osition o f to lu e n e .

Benzene i s shown t o produce d ip h en y l.

Ammonia

i s found t o g iv e hydrazine a t th e r a te o f t h ir t e e n grams per k ilo w a tt
hour (3 9 ) o This i s more e f f i c i e n t than any oth er e l e c t r i c a l p ro cess
d ev ised f o r making hydrazine from ammonia.
K roep elin (UO) has found th a t benzene in th e S ch u ler-ty p e d isch a rg e
produces methane, e th y le n e , a c e ty le n e , p rop ylen e, propyne, d ia c e t y le n e ,
t o lu e n e , and b ip h e n y l.

Toluene produces a l l o f th e above excep t b ip h e n y l,

and moreover produces diphenylm ethane, b u ty le n e , e t h y l benzene, and
phenanthrene•

2?

Holzman and Morris (1+1) have used a glow d isch a rg e e x c it e d by
microwave t o produce B 2G14 from BC130

The em issio n spectrum o f BG1 was

observed in th e d is c h a r g e „
c . S p e c tr o sc o p ic E m ission S tu d ies
R e la t iv e ly l i t t l e work in product chem ical a n a ly s is l i k e th e above
has been done <> More numerous s tu d ie s o rien ted towards s p e c t r a l typ e
i n v e s t ig a t io n have been made

o

A number of th e s e are summarized b elo w .

M ilazzo (U2) has stu d ie d th e d ecom p osition p a tte r n s o f five-m embered
h e t e r o c y c lic r in g compounds u sin g a Schuler-“type d isc h a r g e .
furan* p y r r o le , N-m ethyl p yrrole* thiophene and selen op h en e.

He stu d ied
He measured

r e l a t i v e abundances o f H2* C2* GH* CO* C4 H2* , OH* NH* ON* CS* GSe* 0 2*
N2* S 2* S e 2 w ith helium and in some c a ses neon and argon c a r r ie r g a s e s .
He has p o stu la te d some d ecom p osition mechanisms from h is f in d in g s .
V asil" ev (1*3) has made a k in e t ic stu d y o f th e form ation o f NO from
N2 and 0 2* and o f th e d ecom p osition o f methane in th e e l e c t r i c d isc h a r g e .
He found th a t both are f i r s t order w ith r e s p e c t t o co n ta ct tim e w ith th e
d isch arge* in c o n tr a st t o th e second order therm al p r o c e s s e s .

Burton

and Manion (UU) u sin g deuterium s u b s t it u t io n i n stu d yin g th e decom position
o f methane in an e l e c t r i c a l d isch a rg e have concluded th a t e x c ite d s t a t e s
o f methane p la y l i t t l e p a rt in th e d ecom p osition to y i e l d a cety len e*
hydrogen and carbon 0 Methyl r a d ic a l i s presumed to be t h e p r in c ip a l
s p e c ie s excited *an d th e CH2 formed therefrom i s th e s p e c ie s p resen t in
im portant c o n c e n tr a tio n .

K olyubin (1+5) has observed e m issio n from GH*

H2* H* GO* QH* CII and Cl in an e le c t r o d e le s s d isch a rg e in n on -flow in g
vapors o f methanol* ethanol* b u ta n o l and isoam yl a lc o h o l.

28

In th e s ta tio n a r y vapor* i n t e n s i t y r a t io s o.f l i n e s depend on th e p ressu re <>
In a flo w in g system th e y s t a t e th a t th ey have shown th a t GH^ i s a product
o f a primary r e a c tio n such ass
e

CH3 OH ———s* 0HW ♦ GH3

e~

ard t h a t GO* H* and 0 are p rod ucts of secondary r e a c tio n s * Kokado* Mori
and Tanaka (U6 ) have stu d ie d th e spectrum o f to lu e n e in th e glow d isch a rg e
as a fu n c tio n o f p re ssu re (an d ?of cours©; e le c tr o n energy) * They found
t h a t a t p re ssu r e s g r e a te r than 10 mra* where th e e le c tr o n en e r g ie s are
estim a ted as < h S ©°Vo* th e em ission i s due t o th e to lu e n e m olecule
t r a n s it io n o

In th e p ressu re range o f Go^-lO mm where e le c tr o n

e n e r g ie s are hS~& e . v , th e

t r a n s it io n o f th e benzene m olecule

was observed o At p ressu re s between 0*1 and 0*5 mm,,the e le c tr o n e n e r g ie s
were estim a ted t o be 6 -8 *5 ©^v^and th e spectrum o f b e n z y l r a d ic a l was
observedo

At p r e ssu r e s below G d mmUJ C2 and other products o f decompo­

s i t i o n o f th e r in g were o b served 0

The e le c tr o n e n e r g ie s were estim ated

as b e in g above 8 <>5 a.Vo then 0
R ossik h in and Tsykora ( h i ) on th e b a s is o f t h e ir s p e c tr a l stu dy o f
h ig h freq u en cy d isch a rg e in system s c o n ta in in g C02, CC14 * and t h e ir mix­
tu r e s w ith hydrogen and nitrogen* have proposed th a t th e form ation o f C2
r e q u ir e s f r e e carbon atoms as does th e form ation of GNo

The GH bands

are observed o n ly from m ixtures c o n ta in in g hydrogen* th e mechanism b ein g
probably th e com bination o f f r e e carbon and hydrogen atom s»
Jan in (I48) has stu d ied th e r e la t iv e band i n t e n s i t i e s in th e glow
d isc h a r g e p o s i t i v e column in o n e-to -o n e molar r a t io m ixtures o f methane

29

and ammoniao

The GH r a d ic a l i s presumed "to p la y an e s s e n t i a l r o le in

th e form ation o f HCN^ s in c e th e r e la t iv e i n t e n s i t y o f th e CH e m issio n
in c r e a s e s p a r a l l e l t o th e form ation o f GN and HCN as th e cu rren t i n th e
d isc h a r g e i s in cr e a se d <>
Norman (U9) has a p p lied th e tech n iq u e o f s p e c tr a l o b serv a tio n o f
d ecom p osition p a tte r n s in th e glow d isch arge to chem ical a n a ly s is o f
polymer f ib e r s <> The f ib e r sam ples were p laced upon e le c tr o d e s between
which was stru ck a glow d isch a rg ee

By ob servin g th e d ia to m ic and atom ic

s p e c ie s which e m itte d , he succeeded in d if f e r e n t ia t in g a la r g e number o f
polym er ty p e s on th e b a s is o f r e l a t i v e i n t e n s i t i e s o f th e many fragm ents
a p p ea rin g »
3 o Other S ou rces o f E le c tr o n Impact E x c ita tio n
a* I o n iz in g R a d ia tio n
B e sid e s e x c it a t io n o f s p e c ie s in th e glow d isc h a r g e , e le c t r o n impact
i s a ls o an im portant means o f e x c it a t io n in two oth er ty p e s o f stu d y .
In r a d ia tio n ch em istry in v o lv in g high energy p a r t ic le s , e le c tr o n s e je c te d
in prim ary p r o c e sse s in v o lv in g th e io n is in g p a r t ic le s or gamma rays are
r e s p o n s ib le f o r a la r g e p a rt o f th e chem istry occu rrin g subsequent t o
th e prim ary p r o c e ss * These secondary e le c tr o n s proceed through th e
sample medium, and t h e ir im pact w ith sample m olecules may be expected
t o produce chem ical r e s u lt s analogous to e le c tr o n impact e x c it a t io n in
a glow d is c h a r g e 0

30

b= The Mass Spectrograph
In th e mass sp ectro g ra p h , m olecu les are bombarded w ith e le c tr o n s !
th e r e s u lt in g p o s i t i v e io n s o f th e sample m olecule or fragm ents
th erefrom are th en d e te c te d accord in g t o t h e ir m ass-to-ch arge r a t i o .
From th e mass sp ectro g ra p h , voluminous in form ation regard in g breakdown
p a tte r n s o f m olecu les i s becoming a v a ila b le .
As an example o f t h is typ e o f in form ation , co n sid er th e mass spectrum
o f is o p r o p y l a lc o h o l, l i s t e d in th e American Petroleum I n s t it u t e C atalog
o f Mass S p e c tr a l Data (5G) <> The most abundant io n in th e iso p ro p y l
a lc o h o l spectrum has mass US and corresponds to S S p ercen t o f a l l th e
io n s form ed.

I t s form ation may be presumed t o be as follow s^

(GH3 ) 2CH0H * e

—■

CHgCKOK' + 0\i3 + 2 e“

Friedman and Turkevich (5 1 ) have shown from deuterium s u b s t it u t io n
s t u d ie s th a t th e hydrogen on th e oxygen and th e secondary hydrogen atom
are r a r e ly l o s t i n th e p ro cess o f form ation of th e io n o f mass US»
T heir r e s u lt s are c o n s is te n t w ith th e gen eral mechanism fo r a lc o h o ls
proposed by Cummings and Bleakney (52), in which an e le c tr o n i s removed
from one o f th e non-bonding oxygen o r b i t a l s .

The r e s u lt in g p o s it iv e

oxygen atom se ek s t o compensate f o r i t s e le c tr o n d e f ic ie n c y by form ing
an a d d itio n a l v a le n c e bond w ith th e carbon atom to which i t i s alrea d y
bound.

This can happen o n ly i f one of th e oth er s u b s titu e n ts o f t h is

carbon atom i s removed.

G en era lly , in a lc o h o ls th e most w eakly bonded

s u b s tit u e n t w i l l be l o s t form ing th e most abundant io n .

In th e ca se o f

is o p r o p y l a lc o h o l, th e m ethyl s u b s titu e n t i s l o s t form ing th e io n o f mass U S •

31

F r o st and McDowell ( 53) have shown* u sin g io n iz a t io n by e le c tr o n s
in th e mass spectrograph w ith p u lse techniques* th a t e x c ite d s t a t e s of
io n s o f m ethyl io d id e and m ethyl bromide e x i s t th e r e *
S in c e no c h a r a c t e r is t ic em issio n s p e c tr a have been reported in th e
glow d isc h a r g e o f a lip h a t ic a lc o h o ls or a lk y l h a lid e s* and mass s p e c t r a l
d a ta show t h a t la r g e fragm ents are formed in e le c tr o n impact and are
s t a b le enough t o tr a v e r s e th e mass spectrograph and be d etected * i t was
d ecid ed t o ap p ly a tech n iq u e which was developed in t h is lab oratory* and
was s im ila r to S c h u le r : s method o f e x c ita tio n * to some o f th e sa tu ra ted
o rgan ic compounds t o s e e whether such sp e c tr a e x is t.,
Bo Em ission S p ectra in a Flow System
With a C arrier Gas
I* E xperim ental
a , G eneral D e s c r ip tio n of E xperim ental Approach
E a rly e f f o r t s a t o b ta in in g m olecular em ission s p e c tr a had been
plagued by e x c e s s iv e chem ical breakdown in th e d isch a rg e tube.,

S chu ler

dem onstrated th e p o s s i b i l i t y of c o n tr o llin g energy and r e s t r i c t i n g
breakdown by u se o f an in e r t c a r r ie r gas in a s p e c ia lly designed and
e la b o r a te d isch a rg e tube.,
In t h i s in v e s tig a tio n * a sim p ler c a r r ie r gas tech n iq u e was employed*
in which th e pure c a r r ie r was fed through an e le c t r o d e le s s d isch arge tube
p a ssin g through th e e x c it e r c o il* and sample vapor was introduced in to
th e c a r r ie r stream w e l l downstream from th e r e g io n o f e x c it a t io n .
The ca r rie r-sa m p le stream th en passed through th e o b serv a tio n tube* a
lon g c a p illa r y tu be w ith a waxed-on quartz window.

In a la t e r

32

m o d ific a tio n * no c a r r ie r was used but th e e x c it e r c o i l was lo c a te d
downstream from th e o b se rv a tio n tube* so th a t breakdown products were
swept out o f th e r e g io n o f s p e c t r a l ob servation..

In both m o d ifica tio n s*

o b se r v a tio n and rap id scan nin g o f th e spectrum were f a c i l i t a t e d by th e
u se o f a reco rd in g p h o t o e le c t r ic spectrophotom eter..
I t was o r i g i n a l l y hoped th a t a stu d y could be made o f s p e c tr a
em itted by some o f th e la r g e r fragm ents known from mass sp e c tr o s c o p ic
d a ta t o be o b tain ed in e le c t r o n bombardment o f a lc o h o ls and p o s s ib ly
even alkanes* e x c ite d u sin g argon as th e c a r r ie r gas*

The ch o ice o f

argon was based on i t s low er io n iz a t io n p o t e n t ia l ( 1 5 .8 v o l t s ) and
m e ta sta b le s t a t e ( 11*5 v o l t s ) as compared t o helium ( 2h *6 and 2 1 v o lts *
r e s p e c t iv e ly ) * I t was hoped th a t th e m ild er e x c it a t io n w ith argon
would l i m i t breakdown and p rovid e a s it u a t io n fa v o r a b le f o r e x c it in g
s t a t e s o f th e m olecu les or la r g e m olecu lar fragm en ts.

Towards t h is end*

th e spectrum o f argon i t s e l f was f i r s t observed w ith th e apparatus*
and th en s p e c tr a were observed w ith th e variou s organic vapors introduced
I n to th e argon stream*
b* Reagents
(l)

Argon*

Matheson Company commercial grade argon (99*998 p ercen t

s p e c if ie d minimum p u r ity ) from a s iz e 2 c y lin d e r was p u r ifie d in th e
fo llo w in g way.

The argon was passed through a 0*5 mnui. d. by 10 cm. lon g

f lo w -'r e s tr ic t in g c a p illa r y and th en through a t r a in c o n s is t in g of- f i f t e e n
in ch es o f anhydrous magnesium p e r c h lo r a te in a tube o f one and o n o -h a lf
in ch es diam eter* w ith two in ch es o f c lo s e ly packed Pyrax w ool r e ta in in g

33

th e d r y in g agent .

The gas next passed through a sm a ll liq u id a ir tra p

and th en through a 15 mm. i . d. Vycor tube c o n ta in in g tw e n ty -s ix in ch es
(113 go} o f calcium m etal tu r n in g s , ground to 10-20 mesh.
was k ep t in p la c e in th e tube by s t e e l w ool p lu g s .

The calcium

Both o f th e s e m etals

were washed th o ro u g h ly in petroleum eth er and d ried in vacuo two days
a t 50° Go

The Vycor tube passed through a o n e -fo o t lo n g tube fu rn a ce,

th e c e n te r o f which was h eld a t 650 ° G. d uring th e p u r if ic a t io n p r o c e s s .
The gas was then b led out through a vacuum pump, or passed in to a tw e lv e l i t e r sto r a g e f l a s k .

B efore each batch o f gas was p u r if ie d , th e Vycor

tube was advanced fo u r in ch es in th e d ir e c t io n o f th e gas flow t o b rin g
fr e s h m etal in to th e red h o t area in th e fu r n a c e .

The system was evacu­

ated a t th e b eg in n in g o f th e p ro cess and flu sh e d w ith argon, then
brought up t o tem p eratu re.
hour was u se d .

An argon flow r a te o f about s i x l i t e r s per

The system was purged w ith argon u n t i l th e second

p o s i t i v e bands o f N2 a t

h0%9 A and

3998 A could n ot be observed

w ith a v i s u a l sp e ctro sco p e in a glow d isch a rg e e x c ite d in th e e f f lu e n t
argon by a T esla c o i l .

The sto r a g e f la s k was th en rin se d w ith argon

th r e e tim es by f i l l i n g to about 100 mm. p ressu re and ev a cu a tin g , and
th e gas was c o l l e c t e d .

The p u r ity o f th e gas was f i n a l l y checked more

s e n s i t i v e l y in th e d isch a rg e system d escrib ed in the fo llo w in g s e c t io n
on ex p erim en tal p ro ced u re.
( 2 ) H elium .

Matheson Company commercial grade helium ( 99- 99 p ercen t

s p e c if ie d minimum p u r ity ) was used w ith ou t p u r if ic a t io n .
( 3 ) Organic Sam ples.

Organic sam p les, except in one in s ta n c e , were

A. C. S. rea g en t grade chem icals p u r ifie d by sim p le vacuum d i s t i l l a t i o n ,

3k

r e t a in in g th e ce n te r f r a c t io n f o r u se in th e ex p erim en ts.

The d ic y c lo -

p ro p y l k eton e sample -was k in d ly fu rn ish ed by Mr, Romeo C ip r ia n i,
Co Apparatus
(1 )

D isch a rg e S ystem ,

As has b een mentioned e a r l i e r , many workers

have used an e l e c t r o d e l e s s , h igh freq u en cy means o f e x c it a t io n o f th e
glow d is c h a r g e .

The r e s u lt in g s p e c tr a are s im ila r to th o se obtained

by S c h u le r ^ low freq u en cy d isc h a r g e , but s u f f e r from th e d isad van tage
t h a t th e en ergy range o f e x c it a t io n cannot be lim ite d by th e c a r r ie r
gas io n iz a t io n p o t e n t ia l and th e r a t i o o f p a r t ia l p ressu res o f th e
c a r r ie r gas and sample v a p o r.

The e le c t r o d e le s s d isch a rg e i s v e r y con­

v e n ie n t e x p e r im e n ta lly , however, s in c e no m e ta l- to - g la s s s e a ls are
n e c e s sa r y , and th e apparatus i s somewhat more f l e x i b l e b ecau se th e p o in t
o f e x c it a t io n can be moved r e a d ily .

In attem p tin g to observe em issio n

s p e c tr a o f a lip h a t ic a lc o h o l m o le c u le s, or p olyatom ic fragm ents d erived
from them in th e glow d is c h a r g e , i t was found th a t th e c a r r ie r gas te c h ­
nique seemed t o work w ith a high freq u en cy e x c it e r much th e same as in
'S ch u lers-exp erim en ts w ith low freq u en cy a lte r n a tin g cu rren t.
The apparatus used i s d ep icte d s c h e m a tic a lly in F igure 2 .

A flo w

system was u sed, whereby c a r r ie r gas from th e 1 2 - l i t e r f la s k , A, con tin u ­
o u sly flow ed in to th e e x c it e r tu b e , F, and o b serv a tio n sp a ce, 0 , and was
exhausted through th e vacuum pump.

The e x c it e r was a sm a ll T esla c o i l ,

which i s com m ercially a v a ila b le as a la b o r a to r y lea k t e s t e r .

The c o i l

i s a sou rce o f 3~U M e . p . s . , UO-^Q k i l o v o l t current in 120 c . p . s .
p u is e s .

For continuous o p eration th e c o i l was cooled by a sm all fa n

35

o p era tin g c lo s e to th e case,.

The T esla c o i l was coupled t o th e d i s ­

charge system by means o f a s t r i p o f aluminum f o i l one inch w id e, A l,
wrapped around th e e x c it e r tu b e , F, 20-25 cm. from th e bend in F.
The p o in ted probe was removed from th e lea k t e s t e r and th e ends of th e
aluminum f o i l in s e r te d in th e end o f th e case t o make co n ta ct w ith th e
h ig h v o lt a g e secondary o f th e c o i l .
The con n ectin g tu b in g in th e system was 8 mm. o . d . P yrex.

The

e x c it e r tu b e , F, was 10 ram. o . d . , th e o b se rv a tio n space was & 30 cm.
le n g th o f 3 mm. i . d . Pyrex c a p illa r y tu b in g .

The f lo w - lim it in g c a p illa r y ,

G, was 13 cm. o f 0 .5 mm. i . d . c a p illa r y tu b in g .
o b liq u e b o r e .

A ll stop cock s were J4 mm.,

Those la b e le d S I and S2 had been notched s l i g h t l y on th e

p lu g t o a llo w slow leak age i f d e s ir e d .
used were s i z e 1 2 /3 0 standard ta p e r .

C on ical grou n d -glass j o in t s
B a ll and so c k e t j o in t s were in t e r ­

ch an geab le, 1 8 /7 , s p h e r ic a lly ground.

J o in ts and stop cock s were lu b r i­

cated w ith Dow-Corning s i l i c o n e , high vacuum g r e a s e .

The tr a p , T l, bathed

in liq u id a i r , is o la t e d th e open-end p ressu re r e l i e f manometer, M, from
th e sy stem , s in c e mercury, having a low energy m etastab le s t a t e , would
have been an u n d e sir a b le im p u rity.

The liq u id a ir cooled tr a p , T2,

c o lle c t e d th e sample vapor which was b led in to th e o b serv a tio n space
through S 2 from th e sample c o n ta in e r , H.
S p e c tr a were observed endwise down th e o b serv a tio n sp a ce, 0 , through
th e one m illim e te r th ic k -q u a r tz window, ¥ .
A piezon

The window was sea le d w ith

wax t o an opening 6 mm. in diam eter and lo c a te d 18 mm. in

f r o n t o f th e end o f th e c a p illa r y o b serv a tio n sp a ce.
was as f o ll o w s .

The c o n str u c tio n

The c a p illa r y was sea le d in t o the 10 mm. e x c it e r tubes

FOR
GAS

UJ

C l.

°
f—
uj
tZ
C u -J
CO CO

<c

CM

00

LU

o

o
0 5 -)

I—f
o

E M ISS O N

f—

OBSERVATION
OF CLOW
DISCHARGE
AMD HIGH
FREQUENCY
EXCITATION.

cn

SYSTEM
CARRIER

LL)

FIGURE 2.
FLOW
SPECTRA
USING A

36

00

37

th en a sh o r t le n g th o f 6 mm. i . d . th ic k -w a lle d tu b in g was se a le d in to
th e window s id e o f th e e x c it e r tu b e .

Hie th ic k -w a lle d tube was ground

f l a t on th e end so th a t th e window could be se a le d vacuum t ig h t w ith a
minimum o f wax, so th a t th e s o lid angle ob servable through th e window
would n o t be reduced any more than n e c e ssa r y .
Hie p o r tio n o f th e apparatus from th e window back to th e d otted
l i n e , L, was supported on a la b o r a to r y jack f o r ea se o f p o s it io n in g th e
o b se r v a tio n space in th e v e r t i c a l p la n e .

The g la s s tu b in g was fa ste n e d

w ith s t r in g t o a la y e r o f w h ite p in e l / 2 i n . th ick ,w h ich in turn was
in s u la te d from th e jack by 1 /3 2 i n . o f p o ly e th y le n e f ilm composed o f
many la y e r s o f th in f il m , so th a t th e d isch a rg e tube was w e l l in su la te d
from ground.

Hie clam ps, I , sup portin g th e oth er p a rts o f th e apparatus

were no c lo s e r than one f o o t from th e e x c it e r or the o b serv a tio n sp a ce.
Glamps su p p o rtin g th e re a r p o r tio n s o f th e apparatus were in su la te d from
th e g la s s tu b in g by 1 /8 i n . b a k e lit e .
(2 )

O p tics and S p ectroph otom eter.

The sp e ctra were observed in

th e r e g io n 2200 A t o 60G0 A by means o f a Beckman Model DK-2 reco rd in g
sp ectro p h o to m eter.

Hie window o f the; d isch a rg e system was p laced approxi­

m a tely 15 cm. from th e s l i t h ousing of th e spectroph otom eter.

The d isch a rg e

in 0 was imaged on th e s l i t by means o f th e quartz plan o-convex b i c y l i d r i c a l le n s , P .

The le n s had two f o c a l le n g th s .

The c y lin d r ic a l le n s w ith

a h o r iz o n ta l a x is had a f o c a l len g th of 5 cm.

The c y lin d r ic a l le n s w ith

a v e r t i c a l a x is had a f o c a l le n g th o f 7 cm.

The le n s was p laced a t a

d is ta n c e o f 6 cm. from th e s l i t housings th e source h ou sing was removed
from th e DK-2 t o accom plish t h is .

This se t-u p o f o p t ic a l components

38

r e s u lt e d in th e maximum resp on se from th e spectrophotom eter f o r t h is
p a r t ic u la r le n s .

Furtherm ore, t h is c y lin d r ic a l le n s r e s u lte d in a

f a c t o r o f two in c r e a s e in l i g h t i n t e n s it y observed compared to any
s p h e r ic a l le n s t r ie d w ith f o c a l le n g th s ranging from 3 t o 8 cm.

The

c y lin d r ic a l le n s in crea sed th e s ig n a l str e n g th by a fa c to r o f tw enty
over th e no le n s s it u a t io n <>
A spectrophotom eter u sin g a p h o to m u tip lier was chosen f o r t h is
work b ecau se r e l a t i v e i n t e n s i t i e s o f s p e c tr a l li n e s or bands could be
determ ined v ery r a p id ly .

S ch u ler used a photographic method whereby he

changed c o n d itio n s in th e d isch a rg e s l i g h t l y and took an exposure and
rep ea ted t h i s over and o v er.

I t was f e l t th a t a spectrophotom eter would

be v e r y h e lp f u l in r a p id ly a d ju s tin g c o n d itio n s o f th e d isc h a r g e .
One could scan th e s p e c tr a l reg io n s r a p id ly m anually and g et th e r e la t i v e
i n t e n s i t i e s o f v a rio u s e m itt e r s , so th a t one would be a b le , in e f f e c t ,
t o wtu n e i n 11 on v a r io u s s p e c tr a by v a ry in g th e flo w r a te s o f th e c a r r ie r
and sample g a s e s .
r e s p o n se .

The p h o to m u ltip lie r tube was Type 1P28 w ith S£

The s e n s i t i v i t y maximum was near 3U00 A° w ith response f a l l i n g

to l e s s than XQ% a t 2000 and 6000 A° (5U)®
(3 )

The E x c it e r .

In order t o u se th e T esla c o i l e x c it e r in th e

v i c i n i t y o f th e spectrophotom eter w ith o u t in tro d u cin g e x c e s s iv e n o is e
in to th e p h o to m u ltip lie r and a m p lifie r c i r c u i t s , i t was n ecessa ry to
s h ie ld th e ca b le con n ectin g th e spectrophotom eter component case w ith
th e d e te c to r h o u sin g .

This cab le was wrapped w ith a few la y e r s o f

aluminum f o i l which were connected to a nearby w ater p ip e .

A l l c h a ssis

u n its were connected to ground u sin g heavy braided copper c a b le .

39

With t h i s arrangem ent, th e e x c it e r connected t o th e d isch a rg e system
in crea sed th e n o is e l e v e l approxim ately f i f t y p ercen t over th a t generated
i n th e instrum ent i t s e l f .

The n o is e l e v e l (measured' w ith th e tim e con­

s ta n t s e le c t o r in th e 0 .6 s e c . p o s it io n u sin g th e unattenuated p h otom u lti­
p l i e r , and 0 -1 0 # tr a n sm issio n range and maximum s e n s i t i v i t y s e t t in g )
was about 3# o f f u l l s c a le when th e e x c it e r was o p eratin g coupled to th e
d isch a r g e tu b e .

S h ie ld in g o f th e e x c it e r i t s e l f w ith a Faraday cage

seemed t o o f f e r l i t t l e or no improvement in th e n o is e l e v e l .

A pparently

th e d isc h a r g e which ca rried down th e system away from th e v i c i n i t y o f
th e e x c it e r was r e s p o n s ib le f o r most o f th e n o ise generated in th e s p e c tr o ­
photom eter by th e d isc h a r g e .
The aluminum con n ecter from th e e x c it e r t o th e g la s s tu b in g was
k ep t as sh o r t as p o s s ib le , s in c e corona d isch a rg e from t h is r e g io n was
found t o be a source o f n o is e .
The T esla c o i l i t s e l f was supported by a clamp and r in g s ta n d .
The r in g stand was in su la te d from th e m etal ta b le top which supported
th e w hole a p p a ra tu s.
one en d .

The t a b le top was sh e e t m etal and was grounded a t

Any clamp h o ld er used on the ta b le top to support th e d isch a rg e

system was a ls o in s u la te d from th e t a b le .

These supports were in s u la te d

becau se th e r e were e l e c t r i c a l cu rren ts induced in th e clamp h o ld ers
which caused n o is y a r c in g from th e bottom o f th e clamp h o ld ers to th e
su r fa c e o f th e t a b l e , s in c e th e su r fa c e s were ir r e g u la r and did n ot
make good c o n ta c t because o f d ir t and p a in t r e s id u e s .

I t was found to

be e a s ie r t o in s u la t e th e s e supp orts by p la c in g a sh e e t o f p o ly sty r e n e
or l u c i t e , or even a m agazine, under them than t o connect th e s e supports

Uo

t o ground o

I t was a ls o more s a t i s f a c t o r y , s in c e i f th e supports f lo a t e d

e l e c t r i c a l l y th e d isch a rg e c a rried p a st them more r e a d ily , and e lim in a ted
any h o t sp o ts (n e g a tiv e glcw r e g io n s) in th e tu b in g due t o an e x i t p o in t
f o r th e d isch a rg e c u r r e n t•
d o E xperim ental Procedure
(1 ) W avelength Measurement <> A c a lib r a tio n curve f o r th e s p e c tr o ­
photom eter d i a l over th e range 2537 A t o 5816 A was run u sin g a mercury
arc sou rce (Hanovia quartz typ e S-100) .

For rough w avelength measure­

ments in th e r e g io n above 3 200 A, t h is curve could be used t o g iv e an
accu racy w ith in 10 A even though th e c a lib r a tio n d id s h i f t s y s t e m a t ic a lly
w ith th e tem perature in th e room.

This s h i f t could be co rrected f o r by

m easuring th e d e v ia tio n a t th e p a r tic u la r tem perature a t th e tim e and
s h i f t i n g th e c a lib r a t io n curve t o b rin g th e d i a l read in g fo r t h is wave­
le n g th t o c o in c id e w ith th e w avelen gth .
was c o r r e c t , a t l e a s t t o

The c a lib r a tio n below 3200 A

2537 A>t o w ith in 2 A, and was as a ccu rate as

one could read from th e d i a l on th e prism .

For more p r e c is e w avelength

m easurem ents, a d is p e r s io n curve was made and w avelengths o f unknown
l i n e s were in te r p o la te d from known li n e s in th e spectrum u sin g th e wave­
le n g th s c a le expanded t o o n e-fou rth s c r o l l p er f i f t e e n in ch es o f pen
c a r r ia g e t r a v e l .

Accuracy to w ith in 5 A could th en be obtained r e a d ily

i f known l i n e s w ere w ith in about $0 A o f th e unknown one.
(2 ) O perating th e D ischarge System .

The sample liq u id was p laced

in th e sample c o n ta in e r , H, to g e th e r w ith a sm a ll g la s s c a p illa r y tube
se a le d a t one en d .

The open end of th e tube was placed below th e su r fa ce

hi

o f th e liq u id t o induce bubble form ation during the o u tg a ssin g p r o c e s s .
The sample c o n ta in er w ith th e stop cock SH was attach ed t o a vacuum l i n e
and th e sample th o ro u g h ly outgassed by b o ilin g a f t e r an i n i t i a l p eriod
o f f r e e z in g and pumping.

The sample was th en placed on th e d isch a rg e

system w ith stop cock SHc lo se d w h ile
evacuated alon g w ith th e
The second p o s i t i v e

th e space between SH and S2 was

r e s t o f th e system .
band system o f th e n itr o g e n m olecu le was a

s e n s i t i v e t e s t f o r p resen ce of a ir in th e system.; th e em issio n band o f
t h i s system h aving i t s head a t 3371 A i s very stro n g (5 5 )°

The o u tg a ssin g

was co n sid ered adequate i f th e i n t e n s it y of t h i s band head* when sample
vapor was b e in g adm itted to th e d isch a rg e sp a c e, was no g rea ter than th a t
in th e c a r r ie r a lo n e .

This i n t e n s i t y in th e spectrum o f p u r ifie d argon

was ap p roxim ately two p ercen t o f th e in t e n s it y o f th e argon d ou b let a t
U200 Ao
The flo w o f c a r r ie r gas from f la s k A was lim ite d by c a p illa r y C and
a ls o b y th e stop cock s e t t i n g a t S I .

The flo w was ad ju sted a t th e sto p ­

cock so th a t w ith th e f u l l pumping r a te of th e Welch D uo-Seal pump, th e
back p r essu re behind c a p illa r y C stood a t 10-20 mm. as r e g is te r e d by
manometer M.

At t h i s r a te o f flo w , 500 m illim e te r s p ressu re o f gas in

A would l a s t s e v e r a l h o u r s.

The i n t e n s i t i e s o f th e l i n e s in th e c a r r ie r

spectrum were n ot v ery s e n s i t i v e to t h is back p ressu re s e t t in g so th a t
th e p ressu re could vary in th e range in d ic a te d above and be m aintained
by in fr e q u e n t adjustm ent o f th e s e t t in g o f S I w ith ou t cau sin g n o tic e a b le
in te n s ity v a r ia tio n s .

With th e c a r r ie r gas flo w in g through th e d isch a rg e system , th e
e x c i t e r , E, was turned on*

The spark gap in th e T esla c o i l prim aiy was

ad ju sted so th a t th e d isch a rg e was in i t ia t e d in th e system and th e output
s l i g h t l y in crea sed t o g iv e a s t a b le d isc h a r g e .

This could be determ ined

by v i s u a l o b se rv a tio n o f th e d isch a rg e in th e tu b e .

The d isch a rg e

ca rr ied down th e system to th e vacuum pump, which acted as an in te r n a l
e le c tr o d e near ground p o te n tia l*

The d isch a rg e did n ot carry back through

th e flo w lim it in g c a p illa r y , u n le s s th e gas flo w was in ter ru p ted so th a t
th e p r e ssu r e in th a t r e g io n became low er than u s u a l.
The sample was allow ed t o v a p o r ise in t o th e d isch a rg e system through
sto p co ck s SH and S2 w h ile th e c a r r ie r spectrum was observed w ith th e
sp ectro p h o to m eter.

The flo w r a te was c o n tr o lle d by S2 so th a t th e c a r r ie r

spectrum was quenched to th e d esire d d e g ree.

The boundary o f sample

vapor and c a r r ie r gas formed was g e n e r a lly c lo s e to th e r ig h t an gle bend
in e x c it e r tu b e , F, or j u s t a l i t t l e downstream from th e r e .

Both th e

sample and c a r r ie r vapors th en were ca rried through th e o b serv a tio n space
and through th e tr a p , th e sample b ein g d ep o sited th e r e and th e c a r r ie r
p a ss in g through th e pump.
D ecom position i n th e tube was s l i g h t excep t when v ery low p a r t ia l
p r e ssu r e s o f o rg a n ic vapors were u se d .

The system was disassem bled and

clean ed w ith h o t chromic a cid clea n in g s o lu t io n between runs t o remove
tr a c e s o f p rev io u s samples adhering to th e w a lls of th e system .

h3

2o R e s u lts and D is c u s s io n
a* Quenching o f th e Argon Spectrum
At low p a r t i a l p ressu re o f any a lc o h o ls t r ie d th e r e was observed
e m issio n by CO* CH, H, H2, OH, OH* and th e arc spectrum lin e s o f argon.
This s it u a t io n corresponded t o th e d e s tr u c t iv e s t a t e d escrib ed by S c h u le r .
As th e p a r t i a l p r essu re o f th e a lc o h o l was in c r e a s e d , th e argon arc l in e s
d ecreased in i n t e n s i t y , and upon in c r e a s in g th e s e n s i t i v i t y o f th e photo­
m u lt ip lie r a m p lifie r th e r e was f i n a l l y observed about one hundred-fold
d im in u tio n o f th e argon arc spectrum to g e th e r w ith appearance o f another
spectrum , th e s tr o n g e s t l i n e s o f which are contained la r g e ly in th e b lu e
r e g io n , UOOG-5000 A.

Further vapor p ressu re in c r e a s e gave quenching o f

th e glow below th e l e v e l o f d e t e c t a b i l i t y w ith th e apparatus in u se .
S in c e th e b lu e d isch a rg e s t a t e seemed t o correspond t o S ch u lers end
s t a t e — i . e . , a t a sample p a r t ia l p ressu re j u s t b e fo re t o t a l quenching o f
th e d isc h a r g e — i t seemed t h i s m ight have been a spectrum o f a p olyatom ic
s p e c ie s o f io n iz a t io n p o t e n t ia l below th e 1 1 .5 e . v . m etastab le l e v e l of
argono

In tr y in g t o determ ine th e em itter o f th e spectrum by changing

sample v a p o rs, i t was found th a t a great number o f su b stan ces would
produce t h i s same spectrum in argon r e a d ily .
The compounds t r ie d and th e r e s u lt s are summarized in Table I .
Table l a . l i s t s th e su b sta n ces which were observed t o g iv e r i s e to th e
b lu e spectrum in argon.

Table l b . summarizes th e su b stan ces w ith w hich,

f o r one rea so n or a n o th er, th e b lu e spectrum in argon was n ot d e f i n i t e l y
ob s e r v a b le »

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U5

The samples in Table l b » which did not produce th e b lu e spectrum
i n argon were o f two ty p es s (1) su b stan ces which s tr o n g ly quenched th e
argon spectrum , such as a c e to n e , a ceta ld eh y d e, b enzaldehyde, and to lu e n e ,
and (2) su b sta n ces which appeared r e l a t i v e l y in e f f e c t i v e i n quenching
argon, such as w ater and n itr o g e n .
S in c e such v a ried su b stan ces as ben zen e, e t h y l a lc o h o l and oxygen
g a s, w ith o u t r e la t e d s tr u c t u r a l u n it s , produced t h i s spectrum in argon,
th e e m itte r must be connected w ith th e argon i t s e l f or an im pu rity con­
ta in e d in i t .

The spectrum was produced e q u a lly w e ll in p u r ifie d and

u n p u rified argon w ith no apparent change in i n t e n s i t y , in d ic a tin g th a t
th e e m itte r was n ot l i k e l y an in p u r ity in th e argon.

Moreover, i t was

found th a t when argon i t s e l f was observed in th e d isch a rg e system under
th e same c o n d itio n s o f h igh s e n s i t i v i t y as used in ob servin g th e new
spectrum , th e Hnew1* spectrum l in e s could be seen w herever th e argon arc
spectrum l i n e s did not in t e r f e r e g r e a t ly .

I t appeared than th a t a

s e l e c t i v e quenching o f l i n e s which were due to e x c ite d argon atoms was
o c cu rr in g , w h ile th er e remained many oth er l i n e s which were not quenched.;
p o s s ib ly even in some c a ses th e unquenched l i n e s were a c t u a lly enhanced.
b . The B lu e Spectrum o f Argon
The spectrum o f argon has been separated in to two groups of l i n e s
c a lle d th e red spectrum and th e b lu e spectrum which occur under d if f e r e n t
c o n d it io n s .

The d i v i s i o n o f th e argon spectrum in t o th e red and th e

b lu e s p e c tr a d a te s back to Kayser ( 5 6 ) .

He found th a t th e b lu e (spark)

spectrum i s favored by low p ressu re and a condensed d isc h a r g e , which

U6

corresponds t o a h ig h er energy d isch arge than produces th e red (a r c )
spectrumo
Co C o r r e la tio n o f th e Observed Blue Spectrum w ith th e B lu e
Spectrum o f Argon
The spectrum l i n e s of argon observed as unquenched by v a rio u s
sam ples are l i s t e d i n Table I I , to g e th e r w ith l in e s of th e argon spectrum
to which th e y correspond w ith in th e exp erim ental error o f $ A in th e
v i s i b l e r e g io n and 2 A i n th e u l t r a v i o le t r e g io n -

Of th e s e t h ir t y - e ig h t

l i n e s , a l l ex cep t s i x correspond to l in e s of th e b lu e or spark spectrum
o f a rgon The c l a s s i f i c a t i o n o f each l in e i s g iv e n in th e column la b e le d
“O rig in 11 in Table I I , “r 11 d e s ig n a tin g red and **b» d e s ig n a tin g b lu e .
In th e same column are In d ica ted a ls o th o se li n e s which have been a ssig n ed
d e f i n i t e l y t o e it h e r th e spectrum o f th e argon atom or th a t o f th e argon
ion j th e u su a l d e s ig n a tio n I or I I Is u se d .
from th e MIT W avelength T ables (57)*

The assignm ents were taken

A la r g e number o f th e l i n e s remain

u n c la s s if ie d w ith r e s p e c t to th e em itter and so have on ly red or b lu e
c la s s ific a tio n d - Helium C a rrier Gas
Helium as a c a r r ie r was a ls o used w ith benzene as th e sam ple, but
th e r e appeared t o be no s e l e c t i v e quenching o f th e helium arc spectrum .
The helium l i n e s were a l l quenched out and th e benzene r in g em issio n was
observed s tr o n g ly in th e 2600 A-2900 A r eg io n -

1+7

TABLE I I
CORRELATION OF OBSERVED SPECTRUM IN QUENCHED ARGON
WITH BLUE ARGON SPECTRUM

Observed
W avelength,
Angstroms

I n t e n s it y

Argon Line

O rigin

I n t e n s it y

a„ Benzene, QoQl* mm0 s l i t width
U nattenuated Phot o m u lt ip lie r , s e n s i t i v i t y 2 0 0 , p ercen t t r a n s . 0 - 1 0 ,
Run 3-1+1°
I+072 ± 5
1*080
1+1Q5
1+133
1*230
1*238
1*280
U372
U379
UU0 1
U+28
1*1*83
H5U6
1*576
1*587
1*607
1*658
1*728
1*736
1*768
1*810
1*881*
1*958
5005

15
6
1*
17
5
1*
50
16
5
5
16
8
36
13
20
1*0
30
28
10
69
15
1*0
15
12

1*072
1*082
1*101*
U132
1*228
1*238
1*278
1*371
1*380
1*1*0 0 , 1*1*01
1*1*31
1*1*82
1*31*5
1*579
1+590
1*610
1*658
1*728
1*736
1+765
1*806
1*880
1*958
5009

lib
b
b
lib
b
lib
lib
b
II*b
b
b
b
b
b
lib
l ib
b
b
b
b
b
b
Ir
b

150
30
200
80
l+o
1*0
80
80
80
30,1+0
80
80
200
80
150
300
150
200
1*00
150
500
300
100
200

bo l* Iso o cta n e,** Ool m . s l i t width
U nattenuated P h o to m u ltip lie r , s e n s i t i v i t y 200, p ercen t tr a n s - 0 -1 0 ,
Run 3“ 28
2893 ± 2
291+1*
2979

Ool*
3
1

2892
291*3
2979

lib
lib
lib

1*0
100
1*0

Continued

1*8

TABLE I I - C ontinued

Observed
W avelength,
Angstroms
3090 ± 5
311*0
3170
32*0
3380
3390
31*96

I n t e n s it y

Argon Line

O rigin

0 .3
0 .3
0 .2
o.U
0 .5
0 .3
3 .0

3093
3139
3170
3250
337U
3393
31*92

Ub
b
b
b
r
r
b

I n t e n s it y

50
25
50
25
300
100
50

c . B enzene, 0 .0 6 mm. s l i t w idth
U nattenuated P h o to m u ltip lie r , s e n s i t i v i t y 200, p ercen t t r a n s . 0 -1 0 ,
Run 3-1*1*
3552 ± 5
3566
3930
1*055

7*0
8 .0
U*o
6 .0

3551*
3568
3929
1*055

* T . L . Be B ruin, Z . P h y slk , 61 307 (1930)*

r
r
b
r

300
300
125
80

h9

e . P oly a to m ic M olecular S p ectra
B e sid e s th e argon phenomenon* m olecular s p e c tr a o f acetone*
a c e ta ld eh y d e , benzaldehyde* to lu e n e and benzene were observed u sin g
argon c a r r ie r as in d ic a te d in Table l b .

A ll th e se m olecu les excep t

benzene em it s tr o n g ly in th e range UQGO-^OOQ A* where th e b lu e spectrum
i s most e a s i l y observed* and i t i s p o s s ib le th e stron g m olecular
e m issio n i n t h is r e g io n obscured th e weak argon b lu e spectrum .

These

m olecu lar s p e c tr a are d escrib ed in d e t a i l in th e r e fe r e n c e s in th e
review s e c t io n o f P a rt I*

Benzene em itted stron gly* but on ly in th e

u l t r a v i o l e t r e g io n , so th e b lu e spectrum o f argon was v i s i b l e .

(The

benzene em issio n spectrum observed i s reproduced in F igu re 3> as an
example o f th e s p e c tr a o b ta in a b le w ith t h i s exp erim en tal arrangem ent.)
f . I n te r p r e ta tio n o f S e le c t iv e Quenching o f th e Argon
Red Spectrum
The organ ic samples used to quench argon w ith p rod u ction o f th e
b lu e spectrum a l l show tr a c e s o f h igh energy d eco n p o sitio n products such
as CH* OH and CO.

Furthermore* th e p rod u ction o f th e s p e c ie s 0 2

oxygen r eq u ir e s th e m oderately high energy o f about 1 1 .7 e . v .

from

These

f a c ts * to g e th e r w ith th e appearance of th e spark spectrum o f argon* show
th a t th e r e are h ig h ly e n e r g e tic p ro c e sse s s t i l l going on in a system
where th e benzene m olecule* w ith an io n iz a t io n p o t e n t ia l of on ly 9 .2 e .v .*
i s e m ittin g s t r o n g ly .

Remembering th e f a c t th a t in th e unquenched d i s ­

charge th e b lu e spectrum was p r e se n t weakly, i t appears th at* a t l e a s t in
th e system d escrib ed here* la r g e p a r t ia l p r essu res o f th e organ ic vapor
do moderate th e energy th e s p e c ie s in th e glow d isch a rg e a tta in * but

z :i8 2

o
CXI

o

6 '8 s F ::\

NO
CXI

Cu

o
o

o

°*

o

°-

CXI

o

EMISSION

xQ

o

LO

O
III
CO LO

Q

sI
UJ

O
^

z

•<

UJ

2

—

,

<

Z!
3

^

CO O
Or

UJ

$
<£
or

*—1

CO £= O
Z
c q;

u j

CO ^

UJ
Cu

D_

o
—

C\l

FIGURE 3.

o
(—
o

SPECTRUM

g ’0 9 2 ----------

W AV ELENG TH -M IILIM IC R O N S
OF BENZENE
EXCITED
WITH

ARGON

O
on

CARRIER

oo

GAS.

Tjon

51

even though th e r e i s d e f i n i t e evid en ce o f la r g e amounts o f r e l a t i v e l y
low energy e x c it a t io n p r o c e sse s occu rrin g , th e high energy end o f th e
e le c t r o n d is t r ib u t io n s t i l l remains populated to about th e same e x te n t
as i t was in th e pure c a r r ie r g a s .
The prominence o f so many s p e c tr a l l i n e s o f io n iz e d argon in a d i s ­
charge system co n ta in in g organic vapor a t n e a r ly th e same p a r t ia l p ressu re
as th e argon was su r p r isin g *

The io n iz a tio n p o t e n t ia l o f argon i s 15*8

e . v . , and th e f i r s t e x c ite d s t a t e of th e u n ip o s it iv e argon io n i s
another 13*5 e .v * above t h i s , making a t o t a l o f about 2 9 .3 e * v . requ ired
t o e x c it e an argon atom in i t s ground s t a t e to an e x c ite d s t a t e o f th e
argon io n .

T his i s f a r from th e e n e r g ie s expected in th e end s t a t e o f

th e d isc h a r g e , which should be about 10 e . v . , lim ite d b y th e io n iz a tio n
p o t e n t ia l o f th e o rgan ic v a p or.
An ex p la n a tio n o f th e occurrence o f th e high energy spark spectrum
o f argon under su p p o sed ly low energy co n d itio n s req u ir e s a d e t a ile d
c o n s id e r a tio n o f th e p h y sic s and chem istry o f system s co n ta in in g n e u tr a l
and io n iz e d argon s p e c ie s .

The o b serv a tio n s and fundam ental p ro c e sse s

proposed by p h y s i c i s t s stu d y in g such system s over a p eriod o f many years
have been e x t e n s iv e ly summarized in th e a u th o r ita tiv e review by Loeb (2 )
and summarized b r i e f l y in th e in tr o d u c tio n t o th e p resen t work.

These

f in d in g s w i l l now be d isc u sse d in r e la t io n s h ip to th e anomalous b eh avior
found d u rin g t h i s stu d y .
The in t e r p r e t a t io n o f o b serv a tio n s on io n m o b ilit ie s , Townsend co­
e f f i c i e n t s , and recom bination c o e f f ic ie n t s in in e r t gases has led t o
some u n d erstan d in g o f th e fundam ental p ro c e sse s in v o lv e d .

I t has been

52

shown th a t recom bination c o e f f i c i e n t s are v e r y sm all f o r sim p le monatom ic io n - e le c t r o n recom bination p ro cesses such as
Ar

+ e “ — -fe-

A rrt — e* Ar * hn> ,

b ecau se th e l i f e t i m e o f e x c ite d atoms ( ~ 1 0

~8

sec<>) i s so much g r ea ter
14
than th e d u ra tio n o f an io n -e le c tr o n encounter ( ~ 10
s e c .) th a t
-

th e r e i s o n ly v e r y sm a ll p r o b a b ility th a t th e e x c ite d atom can d isp o s e
o f i t s e x c e ss energy b e fo r e r e d is s o c ia t in g .

The recom bination p r o c e sse s

consuming th e p o s i t i v e io n s formed in the system more probably In v o lv e
two s te p s o The f i r s t o f th e s e i s th e th ree-b od y form ation o f th e
d ia to m ic io n
( 1 } Ar+

Ar +- M —

■?> A r 2^ •* M,

where M may be another argon atom or a fo r e ig n gas

m olecule which c a r r ie s

away th e e x c e s s energy t o s t a b i l i z e th e Ar2 « Thesecond ste p

i s th en

th e d i s s o c i a t i v e recom bination
(2 ) Ar2* * e“ — — & Ar ♦ Ar'" —

^ 2 Ar * hi> ,

which le a d s t o em issio n o f th e arc (red ) spectrum o f argon.

T his step

i s much more p rob ab le than sim ple raonatomie io n -e le c tr o n recom bination,
b ecau se h ere th e e x c e ss energy i s consumed in bond ru p tu re, which req u ires
13
-1 4
o n ly 10
- 10
s e c . , and th u s has s ig n if ic a n t p r o b a b ility o f occu rrin g
—

w ith in th e d u ra tio n o f th e io n -e le c tr o n encounter.
The e x is te n c e o f th e p o stu la te d Interm ed iate d iatom ic io n , Ar2 , at
moderate p r e ssu r e s i s w e ll e s ta b lis h e d from io n m o b ility and mass s p e c tr a l

53
stu d ies^ th e s p e c ie s k r * tends t o predominate over Ar^in pure argon* and
p e r s is t s u n t i l th e argon i s f a i r l y d il u t e in another gas*

The red (or

a r c) spectrum o f argon i s la r g e ly a s so c ia te d w ith s te p s (1 ) and (2)* and*
a t low er e le c t r o n en erg ies* w ith d ir e c t e le c tr o n impact e x c it a t io n o f
normal argon atoms <>
Loeb (2 ) (pp.. 570 - 5 7 2 ) c i t e s the p a r t ic u la r ly in t e r e s t in g s tu d ie s
o f O lsen and Huxford (5 8 )»

They stu d ied current b u ild -u p w ith pulsed*

heavy* o v erv o lted cu rren t d isch a rg es between plane e le c tr o d e s in argon
or neon a t 3 0 -7 0 mm<> p r e s s u r e <> I t was found th a t f o r th e s e gases th e
spark (o r b lu e ) spectrum a t t a in s i t s maximum i n t e n s i t y a t th e same tim e
as th e cu rrent d o e s, in d ic a tin g io n iz a tio n to be a maximum—i . e . , the
spark spectrum a r is e s from th e follcTrfing p rocesss
.

Ar

*

e

—^

Ar ' —e* Ar

Ar
* hi)

*>C“

_

—

* 2e

(spark spectrum)

The arc spectrum i n t e n s it y lagged behind th e current maximum about
f i v e m icroseconds* in d ic a tin g th a t th e e x c it a t io n o f arc lin e s depends
on secondary p r o c e sse s which can be th e s te p s ( l ) and (2 ) p o stu la te d
p re v io u sly ..
A s im ila r o r ig in i s b e lie v e d r e s p o n sib le fo r li n e spectrum o f helium*
based upon th e observed D oppler broadening of th e atom ic li n e s o f h eliu m .
The anomalous argon spectrum r e s u lt s in the p resen t study can now
be in te r p r e te d on th e b a s is th a t th e arc spectrum a r is e s la r g e ly from
d i s s o c i a t i v e recom bination o f Ar2

io n s and th a t th e spark spectrum

a r is e s from d ir e c t e le c t r o n impact io n iz a t io n p lu s e x c it a t io n o f argon
atoms t o e x c ite d argon io n s *

5U
Th© p resen ce o f organ ic m olecu les w ith many p o s s ib le io n iz a tio n
and fra g m en ta tio n p r o c e sse s in th e energy range req u ired fo r argon atom
e x c i t a t i o n w i l l tend t o consume low or in term ed ia te energy e le c tr o n s
which m ight o th erw ise d i r e c t l y e x c it e argon to e x c ite d atom ic l e v e l s .
In a d d itio n , th e o rgan ic m o lecu les may fa v o r a b ly a tta ch t o (o r complex)
th e argon ion r a d ic a ls Ar* and lim i t form ation o f Ar2* , through such
p r o c e sse s as
Ar*

* M— >

(Ar M)*

This ste p may be fo llo w e d e it h e r by n o n -r a d ia tiv e charge tr a n s fe r and
d is s o c ia tio n
(Ar M)*

1 ->

Ar

M*

or by th e d i s s o c i a t i v e recom bination p ro cesses
(Ar M)* * e~ —
(Ar M)* * e ”

Ar * M*
■>

Arw

M0

The p r o b a b ility o f form ing Ar'-' i s thus co n sid era b ly reduced <> Assuming
th a t th e co n ce n tr a tio n o f high energy e le c tr o n s i s e s s e n t i a l l y u n altered
by th e p resen ce o f th e organic sam ple, th e em ission o f th e b lu e spectrum
by Ar**, which does not depend on secondary r e a c tio n s te p s , w i l l a ls o
be u n altered o
3* S u g g estio n s f o r Further Work w ith Argon C arrier Gas
a , E ff e c t o f th e Nature o f E x c ita tio n on E lectro n
E n ergies in th e D isch arge
In work w ith argon as a c a r r ie r g a s, S ch u ler and h is co-workers have
n o t m entioned s e l e c t i v e quenching o f th e arc spectrum of argon by organic

55

vapors o

I t i s p o s s ib le th a t th e low frequ en cy e x c it a t io n method used

by S ch u ler was somehow fundam entally d if f e r e n t from th e method used in
t h i s work and did n ot e x c it e argon spark l in e s s u f f i c i e n t l y f o r them to
be observed c l e a r l y .

S ch u le r , however, has mentioned spark l i n e s as

b ein g p r e s e n t w eakly in th e glow d isch a rg e w ith o u t s p e c i f i c r e fe r e n c e
t o th e argon d isch a rg e 0 S in ce th e T esla c o i l spark i s a form of condensed
d isch a rg e h avin g h ere somewhat h igh er peak v o lta g e s than th o se used by
S c h u le r , t h i s may have favored th e b lu e spectrum o f argon enough t o a llo w
o b serv a b le v a r ia t io n s in i t s i n t e n s it y r e l a t iv e to th e r e d .

Use o f a

lew freq u en cy e x c it e r w ith in te r n a l e le c tr o d e s would a llo w t h is t o be
determ in ed .

I f th e s e l e c t i v e quenching of t h e b lu e spectrum i s s t i l l

ob served , th e in te r n a l e le c tr o d e s and lew freq u en cy source would o f fe r
some advantage f o r u se in a stu d y on r e la t iv e e f f e c t iv e n e s s o f quenchers
d isc u sse d b elo w .

With a lew freq u en cy source i t would be a sim ple m atter

t o measure in p u t energy and th e p o t e n t ia l a p p lie d .

Such measurements

are not r e a d ily made w ith th e sim ple T esla c o i l , b ecause th e ra d io ­
freq u en cy , high v o lta g e s are n ot e a s i l y a n alyzed .

Having known p o t e n t ia l

g r a d ie n ts and known p r e s su r e s , the f i e l d t o p ressu re r a t io would be
known and e le c t r o n e n e r g ie s could be e s tim a te d .
bo R e la tiv e E f f e c tiv e n e s s of Various Quenchers
There a re g rea t extrem es in th e quenching a b i l i t y o f th e compounds
s tu d ie d .

N itrogen and w ater

were both q u ite i n e f f e c t iv e in

quenching

th e argon red spectrum , w h ile

such su b stan ces as acetone and

acetald eh yde

r e a d ily quenched th e argon spectrum co m p letely , g iv in g t h e ir own
c h a r a c t e r is t ic e m issio n .

$6

The p r o c e s s e s o f in te r m o le c u la r tr a n s fe r o f e le c t r o n ic en ergy are
by no means co m p le tely understood..

A study o f th e quenching o f th e

spark spectrum o f argon by a p a r tic u la r sub stan ce as a fu n c tio n o f i t s
p a r t ia l p r e ssu r e a t a f ix e d t o t a l p ressu re could g iv e r a te d ata f o r th e
quenching p ro cess .

Such d a ta would be v a lu a b le in working out th e

mechanism o f tr a n s f e r o f e le c t r o n ic energy from argon s p e c ie s t o th e
quenching m o le c u le s »
S e v e r a l ex p erim en tal methods are a v a ila b le fo r making runs in th e
fla w in g d isch a rg e system a t v a rio u s p a r t ia l p ressu res o f organic va p o rs.
The s im p le st method would be t o prepare s o lu tio n s of th e vapor in argon
p r io r t o a run.

The vapor-argon m ixture could th en be fad in through

th e sample arm o f th e tube in Figure 2 , w h ile th e pure argon c a r r ie r gas
flo w s in through th e e x c it e r tube in th e reg u la r manner.

The flo w r a te s

o f c a r r ie r gas and ca rrier-sa m p le m ixture could be measured t o g iv e th e
p a r t i a l p re ssu r e o f organ ic vapor in th e d isch arge tu b e .
The r e l a t i v e i n t e n s i t i e s of th e red and b lu e sp e c tr a o f argon could
be measured d i r e c t l y w ith th e spectrop hotom eter.
To make a sy ste m a tic stu d y o f a number o f 11quenchers1* i t would be
h ig h ly d e s ir a b le to be a b le t o measure th e p ressu re in th e d isch a rg e sp ace.
A mercury manometer would n o t be s a t is f a c t o r y because o f th e u n d esira b le
contam ination o f th e system w ith mercury vapor w ith i t s low e x c it a t io n
p o t e n t ia l and m eta sta b le l e v e l .

Manometers made u sin g high b o il in g

org a n ic liq u id s would a ls o be u n d esira b le because o f th e a c tio n o f the
d isc h a r g e which would cause d ecom position o f th e s e l i q u i d s .
s i t i o n fragm ents would em it l i g h t in th e d isch arge sp a ce.

The decompo­
Various typ es

57

o f p r e ssu re s e n s i t i v e d e v ic e s w ith ou t th e s e sou rces o f contam ination
a r e , o f c o u r se , a v a ila b le .> A Bourdon gauge would be e s p e c ia lly s u it a b le ,
s in c e th e r e g io n o f b e s t a p p lic a b ilit y i s a few m illim e te r s o f mercury
p ressu reo

Some o f th e p o te n tio m e tr ic or quartz c r y s t a l p ressu re tra n s­

ducers r e c e n t ly a v a ila b le com m ercially m ight a ls o be a p p lied to
advantage o
Co E m ission Sp ectra in a Flow System
w ith o u t a C arrier Gas
lo E xperim ental
a » General
S in c e th e argon c a r r ie r w ith i t s com plicated em issio n spectrum was
thought t o be ren d erin g th e ob serv a tio n o f m olecular sp e c tr a o f sa tu ra ted
compounds d i f f i c u l t , some experim ents were performed u sin g a m odified
apparatus in which no c a r r ie r gas was em ployed. The p ressu re in th e
system was used t o c o n tr o l th e energy a tta in e d by th e e le c tr o n s in th e
e l e c t r i c f i e l d produced by th e high frequency T esla c o i l e x c it e r .

The

method was s im ila r t o th a t o f Kodado, Mori and Tanaka (U6) in t h e ir study
o f to lu e n e in th e glow d isc h a r g e .
bo M o d ific a tio n o f P revious Apparatus
The d isch a rg e system f o r op eration w ith ou t a c a r r ie r gas i s d ep icted
in F ig u re

The g la s s tu b in g , o b se rv a tio n space and quartz window were

th e same s i z e as d escrib ed e a r l i e r .

The sample was p laced in c o n ta in e r , H,

which was in a co n sta n t tem perature bath or c o o lin g m ixtu re.

When th e

system was evacu ated , sto p co c k , SH, h aving a 6 mm. b o r e , was opened and

UJ —
Cl_ _ J
CO CO

o

UJ

o

QD

OvJ

CO

EMISSION

§

FOR OBSERVATION
OF GLOW DISCHARGE
WITHOUT
A CARRIER
GAS.

Q_
O
Cd
O .

SYSTEM

p o

FLOW

SPECTRA

UJ

4.

UJ

FIGURE

58

Q_

59

th e sample allow ed to flo w through th e o b serv a tio n sp ace, 0 , through
th e e x c it e r tu b e , F, and through th e f lo w - lim it in g c a p illa r y , C, which
was 1 .5 mm. i.d o and 10 cm. lo n g .

The sample was d ep o sited in th e

tr a p , T, which was bathed in liq u id a i r .

Stopcock, S2, had a U mm. b o r e .

The e x c i t e r , E, was ag a in coupled to th e d isch a rg e tube by a wrapper
o f aluminum f o i l , bu t now th e coupling was moved up so th a t th ere were
o n ly th r e e in ch es between th e c e n te r o f th e aluminum f o i l and th e
o b se rv a tio n window, W.

The cou p lin g was p o sitio n e d so th a t th e d isch arge

would be as b r ig h t as p o s s ib le , y e t th e d ista n c e was s u f f i c i e n t to
p reclu d e o b se rv a tio n o f th e extrem ely h igh energy n e g a tiv e glow reg io n
around th e aluminum f o i l .

The e x c it e r c o i l was k ep t back away from the

sp ectro p h o to m eter, s in c e th e r e was not room to p o s it io n i t c lo s e t o the
aluminum f o i l w ith th e new arrangement.

Perhaps more Important was th e

f a c t th a t when th e c o i l was to o c lo s e to th e d e te c to r on the sp e c tr o ­
photom eter, e x c e s s iv e n o is y pickup from th e c o i l r e s u lt e d .

The e x c it e r

was coupled to th e aluminum f o i l through th e in n er conductor o f a th r e e f o o t p ie c e of c o a x ia l c a b le .
e le c tr ic a lly .

The ou ter conductor was allow ed to f lo a t

The w hole d isch a rg e system was In su la ted from ground by

3 /8 i n . o f p o ly s ty r e n e .

The d isc h a rg e, however, ca rried both down and

upstream from th e e x c it e r f o i l .
B ecause th e d ecom p osition occurring in th e e x c it e r f o i l was ap p reci­
a b le now w ith th e o rg a n ic vapors flo w in g d i r e c t l y through th e reg io n o f
in te n s e e x c i t a t i o n , an 18/7 ground g la ss b a l l j o in t was put in th e l i n e
between th e e x c it e r f o i l and th e window to f a c i l i t a t e c le a n in g th e
sy stem .

I t was a ls o because o f t h is stro n g decom position th a t th e

60

e x c it e r was p la ced downstream from th e o b se rv a tio n s p a c e .

In t h is

arrangement th e v o l a t i l e d ecom position products a r e , f o r th e most p a r t,
sw ept away from th e o b serv a tio n s p a c e .
The o p t ic a l system used was th e same as d escrib ed e a r l i e r .
Co Procedure During a Run
Sam ples f o r o b se rv a tio n were f i r s t ou tgassed through th e d isch a rg e
system by f r e e z in g o f f i n th e tu b e , H, w ith liq u id a i r .

The system was

pumped down fo r some tim e and th en th e liq u id was warmed and b o ile d .
This procedure was rep eated th ree or more tim es t o remove a i r .

Freedom

o f th e spectrum from th e 3371 A second p o s it iv e band o f n itr o g e n was
a g a in used as th e c r it e r io n o f adequate out g a s sin g .
The vapor p ressu re o f th e sample during a run was c o n tr o lle d by th e
tem perature o f th e b a th , B .

In some c a ses t h is was a c ir c u la t in g c o o lin g

b a th , w h ile i n most o th ers i t was a e u t e c t ic or pure f r e e z in g m ixtu re.
Temperatures were measured on a to lu en e thermometer which was c a lib r a te d
a t th r e e p o in ts s

th e f r e e z in g p o in ts of w ater and mercury, and th e

su b lim a tio n tem perature o f s o lid carbon d io x id e *

The baths w ere, however,

allow ed t o vary as much as f i v e degrees from th e s ta te d tem p eratu res,
due to p ick up o f m oistu re and subsequent change o f th e fr e e z in g p o in t s .
S p e c tr a w ere, in general* observed w ith th e stop cock s wide open,
so th a t most o f t h e p r e ssu r e drop in th e system occurred across th e
c a p illa r y , C.

In blank ru n s, u sin g a manometer to measure th e p ressu re

drop a c r o ss th e c a p illa r y w ith acetone vapor flo w in g , i t was found th a t
o n ly about f i f t y p ercen t o f th e eq u ilib riu m vapor p ressu re of th e

61

a ceton e ( a t 20 mm<> vapor p r e ssu re) was a c t u a lly dropped a cr o ss th e
ca p x lla r y ! "th© r e s t o f th e p ressu re drop probably occurred a t th e su r fa c e
o f th e liq u id i t s e l f , w ith v a p o r iz a tio n k i n e t ic s th e lim it in g f a c t o r .
I t would have been d e s ir a b le t o have n ea rly al 1 o f th e p ressu re drop
occur a c r o ss th e c a p illa r y , but t h is would req u ire such a sm a ll c a p illa r y
th a t th e flo w r a te would be inadequate t o keep th e system swept f r e e o f
d ecom p osition products <> The most s e r io u s contaminant seemed t o be carbon
monoxide, which tended t o b u ild up r a p id ly in th e system u n le s s m oderately
rap id pumping was usedo
2 . R e su lts and D is c u ss io n
a . K etones
U sing th e apparatus j u s t d escrib e d , th e em issio n s p e c tr a o f a number
o f k eto n e s were observed in th e glow d isc h a r g e .
in Table I I I .

The r e s u lt s are summarized

The continuous em ission o f aceton e could be observed f r e e

from d ecom p osition p ro d u cts, in d ic a tin g th a t th e flo w in g system was
removing d ecom p osition products ad eq u ately a t m oderately h igh sample
vapor p r e s s u r e s .

In order to observe th e aceton e em ission f r e e from

b i a c e t y l e m issio n , i t was n ec essa ry to reduce th e aceton e flo w r a te a t
• a sm a ll amount by p a r t i a l l y c lo s in g stopcock SH.

Even then th e green

b i a c e t y l em issio n could be observed downstream from th e e x c it e r , but not
in th e o b se rv a tio n space „

I t was fu rth er noted th a t th e maximum o f th e

a ceton e continuum was r e p e a te d ly observed to be a t UiOO A ± 20 A.
seems t o be a d e f i n i t e l y lo n g er w avelength than reported by both
S ch u ler (13 ) and F a u ris (22 ) .

That th e b ia c e t y l p resen t might be

This

62

TABLE I I I
KETONES OBSERVED IN GLOW DISCHARGE

Temp o
(°G j
A cetone

Vapor
P ress.
(ram<T)

Nature o f Spectrum
continuum, Amax. ItUOO Aj tr a c e
b i a c e t y l, Amax .^120
continuum, Amax. ijliOO Aj no
b ia c e t y l

0

65

0

s .c

M ethyl e t h y l k eton e

0

28

continuum, Amax. U350 A? tr a c e s
o f CO, CH

D ie t h y l k eton e

0

2 08

continuum, A max. U35 Q A> tr a c e s
o f CO, CH

D iiso p r o p y l k eto n e
B ic y e lo p r o p y l k eton e

.

continuum, A max. h3!?0 A^ much
CO, CH

25
h ea ted

2**

continuum, Amax. U350 Ay tr a c e s
o f CO, CH

C yclopentanone

25

15**

continuum, Amax. U350 Aj tr a c e s
o f CO, CH

Cycloh exanone

25

U *8

continuum, Amax. U35Q A? much
CQ, CH

heated

"Flow lim ite d by sto p cock SH«
**E stim ated from s im ila r compound.

continuum in c r e a s e s in i n t e n s it y
r e l a t i v e t o fragm ents

63

in t e r f e r in g and s h i f t i n g th e apparent maximum by adding in to th e a ceton e
spectrum seems u n lik e ly * s in c e th e aceton e maximum appears t o be in d e­
pendent o f th e b i a c e t y l maximum..

A lso th e rep orted spectrum f o r b i a c e t y l

h as i t s sh o r t w avelen gth cu t o f f a p p recia b ly above A l4.i4.OO ( 5 8 a ) » I t seems
p o s s ib le th a t* in th e case o f e x c it a t io n in t h is sy stem , th e r e may be a
new component in th e a ceton e spectrum j u s t above li3S>0 A r e s p o n sib le fo r
s h i f t i n g th e spectrum maximum t o IUiOO A.

Mien th e aceton e spectrum was

observed u sin g argon c a r r ie r gas as mentioned in Table X* th e maximum
was in accord w ith th a t rep o rted by S ch iiler and by F a u r is .
S e v e r a l oth er k eto n es were observed t o em it a continuum having a
maximum n ear U350 A*which i s in agreement w ith what has been rep orted
f o r a ceto n e and c it e d above*

The high er b o ili n g k eto n es were heated

g e n tly i n th e sample c o n ta in er cau sin g in crea sed vapor p ressu re f o r a
lon g enough tim e t o observe th e spectrum b e fo r e con den sation in th e d i s ­
charge tu b e quenched th e d isc h a r g e .

Presumably th e em issio n i s due t o

an e x c i t a t i o n o f one o f th e carbonyl group, non-bonding e le c tr o n s and i s
not a p p r e c ia b ly perturbed by th e r e s t of th e m o lecu le.
b . A le oh o ls * Alkanes * and A lk y l H alid e s
S in c e i t was found th a t m olecu lar s p e c tr a o f la r g e m olecu les could
be observed w ith th e flo w system apparatus d e sc r ib e d , th e a lip h a t ic
a lc o h o ls were a g a in su b jected t o th e discharge* as were alkanes* and
a lk y l h a l i d e s .

C h a r a c te r is tic m olecu lar s p e c tr a o f t h e s e compounds were

n ot o b serv ed , bu t i t was noted t h a t s t r ik in g changes in th e nature and
r e l a t i v e i n t e n s i t i e s o f th e sm a ll d ecom p osition fragm ents formed could

6U

be observed when th e vapor p ressu re o f th e sample was changed.

S in ce

i t was f e l t t h a t th e s e d ecom p osition p a tte r n s were p o t e n t i a l ly cap ab le
o f y i e l d i n g much in fo rm a tio n p e r ta in in g to chem ical r e a c tio n s o ccu rrin g
i n th e glow d is c h a r g e , t h i s phase o f th e work was fo llo w e d up in some
d e t a ilo

I n Table IV are summarized th e decom p osition p a tte r n s f o r some

a l i p h a t i c a lc o h o ls , a c e to n e , and a lk a n es, w h ile Table V co n ta in s th e
same ty p e in fo rm a tio n p e r ta in in g t o a lk y l h a l id e s .

In Table IV, fo r

th e a lc o h o ls and a c e to n e , th e i n t e n s i t i e s o f CH, H, Hs , and C2 are l i s t e d
r e l a t i v e t o th e U511 A band o f th e Angstrom system o f CO.

The in t e n s i t y

o f th e OH e m issio n i s l i s t e d r e l a t i v e to th e 3306 A band o f th e th ir d
p o s i t i v e system o f CO*

The r a t io o f th e Angstrom GO band and th e th ir d

p o s i t i v e band i s a ls o ta b u la ted in th e l a s t column.

For th e hydro­

carbons in Table IV and halohydrocarbons in Table V, th e i n t e n s i t i e s are
r e l a t i v e to th e U313 A band o f CH*

Other i n t e n s i t i e s are l i s t e d as 11s H

f o r s tr o n g , "m" f o r medium and ,8ww f o r weak, w ith th e m o d ifier “v 11 f o r
very.

The word ttnow i n a column in d ic a te s th a t th e s p e c ie s a t th e head

o f th a t column was n o t d e te c te d in th e spectrum*

W avelengths o f bands

observed which are n o t in th e column headings are l i s t e d in th e body o f
th e t a b le a f t e r th e i n t e n s i t y f o r th a t band.

Vapor p ressu r e s in Tables

I I I , IV and V w e r e t a k e n or e x t r a p o l a t e d from d a t a i n J o r d a n ( 5 9 ).
In some ca ses th e f lo w - lim it in g c a p illa r y was bypassed by a p ie c e
o f g la s s tu b in g .

These c a se s are in d ic a te d in th e vapor p ressu re

column by th e l e t t e r P .

6?
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67

Co I n t e r p r e t a tio n o f D ecom position P a ttern s
( 1 ) Generalo

The v a ry in g d ecom position p a tte r n s p resen ted in

T ables IV and V co n ta in much p o t e n t ia l in form ation about th e ch em istry
o f m o lecu le s under e le c t r o n bombardment.

I n te r p r e ta tio n o f such d ata

i s d i f f i c u l t , how ever, b ecause th e observed s p e c tr a l e m issio n can
r e s u l t from a v a r ie t y o f fa cto rs,; th e p r o c e sse s which can occur have
been summarized in th e In tr o d u c tio n s e c t io n .

A f i r s t approxim ation t o

th e in t e r p r e t a t io n m ight be based on th e assum ption th a t a change in
th e i n t e n s i t y o f e m issio n by a m olecu le or atom r e f l e c t s a s im ila r
change in th e t o t a l c o n c e n tr a tio n o f th e m olecu le or atom in th e
d isc h a r g e — th e b a s ic assum ption o f atom ic em issio n sp ectro g ra p h ic
a n a ly s is .

T his assu m ption , however, w i l l n ot ap ply i f th e r e a c tio n

mechanism le a d s t o form ation o f th e product m olecule in an e x c ite d
s t a t e which em its d ir e c t ly ; in e f f e c t i t assumes ra th er th a t e x c it a t io n
i s a secon d ary p r o c e ss through e le c tr o n impact and c o l l i s i o n s o f e x c ite d
s p e c ie s on m o lecu les a lrea d y formed in t h e ir ground e le c t r o n ic s t a t e s .
Furtherm ore, in th e absence o f c lo s e p ressu re c o n tr o l and measurement,
th e a v a ila b le e le c t r o n e n e r g ie s can not b e a c c u r a te ly e stim a te d .
N o n e th e le ss, some p la u s ib le in te r p r e ta t io n o f th e o b se rv a tio n s can be
made.
( 2 ) A lc o h o ls , A lk an es, A ceton e.

M olecules c o n ta in in g a C-0 bond

dem onstrate stro n g p e r s is t e n c e o f t h i s bond in th e d isch a rg e in two
w a y s.

F i r s t , th e r e i s stro n g e m issio n by th e GO m olecule which i s

u lt im a t e ly formed by d ecom p osition o f an a lc o h o l or aceton e m o lecu le.
S eco n d ly , e m issio n by C2 fragm ents i s n e a r ly ab sent from th e d isch a rg e

68

in t h e s e m o le c u le s, alth ou gh C2 i s observed r e a d ily from d eco m p o sitio n
o f hexane or many a lk y l h a lid e m o le c u le s .
An in t e r p r e t a t io n o f th e p e r s is t e n c e o f t h e C-0 bond can be made b y
e x te n s io n o f th e g e n e r a l mechanism f o r e le c t r o n im pact e x c i t a t i o n o f
a lc o h o ls proposed by Cummings and B leak n ey (5 2 ) and d e s c r ib e d e a r l i e r
in th e rev iew m a te r ia l, S e c t io n I ,

In th e i n i t i a l e le c t r o n im p act, a

non-bonding oxygen e le c t r o n i s removed from th e a lc o h o l, and th e r e s u lt in g
m o lecu le c o n ta in s an oxygen w ith a p o s i t i v e charge and an odd e le c tr o n *
The oxygen se e k s t o com pensate f o r i t s e le c t r o n d e f ic ie n c y b y form ing an
a d d itio n a l v a le n c e bond w ith th e carbon atom t o w hich i t i s a lr e a d y
bound.

The most w eak ly bonded s u b s t it u e n t i s n o rm a lly e j e c t e d t o do t h i s .

I n th e a l i p h a t i c a lc o h o ls , th e s u b s t it u e n t e j e c t e d w i l l , in g e n e r a l, be an
a lk y l group.

E ith e r th e i n i t i a l io n or a rearran ged fragm ent io n may

undergo d i s s o c i a t i v e recom b in ation t o form e x c it e d and norm al fra g m en ts.
In a d d itio n , d i r e c t e x c i t a t i o n o f th e v a r io u s s p e c ie s may le a d t o r a d ia tiv e
s t a t e s , or t o u n sta b le e x c it e d s t a t e s w hich d i s s o c i a t e , and numerous
secon d ary r e a c t io n s in v o lv in g th e r e a c t iv e fragm en ts may o c c u r .

Some o f

t h e im portant p r o c e s s e s are shown i n th e complex r e a c t io n scheme b elo w .
R
i
R - G - .OH * e'

R - C - O - H

H

H

Rearrangement^
I
H
D i s s o c i a t iv e
Recomb.

e

e“
D is s o c ia t iv e
R ecom bination

* 2e “

69

E
1
R - C»
,

RH ♦ CO* + H
+

-*
*0H

or-

or
r-*
RH ♦ CO * -H

H

©

RH 4

H-C =

D is s o c ia t iv e
Recouib.

or
-*
2RH * CO

0

l e'
H* ♦ CO
or
H** * CO

R

R
I
C
I
H

0

••

R eactant
_ E x c it a t io n .

R
I
R -

0~ H
I
H
u n sta b le

♦ e‘

D is s o c ia t io n
R T
I
R - C* ♦ •OH
I
H
or
R
I
R - C - 0* ♦ H*
f
H
or
R - C * 0 + RH .
I
H
or
Other products

">v

One or more
fragm ents may

>

carry e le c t r o n ic
e x c it a t io n

70

R
I
R - C - O - H
I
H

GO *
H2

♦

H*

_

R
I
..
R- C - O - H

+

H2

*

Product
E■
x c-ita tio n>.
—

e
e

♦

Hydrogen
A b str a c tio n

CO

Product
E x c it a t io n
TT ■*
-------— ----- ■*> H2

*

e
e

The above r e a c t io n sequence i s by no means com p lete, b ut su g g e sts v a rio u s
modes o f e x c it a t io n o f s p e c ie s le a d in g t o th e observed em ission s*
A m olecu le such as CO w ith h igh io n iz a t io n p o t e n t i a l , w i l l tend t o undergo
rep eated e x c it a t io n s w ith o u t s u f f e r in g permanent chem ical
th a t such s p e c ie s w i l l c o n trib u te much

t o th e em issio n

change, so
i f allow ed to

b u ild up in th e system ; a h ig h pumping r a te w i l l tend to sweep out such
s t a b le p r o d u c ts.

At h ig h er vapor p ressu r e s o f r e a c ta n t, th e f i e l d - t o -

p ressu re r a t i o w i l l be low er and th e e le c tr o n impact p r o c e s se s w i l l lea d
p r e f e r e n t i a l l y t o r e a c ta n t e x c it a t io n and l e s s t o io n iz a t io n .
At s u f f i c i e n t l y h igh p r e s s u r e s , o f co u rse, t h is w i l l quench th e d is c h a r g e ,
b ecau se o f la c k o f b u ild -u p o f charge c a r r ie r s , which are c o n tin u o u sly
b ein g removed by recom b in ation and am bipolar d if f u s io n .

The e x c ite d

r e a c ta n t m olecu les v e r y l i k e l y d is s o c ia t e in p referen ce t o e m ittin g ,
although no d a ta were ob tain ed a t w avelengths corresponding t o th e
t r a n s i t io n from f i r s t e x c ite d to ground s t a t e fo r the a lc o h o ls .
E x c ita tio n o f a c e to n e , as co n tra sted t o th e a lc o h o ls , le a d s t o
r e l a t i v e l y more GO and l e s s H e m issio n , and t o d e f in i t e em issio n by th e
r e a c ta n t m o lecu le i t s e l f .

Almost a l l p la u s ib le m ech a n istic p a tte r n s

71

le a d t o CO, and th e absence o f th e hyd roxyl hydrogen in aceton e a p p reci­
a b ly d im in ish es th e amount o f f r e e hydrogen formed.

The a c c e s s ib le

lo w -ly in g e x c ite d s t a t e o f aceton e i s a p p recia b ly populated by d ir e c t
e le c t r o n impact e x c i t a t i o n , p a r t ic u la r ly a t h ig h er p a r t ia l p r e ssu r e s o f
a c e to n e , and t h i s p ro cess le a d s t o th e m olecular em issio n spectrum .
The d is s o c i a t i o n which r e s u lt s from a t l e a s t p art o f th e e x c it a t io n o f
a c e to n e , as in p h o to ch em istry, lea d s t o form ation o f a c e t y l r a d ic a ls
which cou p le t o g iv e b ia c e t y l; t h e b ia c e t y l i s probably su b seq u en tly
e x c it e d by e le c t r o n im pact, although i t may form in an e x c ite d s t a t e
w hich can e m it.
The d ecom p osition em issio n p a tte r n of m ethanol i s unique among th e
a lc o h o ls s tu d ie d .

I t shows v e r y stro n g em issio n due t o io n ized carbon

d io x id e and, a t l e s s e r i n t e n s i t y , n e u tr a l carbon d io x id e and io n ized
carbon m onoxide.

These bands are prominent o n ly a t v e r y low p r e s su r e ,

and t h e ir i n t e n s i t i e s d ecrea se as th e p ressu re in th e system in c r e a s e s .
There are no apparent d iff e r e n c e s between m ethanol and th e h igh er
a lc o h o ls which seem capable o f e x p la in in g t h is b e h a v io r .

E lectro n

e n e r g ie s , how ever, are somewhat h ig h er f o r m ethanol b ecau se o f th e h ig h er
io n iz a t io n and e x c i t a t i o n p o t e n t i a l s , and th e c a r b in o l carbon atom in
th e io n has no a lk y l groups to r e le a s e .

Such p r o c e sse s as

©
GH3 OH * e~ ----- ^

[ CHS - 5 - H J ♦ 2e
t
®
2H2 * CO

and

72

o (F

.

ch3 oh

GH3 - 0 - H
ch4 +

CO

may p la y a r o l e .
aP ♦

co2

The r e l a t i v e l y weaker OH e m issio n may be due t o
OH

s- CO® .

H or

CO2 *

jP ,

and th e C02 can undergo subsequent' e x c it a t io n and io n iz a tio n to lea d t o
em issio n o f th e s p e c tr a o f C02 and C02* .
(3 ) A lk y l H a lid e s .

The h a lo g e n -c o n ta in in g s p e c ie s which em it

s tr o n g ly in an e l e c t r i c a l d isch a rg e d i f f e r among th e h a lo g e n s.

With

io d in e and brom ine, th e m olecular h alogen s can be observed r e a d ily by
t h e ir e m iss io n .

With c h lo r in e , how ever, th e main s p e c ie s ob servab le in

t h e p resen ce o f a source o f carbon-and hydrogen atoms are CC1 and HC1+ .
The d ecom p osition p a tte r n of e t h y l io d id e (T ab le V) was observed
t o d i f f e r s t r i k i n g l y a t th e low and high p ressu re extrem es run.

At th e

low p r e ssu r e , a spectrum r e l a t i v e l y high i n hydrogen and devoid o f h alogen
was observed} a t th e h ig h er p r e s s u r e , l e s s hydrogen was observed w h ile
e m issio n due t o m olecu lar io d in e became s tr o n g ly e v id e n t in th e d isc h a r g e .
In s o fa r as th e e m issio n s p e c tr a r e f l e c t r e l a t i v e c o n cen tra tio n s o f s p e c ie s
in th e d isc h a r g e , th e f o llo w in g chem ical in te r p r e ta t io n can be g iv en fo r
th e o b se r v a tio n s w ith e t h y l io d id e .
I t i s presumed th a t th e h alogen atom i s th e s i t e o f e le c t r o n impact
e x c i t a t i o n , s in c e th e non-bonding e le c tr o n s p r e se n t a good t a r g e t , as
was th e ca se w ith th e oxygen o f th e a lc o h o ls .

This e x c it a t io n r e s u lt s

73

prob ab ly i n rupture o f th e weak C-I bond, producing an io d in e atom
which can, o f c o u r se , produce I 2 w ith another io d in e atom, and a hydro­
carbon r a d ic a l or io n .
same r e s u l t .

P h otoch em ical e x c it a t io n i s known t o produce th e

The hydrocarbon fragm ent undergoes fu r th e r decom p osition

under e le c t r o n impact form ing th e hydrogen o b served .
The f a i l u r e t o ob serve m olecu lar io d in e e m issio n a t low p r essu res
may fo llo w from th e in c r e a s e in hydrogen formed in th e h igh er energy
d isch a r g e ( a t low p r e s s u r e ) .

The hydrogen r e a c ts w ith io d in e t o form

hydrogen io d id e which i s a n o n -e m itte r .

At low p r essu re where th e r e i s

much hydrogen, th e hydrogen, io d in e , hydrogen io d id e eq u ilib riu m i s fa r
in th e d ir e c t io n o f hydrogen io d id e .
I f th e p r essu re i s in c r e a s e d , e le c tr o n e n e r g ie s are reduced, and
alth ou gh C -I bonds are s t i l l r e a d ily broken, th e hydrocarbon fragm ent
i s n ot cracked so th o ro u g h ly as a t low p r e s s u r e s .

The r e s u lt i s a much

low er hydrogens io d in e r a t io and th e hydrogen io d id e eq u ilib riu m now i s
s h if t e d t o a llo w th e p resen ce o f more io d in e i n th e d isc h a r g e .
The r e s u l t w ith e t h y l bromide i s analogous t o th a t w ith e t h y l
io d id e , w ith th e a d d itio n a l o b se rv a tio n o f atom ic bromine in th e d is ­
ch a rg e.

The atom ic bromine em ission could have a r is e n d i r e c t l y in th e

d ecom p osition o f e t h y l bromide (a g a in i n agreement w ith photochem ical
o b s e r v a tio n s ), or s e c o n d a r ily from th e d is s o c ia t io n of m olecular brom ine.
S in c e th e atom ic bromine em issio n occurred much more s tr o n g ly a t h igh er
p r e ssu r e s where m olecu lar bromine a ls o was ob served , i t seems th a t most
o f th e bromine atoms observed are probably from d is s o c ia t io n o f bromine

Ik

m o le c u le s <> A*b low er p r e ssu r e s th e r e l a t i v e l y h ig h er hydrogen a v a il ­
a b i l i t y te n d s t o d im in ish th e f r e e bromine and i t s atom ic and m olecu lar
sp e c tr a .
The d a ta from c h lo r in a te d hydrocarbons in th e d isch a rg e can a ls o
be in te r p r e te d in th e same w ay.

I n t h i s c a s e , how ever, th e s p e c ie s

observed in th e d isc h a r g e i s HC1*.

I t can be se e n th a t f o r a l l th e

c h lo r in a te d hydrocarbons s tu d ie d , th e i n t e n s i t y o f th e HC1* em issio n
in c r e a se d as th e p r e ssu r e d e c r e a s e d .
fo r t h is .

Two reason s could h e lp account

F i r s t , th e h ig h e r e le c t r o n e n e r g ie s a t low p r e ssu r e would be

more e f f e c t i v e in io n iz in g th e HC1 m o lecu les p r e s e n t.

S eco n d ly , h ig h er

hydrogen c o n c e n tr a tio n s a t low p r e ssu r e fa v o r form ation o f HC1 m olecu les
in l i n e w ith th e d eco m p o sitio n p r o c e s se s p o s tu la te d f o r e t h y l io d id e
and e t h y l brom ide in th e d is c h a r g e .

The g r e a te r r e a c t i v i t y o f c h lo r in e

atoms as compared t o bromine or io d in e atoms p rob ab ly accou n ts f o r th e
la c k o f o ccu rren ce o f bands a s s o c ia te d w ith th e f r e e halogen i n th e
s p e c tr a o f c h lo r in a te d h yd rocarb on s.
3 . Summary o f Work w ith o u t a C arrier Gas
An ex p erim en ta l arrangement was d e v ise d f o r o b se r v a tio n o f th e
e m issio n s p e c tr a o f vapors and t h e ir r e l a t i v e i n t e n s i t i e s u s in g a record ­
in g sp ectrop h otom eter h avin g a p h o to m u ltip lie r d e te c to r c i r c u i t .

The

s p e c t r a l o b se r v a tio n s are rap id and capable o f y ie ld in g much in form ation
re g a rd in g ch em ica l r e a c tio n s o f e l e c t r o n i c a l l y e x c it e d s p e c ie s .
The e m issio n s p e c tr a o f flo w in g organ ic vapors e x c it e d i n a high
freq u en cy f i e l d have been observed in many c a se s t o change a p p r e c ia b ly
w ith th e p r e ssu r e in th e d isch a rg e system .

A lso i t was found th a t

75

s i g n i f i c a n t d if f e r e n c e s e x i s t in th e d ecom p osition p a tte r n s observed
f o r a number o f sim p le , r e la t e d compounds which w ere su rv ey ed .
The in t e r p r e t a t io n o f such d a ta i s h ig h ly s p e c u la t iv e , however, in
most

c a s e s a t th e p r e s e n t t im e . At th e e n e r g ie s a v a ila b le , an enormous

co m p le x ity o f p o s s ib le r e a c t io n p ath s must be c o n s id e r e d .

Perhaps th e

mopt s u r p r is in g a s p e c t i s th e a p p recia b le e f f e c t r e l a t i v e l y s u b tle
s t r u c t u r a l d if f e r e n c e s seem t o e x e r t on th e s p e c t r a l b e h a v io r .
With th e a p p lic a tio n o f th e co n v en ien t reco rd in g sp ectrop h otom eter,
w hich m easures r e l a t i v e i n t e n s i t i e s alm ost d i r e c t l y , th e f i e l d o f i n v e s t i ­
g a tio n should be cap ab le o f rapid grow th.
U* S u g g e stio n s f o r F urther Work w ith o u t a C a rrier Gas
A l l o f th e system s s tu d ie d

in t h i s work show prom ise o f y ie ld in g

in t e r e s t in g ch em ical in fo rm a tio n upon more d e t a ile d in v e s t ig a t i o n .
E x te n sio n o f th e o b se r v a tio n s w ith comparable s e n s i t i v i t y in to th e
vacuum u l t r a v i o l e t would y i e l d i n t e r e s t in g in fo rm a tio n regard in g th e
e x te n t o f d ir e c t e x c i t a t i o n o f s a tu r a te d m o lecu les to s t a b le e x c ite d
e le c tr o n ic l e v e l s .
For fu r th e r stu d y o f fra gm en tation p a tte r n s in th e T e sla d isc h a r g e ,
p r e s su r e s should be known more a c c u r a t e ly .

The measurement o f p ressu re

in th e d isc h a r g e space as d isc u s se d in th e l a s t s e c t io n would be ap p lied
h ere.

With p r e ssu r e s a c c u r a te ly known in th e d isc h a r g e sp a c e, e le c t r o n

e n e r g ie s can be more a c c u r a te ly estim a ted and compared from compound t o
compound.

V a r ia tio n o f th e fragm en tation p a tte r n o f a given compound

co u ld be o b tain ed as o f fu n c tio n o f p r e ssu r e (o r f ie ld - t o - p r e s s u r e r a t i o ) ,

76

and c le a r cu t c h a r a c t e r i s t i c s m ight be observed w hich would h e lp to
fo rm u la te breakdown mechanisms in th e glow d is c h a r g e .
These fr a g m e n ta tio n p a tte r n s could form th e b a s is o f a method o f
q u a l i t a t i v e i d e n t i f i c a t i o n o f vapor phase components in gas chromatography.
T his a s p e c t w iH be d isc u s se d more f u l l y i n P a rt I I o f t h i s work.
In some c a se s i t may be b e t t e r t o u se a flo w in g c a r r ie r gas t o
d i l u t e th e o rg a n ic vap ors so th a t t h e se v e r e quenching and i n s t a b i l i t y
o f th e d isc h a r g e which occur

w ith th e pure o r g a n ie s a t r e l a t i v e l y low

vapor p r e ssu r e s are l e s s e n e d «
Chem ical a n a ly s is o f p ro d u cts from glow d isch a rg e e x c it a t io n o f
vapors i s a h ig h ly im portant l i n e o f fu r th e r work t o be a p p lied t o th e
in v e s t ig a t io n o f r e a c t io n mechanisms in th e d is c h a r g e .

PART I I
APPLICATION OF THE TESLA GLOW DISCHARGE TO
GAS CHROMATOGRAPHY DETECTION

TABLE OF CONTENTS

Page
A. I n t r o d u c t io n . * . * * . * . *

o

„

*

. . o

*

o

. ...............

77

B. B r ie f Summary o f D e te c to r s f o r Gas Chromatography........................

79

C. P r o p e r tie s o f th e T e s la E x cited Glow D isch arge Amenable to
Measurement. . . . . . . . . . . . .
...............

8U

D . E x p erim en ta l o

86

o o . . . . . .

. 0 . . 0 . . 0 . 0

.

. . .

. . . . . . . . . . . . a

. . . . . . . . . . . . . . . . .

1 o Its a g en t s . 000 . o . . o o . o . . o . * o o o . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
86
86
a . Compressed Gases . . . . . . . . . . . . . . . . . ........................ ..................
b o AIT 0 0 . 0 . 0 . 0 0 0 0 . . . . . . . 0 0 . * . . . . . . . . . a . o »«»«*««
87
c . N a tu ra l Gas
...........................
87
d . Organic L iq u id Sam ples . . . . . . . . o o o . . . .
.........................
87
2 o Apparatus
.............
87
a o G eneral D e s ig n
...............
87
b . D e te c to r C o n s tr u c tio n .
....................
89
(1 ) M echanical D e t a i l of S en sin g E le m e n ts.................
89
( 2 ) E x c ite r Tube ...........
92
( 3 ) E l e c t r i c a l C ir c u it s
................ 9 J4
(a ) G e n e r a l . . . . . . . . . . . . . . . . . . . ......................
9k
(b) E l e c t r i c a l D e t e c t o r
..................
9k
( c ) P h otom etric D e t e c t o r
97
c . The Flow S ystem
..........
97
( 1 ) G e n e r a l.
.............. 97
(2 ) O p eration w ith o u t a Chromatographic C o lu m n .... 99
(3 ) Oxygen S ca v en g er .................................
100
3 o E xperim ental P ro ced u re
.............
100
a . G eneral D e t a i l s
................
100
(1 ) Sam pling Techniques
............100
(2 ) P r essu re and Flow R a t e . . . . . . . . . . . ...............
102
^3 } Chromatograms.
.
.
.
.
o
.
103
b o Procedure U sing th e p h otom etric D e te c to r ..................................
103
c . Procedure U sing th e E l e c t r i c a l D e t e c t o r .* . . . . . . . . . . . . 103

Eo R e s u lts and D i s c u s s i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

105

1 o P h otom etric O b s e r v a t i o n s • . . . . . . . . . . . • • . e . . . » • • • * . • » • . . • • • » • 105
a . Ge ne r al . . . . . .
......
105
b o O v e r -a ll L ig h t I n t e n s i t y .
......................
106
continued

TABLE OF CONTENTS - C ontinued

Page
co Quenching o f C a rrier Gas Spect rum. . . . . . . . . . . . . . . . . . . 108
d . S e l e c t i v e O b servation o f E m ission by th e S a m p l e . . . . . 108
e . Q u a lit a t iv e A n a ly sis o f Chromatographic Com ponents.. 10 9
f o S t a b i l i t y o f th e Di s c h a r g e . . . . . . . . . . . . . . . . . . . . . . . . . . 112
g . Summary . . . . . . c . . . . . . . . . . . . . . .
...........
113
2. The E Q e c tr ic a l D e te c to r -R e s u lts and D i s c u s s i o n . . . . . . . . . . . . 113
a. S e le c t io n o f System s t o Study and D ischarge
O perating Co n d i t i o n s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
{1^ C a rrier Ga s e s . . o . . o o o . . . . . . . . . . . . . . . . . . . . . . . . 113
(2) Apparent E l e c t r i c a l C h a r a c te r is tic s o f th e
D e te c to r D i s c h a r g e . . . . o . . . . . . . . . . . . . . . . . . . 11)i
(3 ) E f f e c t o f P r e ssu r e on D e te c to r P r o p e r t i e s . . . . 11?
b o R esponse o f D e te c to r U sing A ir Ca r r i e r . . . . . . . . . . . . . . 123
...............123
( 1 ) L ig h t Gases
(2 ) R e p r o d u c ib ilit y .
...........
126
(3 ) H igher Hydrocarbons
................... 127
127
(U) Water V a p o r . . . . . . . . . . . . . . . . . . . . . . . . . . . ...........
c . Response o f D e te c to r U sing Argon Ca r r i e r . . . . . . . . . . . . 128
( 1) Oxygen S ca v en g er
...........................
128
.............
128
(2 } Methane
(3 ) H igher Hydrocarbons
...........................
130
(10 Organic L iq u id s
............ 133
(5 ) A i r . o. o. . . . o. . . . . . . . . . . . o. . . . . . . . . . . . . . . . . . . . 133
( 6) Sample C h ro m a to g ra m s......................
133
d . I n flu e n c e o f D e te c to r Geometry on S e n s i t i v i t y . . . . . . . 138
...........
139
e . Summary
f . I n t e r p r e t a tio n o f E le c t r i c a l D e te c to r R e s p o n s e . . . . . . 11*0
F . Comparison o f th e P h otom etric and E l e c t r i c a l T esla D isch arge
DetectO rS . ooo. o * o . o o o o o . . o o . o o c . o . o * . o o o o o » e .
. . . o o o * . *1.)|J|
1.
2.
3°
ko
5.

S e n s i t i v i t y . . . . . . . . . . . . o. . . . . . . . . . . . . . . » . . . . . . . . . . « . . . . . . .
R ete n tio n Volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
L in e a r it y o f Re s pons e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C a rrier Gases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Selectivity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

G. S u g g e stio n s f o r A p p lic a tio n s and F urther Work
1o
2.
3.
1*.

.........................

"1)1)f
lUU
11*5
11*5
11*6
11*6

L ectu re D em onstration and P r e p a r a tiv e Work
...........
11*6
H um idity Measurement
................. 11*8
Vapor P r essu r e and M olecular W eight D e t e r m i n a t i o n . . . . . . . . . 11*8
Q u a lit a t iv e A n a l y s i s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H*9
............ 11*9
a . G en era l
continued

TABLE OF CONTENTS - Continued
Page
b o Rapid Scanning Spe ctrophotom etry
• » • • • • • • 150
Co Te s l a B is charge Cr a c k mg o o o . o o a . o . o o o o o e e o o . 0 . * . . o # * 150
5o High M olecular W eight Compounds. . . . . .
...............
151
Ho O v e r -a ll Summary o f E l e c t r i c a l D e te c to r s f o r Gas Chromatography. 151

Ao I n tr o d u c tio n
D uring th e cou rse o f th e in v e s t ig a t io n o f th e quenching o f th e argon
spectrum b y v a r io u s org a n ic vapors d escrib ed in P art I , i t became ev id e n t
th a t th e glow d isc h a r g e in a flo w in g c a r r ie r gas which was e x c ite d by a
T esla c o i l had p r o p e r tie s which could be used to d e t e c t fo r e ig n components
in th e c a r r ie r g a s »

I t was a lr e a d y known from o b se rv a tio n o f s p e c tr a in

th e glow d isc h a r g e e x c ite d in t h i s manner, th a t th e d isch a rg e was q u ite
s ta b le 0 The i n t e n s i t i e s o f s p e c t r a l l i n e s o f th e c a r r ie r gas when
d e te c te d b y th e p h o to m u ltip lie r c i r c u i t o f th e spectrop hotom eter were v e r y
e a s i l y r ep r o d u c ib le t o w ith in about (t e n p e r c e n t.

Furtherm ore, when organic

sam ples were in tro d u ced in t o th e d isc h a r g e , d r a s t ic changes in th e spectrum
occu rred , and th e s e were e a s i l y d e te c te d by th e p h o to m u ltip lie r c i r c u i t .
The f a c t th a t d eco m p o sitio n p a tte r n s f o r v a r io u s compounds could be d i f ­
f e r e n t ia t e d by th e em issio n d e te c te d by th e spectrop hotom eter su g g ested
a d d it io n a lly th a t i t might be p o s s ib le t o d is t in g u is h components in th e
c a r r ie r gas which con tain ed d if f e r e n t e lem en ts, or p o s s ib ly m erely
d i f f e r e n t f u n c tio n a l g ro u p s»
With th e above id e a s in mind, an in v e s t ig a t io n was undertaken to
su rvey th e p o s s i b i l i t i e s o f th e T e sla e x c ite d glow d isch a rg e ap p lied to
d e t e c tio n o f components e f f lu e n t from a gas chrom atographic column.
Toward t h is end, i t was n e c e s sa r y t o fin d out whether or not th e s e n s i­
t i v i t y o f such a d e te c to r would be in a range which could be u s e f u l in
chrom atographic work <>

11

?8

B ecause th e e x c i t e r i t s e l f was so in e x p e n siv e and sim p le t o c o n str u c t
and o p e r a te , i t seemed d e s ir a b le t o determ ine w hether or n ot a se n sin g
elem ent f o r a glow d isc h a r g e d e t e c to r could be d ev ise d which a ls o could
be c o n str u c te d e a s i l y and in e x p e n s iv e ly .

A d e te c to r u n it c o n s is t in g o f

a sim p le la b o r a to r y le a k t e s t e r e x c it e r and an in ex p en siv e s e n sin g elem ent
would be o f v a lu e in s it u a t io n s where e la b o r a te gas chrom atographic
i n s t a l l a t i o n s were e it h e r in co n v en ien t or p r o h ib it iv e ly exp en sive,,
The v i s u a l resp o n se is s u e d by th e d isch a rg e in th e p resen ce o f o rgan ic
components co u ld , c l e a r l y , be u s e f u l in le c t u r e dem onstration o f gas
chrom atographic p r in c ip le s or in undergraduate la b o r a to r y program s.

In

a d d itio n t o t h i s , a sim p le d e t e c to r which any la b o r a to r y could co n str u c t
would be v a lu a b le to th e s y n t h e t ic chem ist b ecau se p r e p a r a tiv e gas
chrom atographic columns a r e , in g e n e r a l, r e a d ily a v a ila b le or s e lf-p r e p a r e d
w ith o u t much expense 0

Much p r e p a r a tiv e work needs o n ly a r e l a t i v e l y crude

in d ic a t io n o f when th e main component le a v e s th e column.

The d e te c to r s

p r e s e n t ly a v a ila b le f o r a n a l y t ic a l work which are a ls o used f o r p rep a r a tiv e
work a re g e n e r a lly more e la b o r a te th an i s n e c e ssa r y f o r much organ ic
p r e p a r a tiv e work.

I t seemed p o s s ib le th a t even th e v i s u a l in d ic a tio n of

th e d isc h a r g e m ight be adequate f o r t h is ty p e o f work.
A b r i e f rev iew o f v a r io u s d e te c to r s which are employed in gas chroma­
tography w ith s p e c ia l em phasis on th o se which seem more c l o s e l y r e la te d to
th e p r e se n t i n v e s t i g a t i o n i s p resen ted b elo w .

79

Bo B r ie f Summary o f D e te c to r s f o r Gas Chromatography
Gas chrom atographic d e t e c to r s in u se or developm ent tod ay b e lo n g f o r
th e most p a r t t o e it h e r o f two t y p e s .

P robab ly th e most commonly found

d e t e c to r to d a y i s one which responds to changes in th e therm al c o n d u c tiv ity
o f th e column e f f l u e n t 0 Such a d e te c to r i s c a lle d sim p ly a therm al
c o n d u c t iv it y c e l l , or by th e more r e c e n t ly coin ed term , katharom eter.

The

second ty p e o f d e t e c to r c o n s is t s b a s i c a l l y o f two more or l e s s d i s t i n c t
u n its? an e x c it e r which a c t iv a t e s or io n iz e s th e c a r r ie r gas and sample
e f f lu e n t from th e column, and a se n sin g elem ent which responds t o a ch an ge.
in a p r o p er ty o f th e e x c ite d g a s , when a sample i s p resen t*

Examples of

th e second ty p e o f d e t e c to r a re th e ’’io n iz a t io n gauge d e t e c to r ” o f Ryce
and B ryce ( 6 0 ) , th e ”flam e i o n iz a t io n d e t e c to r ” o f McWilliara and Dewar ( 6 1 ) ,
th e ”b e t a -r a y io n iz a t io n d e t e c t o r ” o f L ovelock ( 6 2 ) , th e wglow d isc h a r g e
d e t e c t o r ” o f H arley and P r e to r iu s ( 6 3 ) , and th e ”ra d io freq u en cy d isch a rg e
d e t e c to r ” o f Karmen and Bowman (61;).

The im portant f e a tu r e s o f th e s e

d e t e c t o r s w i l l b e d isc u s se d b r i e f l y in th e fo llo w in g paragraphs.
A k a th a ro m eter-ty p e d e te c to r may employ as th e s e n s in g elem ent a
th e r m is to r , or a tu n g s te n w ir e , or some oth er h ea t s e n s i t i v e elem en t.

The

s e n sin g elem en t i s u s u a lly b alanced i n 1a 'Wheatstone b rid g e c i r c u i t , t o
h e lp com pensate f o r f lu c t u a t io n s in tem p eratu re, flo w r a t e , e t c .

Therm istor

k atharom eters have a l i m i t o f d e t e c t a b i l i t y o f components in th e range of
_s
10
grams, w h ile tu n g s te n w ire d e t e c to r s a re s l i g h t l y l e s s s e n s i t i v e a t
room tem p eratu re *

These d e te c to r s are e s s e n t i a l l y f r e e from n o is e , b u t

g e n e r a lly e x h ib it lo n g term d r i f t .

These d e t e c to r s have th e v e r y d e s ir a b le

80

p ro p e rty t h a t th e y are u n iv e r s a lly s e n s it iv e * alth ou gh th e magnitude o f
resp o n se f o r a p a r t ic u la r component depends on i t s therm al c o n d u c tiv ity .
K atharom eter d e t e c to r s have r a th er la r g e volumes f o r many p u r p o ses.

The

volume i s about o n e -h a lf m i l l i l i t e r .
K atharom eters can t o l e r a t e a range o f c o n c e n tr a tio n s o f sample o f one
th o u sa n d -fo ld w ith l in e a r resp on se and w i l l n ot s a tu r a te a t any sample
c o n c e n tr a tio n .

The s ig n a l from th e s e d e te c to r s i s th e order o f about 0 -1 0

m i l l i v o l t s , which n e c e s s i t a t e s a v e r y s e n s i t iv e in d ic a tin g d e v ic e .

Summing

up t h e s e p r o p e r tie s* th e katharom eter d e te c to r has many good f e a t u r e s ,
but i t s s e n s i t i v i t y i s n o t as h igh as i s d e s ir a b le and i t s dead volume i s
r a th er h ig h f o r much work b e in g done to d a y , e s p e c i a ll y s in c e th e advent o f
th e Gola y c a p illa r y - t y p e chrom atographic columns.
D e te c to r s in v o lv in g e x c it a t io n o f th e c a r r ie r gas and sample m ix tu re,
which th en se n se a p ro p erty o f th e e x c ite d su b sta n ces are more d i r e c t l y
r e la t e d t o th e p r e se n t work and have r e c e iv e d a g r e a t d e a l o f a t t e n t io n
v e r y r e c e n t ly in a search f o r d e te c to r s more s e n s i t iv e than th e katharom eter.
This i s t o a la r g e e x te n t b ecause o f th e la c k o f adequate s e n s i t i v i t y o f
th e katharom eter f o r c a p illa r y colum ns.

Furtherm ore, th e dead volume o f

t h e s e io n iz a t io n - t y p e d e t e c to r s can be made in th e m ic r o lit e r r e g io n
req u ired by c a p i l l a i y columns t o p rev en t t a i l i n g o f peaks and l o s s o f
r e s o lu tio n .
The a i o n iz a t io n gauge d e t e c to r 11 o f Ryce and Bryce (6 0 ) in v o lv e s
m o d ific a tio n o f a standard io n iz a t io n gauge so th a t th e gas flo w s d i r e c t l y
betw een th e e le c t r o d e s •

E le c tr o n s are em itted from a h o t fila m e n t and

a c c e le r a te d toward a p o s i t i v e l y charged g r id .

These p o s i t i v e io n s are

81

c o lle c t e d on a n e g a t iv e ly charged p l a t e .
c u le s in th e gas streamo

These e le c t r o n s io n iz e mole­

The gauge o p era tes a t a f r a c t io n o f a m illim e te r

p ressu rec

About o n e -h a lf p er cen t of th e gas stream i s b led in t o th e

d e te c to r o

The grid o f th e io n iz a t io n gauge i s h eld s l i g h t l y l e s s p o s it iv e

than th e p o t e n t i a l req u ired t o io n iz e th e c a r r ie r g a s , th ereb y g iv in g a
v e r y low—le v e l background c u r r e n t.

To make th e d e te c to r u n iv e r s a l in i t s

s e n s i t i v i t y , th e u se o f h eliu m c a r r ie r gas i s n ecessary, b ecau se th e
d e t e c to r i s n o t s e n s i t i v e t o any sample w ith an io n iz a t io n p o t e n t ia l above
t h a t o f th e c a r r ie r .

The d e te c to r i s i n s e n s i t i v e t o flo w r a te and p r essu re

changes in th e main gas stream and t o sm a ll changes o f tem perature and
p r e ssu r e in th e d e te c to r „

The s e n s i t i v i t y i s two hundred tim es th a t o f

th e th e r m isto r d e te c to r , and p o t e n t i a l l y a thousand tim es more s e n s i t iv e
than th e th e r m isto r d e te c to r as dem onstrated by G u ild, L loyd, and Aul (65) •
The ‘*flame io n iz a tio n d e t e c to r 11 o f McWilliam

and Dewar ( 6 l) i s th e
13
most s e n s i t i v e d e t e c to r d ev ised f o r a l l excep t l i g h t gases ( ^ 1 0
g/cc.) •
-

I t a llo w s u se o f n itr o g e n as a c a r r ie r g a s .

The column e f f lu e n t Is mixed

w ith a v e r y sm a ll amount o f hydrogen and th en combusted in cle a n a i r .
The flam e emanates from a sm a ll m etal j e t which s e r v e s as th e p o s it i v e
e le c tr o d e o f an e l e c t r i c a l c o n d u c tiv ity c e l l ] th e n e g a tiv e e le c tr o d e i s a
platinum gauze lo c a te d c lo s e t o th e j e t .

The e l e c t r i c a l c o n d u c tiv ity o f

th e gas flam e changes as sample vapors come through th e column.

The

d e te c to r i s ex trem ely s e n s i t i v e ex cep t f o r l i g h t ga sesj i t w i l l not d e t e c t
n itr o g e n , hydrogen, oxygen, carbon d io x id e , ra re g a s e s, h a lo g en s or w a te r .
The background cu rren t i s v e r y low and s t a b l e .
in th e m ic r o lit e r r a n g e .

The d e t e c to r volume i s

The d e t e c to r i s q u ite i n s e n s i t i v e t o tem perature

82

changeso

The d e t e c t o r s a tu r a te s a t low co n cen tr a tio n s compared t o a

katharom eter .

S ig n a ls are o f th e order o f 10 m ic r o v o lts .

The ^beta^ray i o n iz a t io n detector** d ev ised b y L ovelock (6 2 ) i s an other
form o f io n iz a t io n d e t e c t o r .

A r a d io a c tiv e source i s used to e x c it e th e

c a r r ie r g a s , which in tu rn e x c it e s sample m o lecu les and io n iz e s them.
The c a r r ie r and sample p a ss through a m etal je t,w h ic h i s th e p o s i t iv e
e le c tr o d e o f an e l e c t r i c a l c o n d u c tiv ity c e l l .

The n e g a tiv e e le c tr o d e i s

a h o llo w m eta l b lo ck which co n ta in s th e r a d io a c tiv e source and in to which
th e gas flo w s through th e p o s i t i v e e le c t r o d e .

The io n iz a t io n current

betw een th e j e t and d e t e c to r b lo ck c o n s t it u t e s th e s ig n a l .
i s operated a t atm ospheric p r e s su r e .

The d e t e c to r

The c a r r ie r g a s, in order t o be

e f f e c t i v e , shou ld be a r a r e g a s, s in c e th e ra re g a ses p o s s e s s lo n g - liv e d
ra eta sta b le s t a t e s w hich a t t a i n h igh co n ce n tr a tio n s upon con tin u ed ir r a d i­
a t io n .

These m e ta sta b le atoms are th e agents which io n iz e th e sample

m o le c u le s .
d e te c to r .

Com m ercially a v a ila b le argon i s o f adequate p u r ity f o r t h i s
Helium a v a ila b le com m ercially i s n ot pure enough.

S in c e i t s

ra eta sta b le l e v e l i s so v e r y h igh (20 e . v . ) , im p u r itie s o f low io n iz a t io n
p o t e n t i a l d ep o p u la te t h i s s t a t e r a p id ly .
a t about 1 1 .5 e . v .

The argon raetastab le l e v e l i s

S in c e th e s e raetastab le atoms are th e predominant

io n iz in g a g e n ts , m o le cu le s w ith io n iz a t io n p o t e n t ia ls above 1 1 .£ e*v.
w i l l n ot b e d e te c te d in t h i s system , and such im p u r itie s as n itr o g e n ,
oxygen, w a te r , neon, h eliu m , or hydrogen w i l l n ot i n t e r f e r e .

B e sid e s

b ein g i n s e n s i t i v e t o th e same su b sta n ces as th e flam e io n iz a t io n d e t e c t o r ,
th e ^ b e ta -r a y io n iz a t io n d e t e c to r 11 w i l l not respond to Cx and C2 hydro­
carbons b eca u se o f t h e ir h igh io n iz a t io n p o t e n t i a l s .

The s e n s i t i v i t y i s

83

s l i g h t l y l e s s th an th a t o f th e flam e io n iz a t io n d e te c to r (2 x 10

m oles

d e t e c t a b l e ) , b u t much g r e a te r th an a therm al c o n d u c tiv ity d e t e c t o r .

The

d e t e c to r s a tu r a t e s a t a l o w - le v e l sample c o n c e n tr a tio n in th e c a r r ie r
compared t o a k ath arom eter.

The s ig n a l r e q u ir e s h ig h a m p lific a tio n *

The glow d isc h a r g e d e t e c t o r of H arley and F r e to r iu s (6 3 ) sim p ly
m easures th e change in v o lta g e drop between two e le c t r o d e s e x c it in g a
d i r e c t cu rren t glow d isch a r g e in th e column e f f l u e n t g a s e s .
u t i l i z e s an a p p lied v o lta g e o f 900 V.

The d isc h a r g e

When sample vapors come through

th e d e t e c t o r , th e v o lta g e drop changes by s e v e r a l v o l t s * Such a d e te c to r
i s u n iv e r s a l in i t s r e sp o n se , b u t th e d e te c to r i s somewhat u n s ta b le , accord­
in g t o Karmen and Bowman (6Ub) *
Karmen and Bowman (61;) have r e c e n t ly d e v ise d a glow d isch a rg e d e te c to r
which u s e s a ra d io fr eq u e n c y e x c i t e r .

I t was found th a t helium a t atmos­

p h e r ic p r e ssu r e can be io n iz e d t o form a glow d isch a rg e by th e u se o f a
ra d io fr eq u e n c y v o lta g e in trod u ced in to th e c a r r ie r stream by an in t e r n a l
e l e c t r o d e « T his e le c tr o d e was surrounded by a c o n c e n tr ic e le c tr o d e , which
was th e ca se o f th e d e t e c t o r .

There i s a p a r t ia l r e c t i f i c a t i o n o f th e

ra d io fr eq u e n c y v o lta g e due t o th e asymmetry o f th e e le c tr o d e system .
The d ir e c t cu rren t component can be sep arated from th e ra d io freq u en cy
v o lta g e by proper f i l t e r c i r c u i t s .
i s t i c o f th e c a r r ie r g a s .

There i s a s te a d y cu rren t ch a ra cter­

With h eliu m c a r r ie r gas t h is cu rren t i s

d ecrea sed when o rg a n ic vapors p ass through th e d e t e c to r .

This quenching

cu rren t may be o f th e order o f microamperes and can be r e g is te r e d by a
r e l a t i v e l y sim p le m eter.

The o p era tio n o f t h i s d e te c to r w i l l be d isc u s se d

more f u l l y in a l a t e r s e c t io n , becau se i t has much i n common w ith a d e t e c to r

8U

d e v ise d in d e p en d en tly in th e p r e se n t i n v e s t ig a t io n .

The ra d io freq u en cy

d e t e c to r i s more s e n s i t i v e than a k atharom eter, b u t has n ot b een shown
t o be as s e n s i t i v e as t h e flam e io n iz a t io n d e t e c t o r .

Karmen and Bowman

(6Ub) r e p o r t th e minimum d e t e c ta b le l im i t f o r C12 compounds t o be 10

12

m oles o The f r a c t i o n a l d e c re a se in th e d ir e c t cu rren t i s d i r e c t l y pro­
p o r t io n a l t o th e c o n c e n tr a tio n o f th e organic vapor in th e helium c a r r ie r .
Neon c a r r ie r behaves p r a c t ic a l l y l i k e helium , ex cep t t h a t a s l i g h t l y h ig h e r
v o lta g e i s n e c e ssa r y to maintain, th e d isc h a r g e .
h ig h e r v o lt a g e t o s t a r t th e d is c h a r g e .

Argon r e q u ir e s a y e t

With argon , low c o n c e n tr a tio n s

o f o rg a n ic vapor in c r e a s e th e c u r r e n t, w h ile h ig h e r co n cen tr a tio n s d e c rea se
th e c u r r e n t.
There have been numerous o th er d e te c to r s d e v ise d f o r gas chroma­
to g ra p h y , bu t none seem t o o f f e r more in s e n s i t i v i t y or s im p l i c i t y than
th o s e j u s t d e s c r ib e d .

For t h i s reason i t was f e l t t h a t developm ent o f a

sim p le d e t e c to r f o r u se in many a p p lic a tio n s would be w o r th -w h ile .
C. P r o p e r tie s o f th e T e sla E x cited Glow D ischarge
Amenable to Measurement

The T e sla c o i l s e t s up a h igh v o lta g e (ab ou t 50 Kv . ) , h igh freq u en cy
(about 3 m egacycles p er second) e l e c t r i c a l f i e l d , which i n i t i a t e s and
m a in ta in s a v i s i b l e glow d isc h a r g e in most g a se s a t reduced p r e s s u r e .
P r elim in a ry experim ents showed th a t in argon and helium c a r r ie r g a ses
th e v i s i b l e d isc h a r g e can be m aintained a t p re ssu r e s above one atm osphere,
w h ile f o r a ir and n itr o g e n , th e d isch a rg e was s c a r c e ly v i s i b l e a t 350 mm.
p ressu re.

The d isc h a r g e i s v i s i b l y a lte r e d by sm a ll q u a n t it ie s o f f o r e ig n

85

g a s e s , b o t h b y new e m i s s i o n f r o m t h e f o r e i g n g a s a n d , u s u a l l y , b y q u e n c h ­
in g o f t h e

c a r r i e r g as s p e c tru m *

T hese p r o p e r t ie s

o f th e d is c h a rg e

s u g g e s te d t h a t a d e t e c t o r c o u ld b e c o n s tr u c te d u s in g a p h o to c o n d u c tin g
c e ll as th e
to

is o la te

s e n s in g e le m e n t, w ith
a p o rtio n

s a m p le c o n c e n t r a t i o n

a p p ro p ria te lig h t f i l t e r s ,

i f n e c e ssa ry ,

o f t h e s p e c t r u m w h ic h c h a n g e d s t r o n g l y w i t h t h e
in th e

c a r r i e r gas*

T he b l u e - g r e e n e m i s s i o n b a n d s

o f t h e C2 m o le c u le seem ed e s p e c i a l l y s t r o n g w hen o r g a n ic s a m p le s p a s s e d
th e d e te c to r *
is o la te d

By m eans o f a g r e e n f i l t e r ,

fro m t h e s tr o n g s p e c t r a l l i n e s

th e y can be f a i r l y w e ll

o f a n y o f t h e common c a r r i e r

g ases used*
The e l e c t r i c a l p r o p e r t i e s
p o s s ib ilitie s
o f th e

f o r d e te c tio n

o f th e

g lo w d i s c h a r g e a l s o

o f s a m p le s *

s u g g e s te d

M e asu re m e n t o f t h e c o n d u c t i v i t y

g lo w d i s c h a r g e w a s a t t e m p t e d u s i n g a b r a s s t u b e a s o n e e l e c t r o d e

and a n i n n e r w ir e a s t h e

o th e r e le c tr o d e .

C u rre n t w as s u p p lie d b y a

b a t t e r y , and c h a n g e i n c u r r e n t flo w fro m t h e b a t t e r y th r o u g h t h e e l e c t r o d e s
i n t h e d i s c h a r g e w as m o n ito r e d w ith a ra ic ro a m m e te r*

I t w as f o u n d t h a t t h e

c u r r e n t d id in d e e d

ch an g e s t r o n g l y w hen a f o r e i g n

e le c tro d e re g io n .

I t w as a l s o fo u n d t h a t t h e b a t t e r y w as s u p e r f l u o u s .

The T e s la e x c i t e d

g lo w d i s c h a r g e b e c a m e p a r t i a l l y

a s y m m e tric a lly p la c e d e le c tr o d e s *

q u ite d iff e re n t*

re c tifie d

(6U)

in t h e i r ra d io fre q u e n c y d is ­

a l t h o u g h t h e i r m e th o d o f e x c i t a t i o n
T h e re a r e

o th e r re p o r ts

fro m a r a d i o f r e q u e n c y d i s c h a r g e
The s i g n a l d e p e n d s u pon th e

by th e

A s i m i l a r e f f e c t , a s m e n tio n e d e a r l i e r ,

h a s b e e n r e p o r t e d b y K a rm e n a n d Bowman
c h a rg e d e te c to r ,

g as p a s s e d th ro u g h th e

( 6 6 ,6 ? ) *

in th e

o f th e d is c h a rg e i s

lite ra tu re

of re c tific a tio n

and a T e s la s p a r k d is c h a r g e

a s y m m e tric a l l o c a t i o n

o f th e e le c tro d e s ,

(68).
and

86

must be a t tr ib u t e d t o p r e f e r e n t ia l capture o f e le c t r o n s a t th e more a c c e s s ­
i b l e c e n te r e le c t r o d e , w ith th e p o s i t iv e ion s becom ing d isch arged a t th e
o u ter j a c k e t .

The in n e r e le c tr o d e i s thus n e g a tiv e and th e ja c k e t i s

p o s i t i v e w ith r e s p e c t t o th e e x te r n a l c i r c u i t .
S in c e b oth th e p h otom etric means o f d e t e c t io n and th e e l e c t r i c a l or
T esla r e c t i f i c a t i o n means showed s im p lic it y o f d e sig n coupled w ith m inim al
ex p en se, i t was d ecid ed to pursue fu r th e r each o f th e s e forms o f s e n s in g
e le m e n ts .
D . E xperim ental
1 . R eagents
a . Compressed Gases
Gases used w ere th o se com m ercially a v a ila b le In s t e e l c y lin d e r s or
le c t u r e b o t t l e s , used w ith o u t p u r if i c a t io n .

The g ases and t h e i r minimum

p u r ity s p e c if i c a t i o n s are ta b u la te d belows
Gas
Argon
Helium
N itro g en
Oxygen
Hydrogen
Methane
Ethane
E th y len e
E th y len e oxide
A cety len e
Propane
Cyclopropane
1-But ene

P u r it y
(p e r c e n t)
99 -9 9 8
99-99
99-1
99- 6
99. 8
9 9 .0
9 5 -0
9 9 .5
9 9 .7
Tech
99- 0
99 -5
9 9 .0

87

A l l g a ses w ere o b tain ed from The Matheson Co. , I n c . , E ast R utherford ,
New J e r s e y , e x ce p t oxygen and a c e ty le n e ,w h ic h were su p p lied by th e
N a tio n a l C y lin d er Gas Company, C hicago, I l l i n o i s .
bo A ir
A ir was from th e la b o r a to r y atm osphere, d ried by p a ssin g through
two fiv e -h u n d red m i l l i l i t e r d ryin g tow ers o f anhydrous calcium s u l f a t e
( D r ie r it e ) « The a i r was f i l t e r e d a f t e r le a v in g th e d ry in g tower b y p a ssin g
through a one-hundred m i l l i l i t e r wad o f c l o s e ly packed Pyrex w o o l.
c . N a tu ra l Gas
N a tu ra l gas f o r th e sample chromatogram o f F igu re 16a was tak en
from th e c i t y m ain.

The a n a ly s is was fu rn ish ed by th e Consumers Power

Company o f L a n sin g , M ichigan.
d . O rganic L iquid Samples
Organic liq u id sam ples were A. C. S. rea g en t grade chemical s, used
w ith o u t p u r i f i c a t i o n .
2 o Apparatus
a . G eneral D esig n
The d isc h a r g e tu be p o r tio n o f t h e d e te c to r was sim p ly a g la s s
c a p illa r y tu b e ( 0 .5 mm» d iam eter) a tta ch ed d i r e c t l y to th e column e x i t .
A la b o r a to r y T e s la c o i l le a k t e s t e r provided th e sou rce o f e x c it a t io n o f
th e d isc h a r g e , which was tr a n sm itted through a p ie c e o f aluminum f o i l
connected t o th e higjh v o lt a g e probe te r m in a l (th e probe i t s e l f was removed
and th e aluminum f o i l in s e r te d in th e end o f th e le a k t e s t e r in p la c e o f

88

th e probe) and wrapped around th e c a p illa r y tu bin g*

A sm a ll d iam eter

w ire lod ged in th e c a p illa r y and ex ten d in g downstream from th e r e g io n
e n c ir c le d by th e aluminum f o i l served as a low work fu n c tio n source o f
e le c t r o n s and s t a b i l i z e d th e d isc h a r g e , which oth erw ise would have needed
t o depend f o r i n i t i a t i o n upon more d i f f i c u l t rem oval o f e le c tr o n s from
th e g la s s w a lls *
The d isc h a r g e occurred downstream from th e end o f th e in s e r te d w ire
t o a r e g io n n ea rer ground p o t e n tia l*

A s im ila r ^ e le c tr o d e le s s e le c t r o d e 11

can se r v e as th e ground, by in s e r t in g another f r e e p ie c e o f w ir e in th e
c a p i l l a r y and surrounding th e reg io n o f th e c a p illa r y c o n ta in in g th e
w ire b y a grounded p ie c e o f aluminum f o i l *

A b e t t e r ground can be prepared

by a tta c h in g th e c a p illa r y t o a grounded m etal tu b in g co n n ecto r, u sin g
itqh.„r in g s e a ls *

For th e d i r e c t cu rren t measurement, a b ra ss t e e -t u b e

con n ector can c o n v e n ie n tly be u sed .
connected

The d isch a rg e c a p illa r y tu b e was

t o one arm of th e te e -tu b e ; an in n er e le c tr o d e was mounted in

g la s s and connected t o th e o p p o site arm

o f th e t e e - t u b e , w ith th e in n er

e le c t r o d e

ex ten d in g w ith in th e te e -tu b e v e r y n e a r ly t o th e end o f

d isc h a r g e

c a p illa r y tu bej th e th ir d arm

th e

o f th e t e e -t u b e con tain ed th e

e x i t tu b e , which could be ven ted t o th e atmosphere or could lea d t o a
manometer, flo w c o n tr o l v a lv e , b a l l a s t f l a s k , and vacuum pump or w ater
a s p ir a to r *

The in n er e le c t r o d e was connected to ground, and th e body o f

th e t e e - t u b e served as th e oth er e le c tr o d e fo r th e d ir e c t cu rren t
measurement *
The experim ents u sin g th e T e sla e x c ite d glow d isch a rg e as th e b a s is
f o r a gas chrom atographic d e te c to r in volved two b a s i c a l l y d if f e r e n t k in d s

89

o f s e n s in g elem en ts“--"photometric and e l e c t r i c a l .

I t proved more con­

v e n ie n t <, e x p e r im e n ta lly , t o c o n str u c t one d isc h a r g e e x c i t e r tube and
in c o r p o r a te b oth s e n s in g elem en ts in to th e d e s ig n .

The s e n sin g elem en ts,

■which cou ld be m onitored s in g ly or sim u lta n e o u sly , need be in no way
in te r d e p e n d e n t, e x c ep t as a m atter o f co n v en ien ce.

For t h i s r ea so n , th e

c o n s tr u c tio n o f th e s e d e te c to r s w i l l be d escrib e d more or l e s s co n cu rren tly
in th e same manner as th e y were developed in th e la b o r a to r y .
bo D e te c to r C o n stru ctio n
(l)

M echanical D e t a il o f S en sin g E lem ents.

d e t e c to r used i s sk etch ed t o f u l l s c a le in Figure 5•

The f i n a l form o f
The e l e c t r i c a l

s e n sin g elem ent c o n s is te d o f a standard q u a rte r -in c h f la r e - t y p e b r a ss
tu b in g t e e which had been reamed out to £.95> mm. (15/6H i n . ) .

This t e e

served as th e p o s i t i v e e le c tr o d e in th e e l e c t r i c a l s e n sin g elem ent and
was connected t o an e l e c t r i c a l c i r c u i t by a s h ie ld e d conductor a tta ch ed
t o th e t e e w ith an a l l i g a t o r c l i p .

The f la r e - s e a t in g sh ou ld ers in th e

t e e w ere m ille d o f f and th e f l a r e on the hexagon al nut on th e low er arm
o f th e t e e was m ille d away t o th e minimal th ic k n e s s which did not en large
th e in n e r diam eter o f th e n u t.

The oth er elem ents o f th e d e te c to r flo w

system were connected t o th e t e e u sin g Pyrex tu b in g and l/l^ - in . i . d . ,
3 /8 -in o o.do, s i l i c o n e rubber wQtt r in g s which se a te d a g a in st th e f l a t
ends o f t h e t e e .
An in n er e le c tr o d e was made from a l / 8 - i n . d iam eter bronze b ra zin g
ro d , 15 cm. lo n g , which was ground o f f f l a t on th e end which en tered th e
s y ste m .

The rod was s e a le d w ith a sm a ll amount of A piezon W 1 wax in t o a

90

<a

SILICONE RUBBER
“O' RING

LEAD TO ELECTRICAL
DETECTO R CIRCUIT
MANOMETER,
F L O W LIM ITING
V A L V E , BALLAST
FLASK, PUM P

ic m ^

LEADS T
O PH O TO M ET R IC
DETECTOR CIRCUIT

£

-K

o
oo

T E S L A C O IL
SECONDARY
rv.

\f

£
o

-1 f

COLUMN
FIGURE 5 .

OR F L O W L IM IT E R
EFFLUENT

T E S L A DISC H A R G E D E T E C T O R FOR G A S
CHROMATOGRAPHY.
(F U L L SC A LE)

91

13 cm. le n g th o f P yrex tu b in g which was n om in ally 6 mm. o . d . , b u t measured
5 -75 mm*

The rod was a snug f i t in to th e g la s s tu b e, so th a t s e a lin g w ith

wax was e a s i l y done w ith a minimum o f wax.
b oth ends t o g iv e r i g i d i t y .

The rod was w a x -sea led a t

The end o f th e rod which was ground o f f f l a t

was l e f t t o p ro tru d e 5 mm- from th e end o f th e g la s s tu b e .

This e le c t r o d e

was p la ce d in th e upper arm o f th e t e e u sin g an ,,0I* r in g s e a l .

I t was

in s e r te d so t h a t th e sh o r t p ro tru d in g end o f th e b r a z in g rod came t o r e s t
about U mm. from th e lowerm ost dim ension o f th e low er h exagon al nut when
th e n u ts were s e a te d a g a in s t th e r in g s .

The ^O11 r in g s e a ls allow ed move­

ment o f th e e le c tr o d e even a f t e r vacuum was a p p lied t o th e t e e , so t h i s
adjustm ent could be v a r ie d w h ile o p era tin g th e d e t e c t o r .

The oth er end

o f t h i s e le c tr o d e was clamped fir m ly and connected t o a good ground.
An 8 mm. le n g th o f th e same s i z e Pyrex tu b in g as used t o co n ta in th e
in n er e le c t r o d e was in s e r te d in th e c en ter arm o f th e t e e as f a r as i t
would go w ith th e in n er e le c t r o d e in p o s it io n , and th en withdrawn a f r a c t io n
o f a m illim e te r so t h a t i t did not touch th e o th er tu b in g .

This g la s s arm

from th e t e e was th en connected v i a rubber tu b in g t o th e s id e o f th e flo w
system c o n ta in in g a mercury manometer, 0 -5 mm. range McLeod gauge, Hoke
diaphragm f lo w - lim it in g v a lv e , o n e - l i t e r b a l l a s t f l a s k , and vacuum pump.
In th e e a r ly p a rt o f th e exp erim en tal work, some measurements were
made u s in g a s l i g h t l y sm a lle r b r a ss t e e and a l / l 6 - i n . b r a z in g ro d .

This

t e e was 1 5 / l 6 i n . h igh and had a k mm. in n er diam eter which was reamed
out on th e ends t o a d iam eter o f 6 .3 5
reamed t o a depth o f 7 mm.

(l/h in .) .

The ends were

The hexagonal n u ts were 1 .1 cm. ( 7 /1 6 i n . ) in

th e d ir e c t io n o f th e thread and were n ot a lt e r e d .
from s id e t o s id e on th e hexagon.

The nu ts were l / 2 in .

92

The co n n ectin g g la s s tu b es p la ced in th e arms o f th e t e e were th e
same as p r e v io u s ly d e sc r ib e d *

The tube w ith th e in n er e le c tr o d e had t o

be reduced in d iam eter t o make a snug f i t t o th e l / l 6 - i n . b ra zin g ro d .
This e le c t r o d e protruded 1 .9 mm. so th a t th e end could b e made t o tou ch
th e end o f th e c a p illa r y tube, which was se a te d th e f u l l 7 mm. in to th e
te e .

B e s id e s th e s i z e o f th e t e e and inn er e le c t r o d e , t h i s arrangement

had a la r g e r dead volume w it h in th e t e e , s in c e th e in n er e le c tr o d e was
unsheathed f o r 18-19 mm. in s id e th e t e e .

T his volume d id n ot n o t ic e a b ly

a f f e c t th e sample band sh a p es, s in c e e v id e n tly th e space betw een th e end
o f th e e le c t r o d e and th e end o f th e c a p illa r y i s where s ig n i f i c a n t
a lt e r a t io n s o f cu rren t o ccu r.

The space p a s t th e end o f th e e le c tr o d e

towards th e e x i t arm o f th e t e e must c o n tr ib u te l i t t l e curren t t o th e
d is c h a r g e .
Measurements made w ith t h is s e n sin g elem ent are la b e le d as made
w ith th e l / l 6 - i n . e le c t r o d e .
(2 )

E x c ite r Tube.

The low er arm o f th e t e e was connected t o th e

sam pling s id e o f th e flo w system through th e e x c it e r tu b e .

The e x c it e r

tu b e was a 25 cm. le n g th o f 0 .5 mm. i . d . Pyrex c a p illa r y tu b in g which
had an e x t e r n a l d iam eter o f 5<>75 mm.

A p ie c e o f w ir e c o n s is t in g o f two

stra n d s o f Mo. 3h p latin u m w ir e tw is te d t o g e th e r , h avin g an 8 cm. f i n a l
le n g th ,w a s in s e r te d e n t i r e l y in t o th e c a p illa r y tu b e .

The end o f th e

w ire n e a r e s t t h e d e t e c t o r was 2 .9 cm. from t h e end pf t h e tu b in g .

The

w ir e was s u f f i c i e n t l y kinked so t h a t i t could not be moved e a s i l y i n
t h e tu b e .

93

The o u ts id e o f th e c a p illa r y tube was wrapped w ith aluminum f o i l
b e g in n in g £ mm. upstream from th e upper end o f th e platinu m w ir e and
e x ten d in g 8 cm o i n t h a t d ir e c t io n * The aluminum f o i l was a d ou ble th ic k ­
n e s s fo ld e d t o 8 cm. s q u a r e .

The aluminum f o i l on th e tu be was wrapped

w ith s e v e r a l la y e r s o f S co tch e l e c t r i c a l ta p e , ex cep t f o r a sm a ll a rea in
th e c e n te r th rough which an aluminum s t r i p which e n c ir c le d th e aluminum
w rapping p assed f o r c o n n ectio n t o th e secondary o f th e T e sla c o i l .

The

d isc h a r g e from t h e T e sla c o i l was coupled from th e aluminum f o i l t o th e
in t e r n a l p latin u m w ir e c a p a c i t iv e ly .

The gas in th e c a p illa r y tube

formed a glow from around th e end o f th e w ire t o th e in n er grounded
e le c t r o d e o f th e b r a s s t e e j o i n t .

The in t e r n a l w ire g r e a t ly in c r e a se d

th e s t a b i l i t y o f th e d is c h a r g e .
The e x c i t e r tu b e was in s e r te d as s h a llo w ly as p o s s ib le in t o t h e t e e
and y e t s e a l s e c u r e ly w ith th e tt0u r in g .

This req u ired 3 mm. in s e r t io n

i n t o th e t e e , measured from th e bottom o f th e h exagonal n u t.

The in n er

e le c t r o d e and c a p illa r y end were th en ap proxim ately 1 mm. a p a rt.
For p h otom etric m easurem ents, a C la ir e x cadmium s u lf id e or cadmium
s e le n id e (CL-2 or GL~3) p h otocondu ctin g c e l l was in s e r te d in to a p ie c e
o f rubber tu b in g which was a snug f i t and th e tu b in g taped t o th e e x c it e r
tu b e j u s t below th e t e e .

The p h o to c e ll was l e f t l / k i n . from co n ta c t

w ith th e g la s s tu b in g to in s u la t e i t e l e c t r i c a l l y from th e d isch a r g e tu b e .
A W ratten g e l a t i n f i l t e r was in some c a se s attach ed t o th e p h o t o c e ll.
T his was done by c u ttin g a small, p ie c e o f th e f i l t e r th e same diam eter
as t h e p h o t o c e ll and cem enting th e f i l t e r w ith G ly p ta l l i g h t l y around th e
edge t o ' th e end o f th e p h o t o c e ll.

The c e l l and f i l t e r were th e n in s e r te d

9h

i n rubber tu b in g as d esc r ib e d above„ A W ratten No. 7b green f i l t e r was
used t o i s o l a t e th e C2 spectrum em itted by organ ic m olecu les in th e
d isch a r g e e
(3 ) E l e c t r i c a l C i r c u i t s .

(a ) G eneral.

The e l e c t r i c a l c i r c u i t s

employed w ith th e T e s la d isc h a r g e gas chromatography d e te c to r a re d e p ic te d
s c h e m a tic a lly i n F ig u re 6 .

R e s ista n c e and ca p a c ita n c e v a lu e s have a manu­

f a c t u r e r ' s t o le r a n c e o f tw en ty p e r c e n t.

The v a r ia b le b a t t e r i e s were fo u r

B urgess No. 5 1 5 6 , 22 1 / 2 -V . b a t t e r ie s connected in s e r i e s .

These b a t t e r ie s

had many ta p s on them, so t h a t a grea t v a r ie t y o f v o lta g e s betw een 0 and
± 90 V. could be o b ta in e d .

The lo w e st v o lta g e p o s s ib le was 1 1 /2 V.

The c i r c u i t s a re shown w ith th e s w itc h e s in th e p o s it io n s most fr e q u e n tly
u se d .
O c c a s io n a lly i t was d e s ir e d to s h i f t th e m eter b a s e li n e .
cu rren t b ia s in g c i r c u i t was th e n sw itched in by s w itc h , SB.

A low
T his c i r c u i t ,

c o n s is t e d o f a s tu d e n t p o ten tio m eter c i r c u i t , P , i s o l a t e d from th e m eter
by a 0 .2 megohm r e s i s t o r .

T his c i r c u i t was capable o f fu r n is h in g b ia s in g

c u r re n ts in th e range o f 0 -1 5 microamperes to th e m eter.

The cu rren t

p a s s in g through th e t e e j o i n t d e t e c to r c e l l from t h is sou rce was m in is c u le
b ecau se o f th e h ig h impedance o f th a t branch o f th e c i r c u i t ,
(b )

E l e c t r i c a l D e t e c t o r . The e l e c t r i c a l d e t e c to r in F igu re 6A c o n s is t s

b a s i c a l l y o f two s e n s in g e le c t r o d e s which are in co n ta ct w ith t h e T e sla
d is c h a r g e .

There i s a n e t r e c t i f i c a t i o n o f th e T esla d isc h a r g e cu rrent

caused by th e asym m etrical lo c a t io n o f th e two e le c tr o d e s in th e d is c h a r g e .
The in n er e le c t r o d e , which i s more a c c e s s ib le t o th e io n stream em erging
from th e c a p i l l a r y tu b e , c o l l e c t s e le c t r o n s p r e f e r e n t i a l l y , and so i s

95

i Met;

ST f
B

rfc

!00K

0-90V

+ <>

2aF

.....

BRASS "T"

CIRCUIT FOR

sc\
mr
— 0-90V

A \-

0-140 41

eoov
-

i(

^

> 15041
* f P
^ :3 v

SS
sm?
6 0 0 v'

A.

r

SB

^STftOHFC

ELECTRICAL

200 K
-w w — ^

DETECTOR.

a aa / v—

-W W W

L V 2eoK
inf
600 V

c
CdU

-n r

Ijuf
Q 9 nV

CdSI

600V

or

B, AND

FbURE 6,

D

H CTOM ETRIC

C.
D E T E C T O R CIRCUi

ELECTRICAL CIRCUITS USED W I T H TESLA D I S o H A K S c
DETECTOR FOR GAS C H R O M A T O G R A P H Y ,

96

th e so u rce of* a d i r e c t cu rren t which flo w s from t h i s e le c tr o d e through
th e cu rren t loop c o n ta in in g th e f o llo w in g components..

Two o n e -m illih e n r y

ra d io fr eq u e n c y chokes w ere used t o b lo ck ra d io freq u en cy v o lt a g e s from
th e m eterin g d ev ic e* A.

The meter was a reco rd in g microammeter used in

th e ranges co v e rin g 0 -5 5 0 microamps.

The reco rd er was a F is h e r R e c o r d a ll,

h avin g th e ran ges 0-5*5* 0 - 1 1 .0 microamps* and decade m u lt ip lie r s o f
th e s e scales*.

An a d d it io n a l s c a le o f 0-22 microamps, was added by

a p p ro p ria te sh u n tin g o f th e 0 -1 1 m icro amp 0 in p u t.

The v o lta g e drop a c r o s s

th e microammeter a t f u l l s c a le d e f le c t io n was 5*5 m i l l i v o l t s .

The one —

megohm and 0.1-megohm r e s i s t o r s in t h is s e r i e s loop were cu rren t lim it e r s
or s e n s i t i v i t y s e l e c t o r s .

The

one-megohm r e s i s t o r was norm ally in th e

c i r c u i t , and th e sm a lle r r e s i s t o r could be sw itch ed a cr o ss th e h ig h er
r e s i s t o r u s in g sw itch S S .

The sm a ller r e s is t a n c e in crea sed th e cu rren t

by a f a c t o r o f ap p roxim ately 10 b u t v a r ie d w ith th e c o n d u c tiv ity o f th e
d isc h a r g e ( c f . T able V T H ).

The b a ttery * B, was not n orm ally in th e

c ir c u it * bu t could be used as a source o f b ia s f o r red u cin g th e background
cu rren t in th e d e t e c t o r .

The c a p a c ito r s a cr o ss th e m eter c i r c u i t served

t o b yp ass ra d io freq u e n c y v o lt a g e s from th e m eter and t o smooth out n o is e .
N orm ally th e 2-m icrofarad condenser was used w ith th e one-megohm r e s isto r *
g iv in g a tim e c o n sta n t o f ap p roxim ately two se c o n d s.

When th e more

s e n s i t i v e s c a le was used* i t was u s u a lly when th e n o is e l e v e l was v e r y
low* and th en th e 2-m icrofarad condenser was a ls o used* g iv in g a tim e
co n sta n t o f a p p roxim ately 0 .2 seco n d s.

In some cases* however* th e 8 -

m icrofarad condenser was sw itch ed in a lso * g iv in g a 2 - s e c . tim e co n sta n t
on th e h ig h s e n s i t i v i t y ra n g e.

91

The resp o n se o f t h i s d e t e c to r has a ls o been m onitored on a p o t e n t i­
om eter ( 0 - 501 rov o f u l l s c a le ) by r e p la c in g th e microammeter w ith a r e s i s t o r
o f a few thousand ohms and p la c in g th e p o ten tio m eter a cro ss i t .
The output h as been m onitored on sim p le n on -record in g microammeters
and v o lt m e t e r s * Such m eters could serv e e a s i l y f o r d em on stration p u rp oses
or m on itorin g p r e p a r a tiv e chrom atographic columns*
(c)

P h o to m etric D etecto r*

The p hotom etric d e te c to r c i r c u i t s in

F ig u re 6B and 6C, c o n s is t v e r y sim p ly o f a G la ir e x p h otocond u ctin g c e l l ,
a sou rce o f p o t e n tia l,a n d a meter*

F igu re 633 was th e c i r c u i t used in

r ec o r d in g th e r e sp o n se , where th e metei> A, was a g a in th e F ish e r R e c o r d a ll.
F ig u re 6C i l l u s t r a t e s th e u se o f a sim ple v o ltm e te r to m onitor th e resp o n se
o f th e d e te c to r *

The f i l t e r condensers in b oth c ir c u it s norm ally were

n ot n e c e s s a r y , s in c e th e p h o t o c e lls generated or picked up v ery l i t t l e
o b serv a b le n o is e .

Norm ally a p o t e n t ia l o f 90 v o l t s or l e s s was a p p lie d ,

alth ou gh t h e m anufacturer s p e c i f i e s th a t 300 V* may be used w ith G la irex
C3>2 and GL-3 p h o to c e lls * The cadmium s u lf id e , GL-2, p h o t o c e ll, which i s
s e n s i t i v e t o v i s i b l e l i g h t , i s s p e c if ie d t o produce a 100-raicroamp. s ig n a l
w ith a 100 V* a p p lied when i t r e c e iv e s an illu m in a tio n o f 2 f o o t candle s .
The cadmium s e le n id e , CL-3, p h o t o c e ll, which i s red s e n s i t i v e , i s s p e c if ie d
t o produce a 600-microamp * s ig n a l w ith 100 V* a p p lied when i t r e c e iv e s a
s im ila r illu m in a tio n *
c* The Flow System
(1 )

General*

F ig u re 7 shows s c h e m a tic a lly th e flo w system used w ith

th e d e t e c t o r s d esc rib e d above*

C arrier gas from a c y lin d e r w ith a

SYSTEM

ZD

Q_
cc
<C
o

CO

o

DISCHARGE

Q_

cc

USED
WITH
TESLA
DISCHARGE DETECTOR.

<

LLJ

cc

EXCITED

C_D

CL

o

CD

FLOW

CO

FIGURE 7.

GLCW

98

cc

o

99

p r e ssu r e red u cin g v a l v e , or in th e case o f a i r , from a d ry in g tu b e , was
in tro d u ced through a o n e - l i t e r b a l l a s t f l a s k , B .

The gas was conducted

through t h r e e f e e t o f 8 - mm* Pyrex tu b in g t o th e sample i n j e c t i o n r e g io n .
The sam ples w ere in j e c t e d through th e q u arter—in ch s e c t io n o f p ressu re
tu b in g , I , w hich was 3 / l 6 i n .

i . d . w ith a 3 / l 6 - i n . w a l l .

T his rubber

i n j e c t i o n s e c t i o n was backed by a 5 ~ in . le n g th o f 0 .5 mm. i . d . c a p illa r y
tu b in g , Ro

The gas flaw ed through th e Perk in-E lm er typ e B, s i x - f o o t ,

l / U - i n . d iam eter, packed chrom atographic column, C, th en through th e
d e t e c t o r , c o n s is t in g o f e x c it e r tu b e , E, T e sla c o i l , TC, p h o t o c e ll, PC,
and t e e j o i n t , T, which was d e p ic te d more f u l l y in F igu re i |.

The gas

p assed out through a o n e - l i t e r b a l l a s t f la s k and a Welch B u o -se a l mechani­
c a l pump.

P r e ssu r e was measured w ith an open-end manometer, M, and w ith

th e 0 -5 mm. McLeod gauge, G.

The pumping r a t e could be c o n tr o lle d by

r e g u la t in g th e Hoke diaphragm v a lv e , H.
th e atm osphere through stop cock SA.

The d e te c to r could be ven ted t o

Components in th e system were con­

n ected w ith th e s i z e p r e ssu r e tu b in g d escrib ed above, w ith th e components
b e in g pushed in t o c o n t a c t.
(2 )

O p e r a t i o n W i t h o u t a C h r o m a t o g r a p h i c C o lu m n .

d e te c to r re s p o n s e a lo n e , th e
(C , I ,

F o r s tu d y o f th e

c h r o m a t o g r a p h i c c o lu m n a n d i n j e c t i o n s y s t e m ,

and R) w e re r e p l a c e d b y a f lo w l i m i t e r , b a c k e d b y a t h r e e - i n c h

s e c tio n
s e c tio n .

o f th e 3 / l 6 - i n . ru b b e r p r e s s u r e tu b in g to b e u se d as th e i n je c ti o n
The flo w

tu b in g b y in s e r tin g
o f th e tu b in g .

l i m i t e r w a s c o n s t r u c t e d f r o m 0 .5 mm. i . d .

c a p illa ry

a f e w c e n t i m e t e r s o f N o . 25 w i r e i n t o t h e u p s t r e a m e n d

The p r e s s u r e d ro p a c r o s s t h i s

b y v a ry in g th e le n g th o f w ire in s e r te d .

l i m i t e r c o u ld b e a d j u s t e d

100

(3 )

Oxygen S ca v en g er.

With argon c a r r ie r i t was found d e s ir a b le t o

in tro d u ce a c o n t r o lle d slow flo w o f oxygen gas through a t e e tube in t o
th e c a r r ie r -sa m p le stream j u s t b e fo r e th e p o in t o f e x c it a t io n o f th e d i s ­
chargee

The t e e tu be was formed from 0 .5~nime c a p illa r y tu b in g and

in s e r te d i n th e flo w system a t p o in ty 0 , in F igu re 7*
t e e i n th e c a r r ie r l i n e was 2 .5 i n . lo n g .

The segment o f th e

The branch i n th e t e e was

connected t o a tw o -fo o t segment o f 0*5—mm. c a p illa r y t u b in g ,in t o which
No. 25 w ir e had b een in s e r te d th e f u l l le n g th t o l i m i t th e flo w o f oxygen.
The oxygen was su p p lie d from a c y lin d e r equipped w ith a red u cin g v a lv e and
n e e d le v a lv e * The oxygen flo w was c o n tr o lle d w ith th e n e e d le v a l v e .

The

flo w r a t e o f oxygen used was v e r y low* e s s e n t i a l l y j u s t lea k a g e through
th e s e a te d n e e d le v a lv e *
The oxygen removed f r e e r a d ic a l fragm ents t o p reven t t a i l i n g and
f a u l t y band shap es r e s u lt i n g from contam in ation o f th e d isch a rg e tube and
e le c t r o d e s w ith carbonaceous breakdown p ro d u cts.
3 o E xp erim en tal Procedure
a . G eneral D e t a ils
( 1 ) Sam pling te c h n iq u e s .

In stu d y in g th e resp on se o f th e d e te c to r

alone* w ith o u t a chrom atographic column in th e system* fo u r b a s i c a l l y
d i f f e r e n t sam pling te c h n iq u e s were em ployed.

A ll samples in je c te d were

gaseou s and in j e c t e d w ith hypodermic sy r in g e s u s in g No. 27 n e e d le s .
S im p le i n j e c t i o n s in measured amounts were lim ite d t o 0 .0 1 —m l.
sam ples s in c e t h i s was th e s m a lle s t grad u ation on th e s m a lle s t (0 .2 5 m l.)
s y r in g e a v a ila b le a t th e t im e .

101

S m a l l e r s a m p le s i z e s
te c h n iq u e o
s lig h tly

c o u l d b e m ade b y u s i n g a s t r e a m - s p l i t t i n g

T h is w as d o n e i n t h e c a s e o f a rg o n c a r r i e r w h ic h w as a t

ab o v e a tm o s p h e ric p r e s s u r e

r e a d i l y a c c o m p lis h e d b y i n s e r t i o n
in to

a s e c tio n

s p littin g

s p l i t th e

In o rd er to

c o m in g i n t o

T he s t r e a m ~
The o n ly

1 , w h ic h w a s a c h i e v e d u s i n g a N o . 20

s tr e a m .

d e te rm in e th e d e te c to r re s p o n s e f o r a p a r t i c u l a r co n cen ­

o f s a m p le v a p o r i n t h e c a r r i e r gas*

o f th e d e s ire d

s e c tio n .

c o u ld b e v a r i e d b y a l t e r i n g t h e n e e d le s i z e .

r a t i o u s e d w a s a p p r o x i m a t e l y 12 t o

tra tio n

s p l i t t i n g w as

o f a s u i t a b l y s i z e d h y p o d e rm ic n e e d le

o f ru b b e r tu b in g a f t e r th e in je c ti o n

ra tio

n e e d le t o

o n ly , a n d t h e r e f o r e t h e

c o n c e n tr a tio n w e re u s e d .

la rg e

in je c tio n s

o f s o lu tio n s

I t w as fo u n d t h a t w ith a i r

c a rrie r

t h e i n j e c t i o n s y s te m a t a tm o s p h e r ic p r e s s u r e , a r e p r o d u c i b l e

tr a p e z o id a l re s p o n s e p a tt e r n w ith v e ry s te e p

le a d in g and t r a i l i n g

edges

c o u ld b e o b ta in e d w i t h t h e e l e c t r i c a l d e t e c t o r u s i n g a 2 0 - m l. i n j e c t i o n .
T h is s i z e

i n j e c t i o n w as a d e q u a te t o d i s p l a c e t h e a i r

i n t h e t u b i n g , fo rm in g a lo n g s lu g o f th e
re sp o n se p a tte r n j u s t d e s c rib e d .

gave th e

i t w as fo u n d

o b ta in re p ro d u c ib le

b e c a u s e t h e a r g o n cam e i n t o t h e i n j e c t i o n
5

s a m p le s o l u t i o n w h ic h

W it h a r g o n c a r r i e r ,

n e c e s s a r y t o u s e 5 > 0-m l. s a m p l e s , t o

c a r r i e r b a c k u p s tre a m

in je c tio n p a tte rn s ,

s e c tio n a t a p re ssu re

of about

P .S . l o g o

In al 1 c a se s b u t one, th e
t h e h y p o d e rm ic s y r i n g e s .
th e t i p ,

in

T h e 2 0 - m l . s y r i n g e u s e d h a d a d e a d v o lu m e i n

in c lu d in g th e n e e d le ,

s y r in g e w as 0 .7 m l.

g a s e o u s s o l u t i o n s w e r e m ade u p d i r e c t l y

o f 0 .3 m l., w h ile t h a t f o r th e £ 0 -m l.

The c o n c e n t r a t io n s

c o r r e c t i n g f o r t h e s e d e a d v o lu m e s .

of th e

s o lu t i o n s w ere c a lc u la te d

M ix in g w a s a s s u r e d b y s e a l i n g t h e

102

n e e d le t>ip o f th e sy r in g e in a rubber sto p p er and ‘•pumping11 on th e
s y r in g e s e v e r a l t im e s *
For th e stu d y o f d e te c to r resp onse to methane in argon, a sto ck
s o lu t io n o f 1*83 volume p ercen t methane was prepared and d ilu t io n s made
from t h a t s t o c k * The s o lu t io n was sto red a t a p ressu re above atm ospheric
t o p r ev en t p o s s ib le a i r contam ination*
Sam ples o f argon sa tu r a te d w ith organic vapors were obtained by
b u b b lin g argon through a gas w ashing b o t t l e h avin g a s in te r e d g la s s
b u b b ler immersed in th e liq u id o f in t e r e s t *

The vapor p ressu re was regu­

la te d by imm ersing th e w ashing b o t t l e in a c o o lin g bath*

Benzene and

cycloh exan e w ere used t o s a tu r a te argon gas a t t h e i r f r e e z in g p o in ts*
A cetone was u sed a t 0°C * The c o n cen tra tio n o f th e vapors in th e argon
were estim a ted u sin g th e vapor p r essu res o f th e s e su b stan ces a t th e s e
tem p era tu res, u sin g v a lu e s l i s t e d b y Jordan (59)*
(2 } P r essu re and Flew Rate*

To stu d y th e d e te c to r resp on se w ith o u t

th e chrom atographic column, th e column was rep laced a t p o in t C in F igu re
7 b y a f lo w - lim it in g c a p illa r y as d escrib ed in th e apparatus se c tio n *
The p r e ssu r e drop a c r o ss th e c a p illa r y was ad ju sted by th e len g th o f w ire
in s e r te d in th e c a p i l l a r y so t h a t i t was comparable to t h a t o f th e s i x f o o t packed column employed*

In th e runs made w ith th e d e te c to r u sin g

th e l / l 6 “ in * in n er e le c t r o d e , w ith a c a r r ie r gas a t atm ospheric p r e s su r e ,
t h i s p r e ssu r e drop was such t h a t th e p ressu re in th e d e te c to r sy stem ,
when th e flo w c o n tr o l v a lv e , H, was wide open,was in th e range 3~U ram.
Subsequent runs u sin g th e l / 8 - i n * in n er e le c tr o d e t e e were a t a p ressu re
o f 2-3 mm*

This d if f e r e n c e was b ecause o f a le a k in th e system in th e

U03

v i c i n i t y o f th e vacuum pumpo

When a compressed c a r r ie r gas was used a t

a p r e ssu r e o f 5 poSoiogo behind th e flow l i m i t e r , th e p ressu re in th e
system in c re a se d ap p roxim ately 0 o$ mm»

The approximate flo w r a te as

estim a ted from th e le n g th o f tim e req uired f o r a 20 ml*, sample t o flo w
through th e d e t e c to r was 22 m l. per minute f o r a ir c a r r ie r a t atm ospheric
p re ssu r e and i;2 m lc per minute f o r argon c a r r ie r a t 5 p .S o i.g *

The r a te

o f flo w o f d isca rd ed gas in s t r e a m - s p lit t in g experim ents was measured by
d eterm in in g th e r a t e a t which i t f i l l e d a 50“ml*- sy r in g e having a f r e e l y
moving piston*.

Measurements made as a .fu n ction of p ressu re were accomp-

lis h e d by r e g u la t io n o f th e pumping r a te w ith diaphragm v a lv e , H*.
(3 )

Chromatograms *

I n ta c t as in F igu re 7°

For chrom atographic work, th e system was used

An argon p ressu re o f 10 p 0s . i » g . was used w ith a

slow oxygen flo w b led in a t a t e e below th e e x c i t e r »
b <> Procedure in U sing th e Photom etric D etecto r
The p h otom etric o b se rv a tio n s were made w ith a p h o t o c e ll in p o s it io n
on th e e x c i t e r tu b e below th e b r a ss t e e as d e p icte d in F ig u re % w ith a
f lo w - lim it in g c a p illa r y s u b s titu te d f o r th e chrom atographic column*.
The d isc h a r g e was a d ju sted as d escrib e d below under th e procedure in u sin g
e l e c t r i c a l d e t e c to r *.
Co Procedure in U sing th e E l e c t r i c a l D etecto r * A fte r th e system
was purged w ith th e c a r r ie r gas to be u sed , th e T e s la c o i l e x c it e r was
turned on.

The spark gap in th e T esla c o i l primary was a d ju sted t o g iv e

a l e v e l o f ou tpu t v o lta g e so th a t th e d isch a rg e e x c ite d in th e evacuated
tu b e was s t a b l e , but n o t so high as t o cause str o n g corona form ation

io u

about th e e x c i t e r tu b e .

The e l e c t r i c a l d e te c to r c i r c u i t o f F igu re 6A was

connected up w ith th e one—megohm s e r i e s r e s i s t o r and th e 2-m icrofarad
f i l t e r condensero

No e x te r n a l "voltage was ap plied.,

The cu rrent l e v e l as

measured on th e microammeter record er could be ad ju sted by moving th e
in n er e le c tr o d e (which was a t ground p o t e n t ia l) up and down in i t s s e a t
in th e t e e tu b e .

There was v e r y l i t t l e l a t e r a l p la y , b u t th e e le c tr o d e

could be moved r e a d ily i n th e v e r t i c a l d ir e c t io n , s lip p in g through th e
110W r in g s e a lo

In p r a c t ic e , r o t a tio n o f th e e le c tr o d e a ls o had a profound

e f f e c t on th e cu rren t in th e d e t e c t o r .

This was presumed t o be because

th e e le c t r o d e s were n ot m ic r o s c o p ic a lly sym m etrical, nor was th e in n er
e le c t r o d e e x a c t ly square on th e end in r e la t io n t o th e ca rrier-sa m p le
stream em erging from th e end o f th e c a p illa r y e x c it e r tu b e .

T h erefore,

th e r e were u n d ou b ted ly p re fe r r e d p o r tio n s o f th e e le c tr o d e which ca rried
th e cu rren t from th e glow d isc h a r g e .

By a d ju s tin g th e in n er e le c t r o d e ,

a minimum cu rren t was o b ta in e d , w h ile k eep in g th e end o f th e e le c tr o d e in
a r e g io n w ith in about one m illim e te r from th e end o f th e c a p illa r y e x c it e r
tu b e .

With t h i s minimum in th e cu rren t, th e r e a ls o occurred a minimal

n o is e l e v e l w ith o u t a p p re cia b le lo s s o f resp on se o f th e d e te c to r t o sample
vapors o

Table 7 shows th e approxim ate v a lu e s ob tain ed fo r t h i s minim al

cu rren t and n o is e l e v e l in v a r io u s c a r r ie r gases used w ith th e 1 / 16~and
1 /8 - i n . e le c t r o d e , to g e th e r w ith th e resp on se o f th e d e te c to r t o a 0 .0 1 m l. i n j e c t i o n o f m ethane.
When argon c a r r ie r gas was used w ith an oxygen scaven ger b le e d ,
a s l i g h t l y a lte r e d procedure was used to s e t up th e sy stem .

The system

was a d ju sted as d e sc r ib e d in th e p reced in g paragraph w ith th e oxygen

105

n eed le v a lv e c lo se d v e r y firm ly,,

The v a lv e was th en cracked a v ery s l i g h t

amount, and th e resp o n se current o f th e d e te c to r n o ted .
cu rren t in c r e a se d w ith th e added oxygen.

The d e te c to r

The cu rrent was allow ed t o in c r e a s e

ap p roxim ately te n microamperes on th e 0.1-megohra s c a l e .

This r e s u lte d in

a str o n g in c r e a s e in th e n o is e l e v e l on th e background c u r r e n t.

The in n e r

e le c tr o d e was r e a d ju sted by r o t a t io n or r a is in g , or b o th , t o reduce th e
cu rren t t o a p p roxim ately th e s t a r t in g l e v e l .

The e f f e c t iv e n e s s o f th e

oxygen i n k eep in g th e e x c it e r w ire and th e se n sin g e le c tr o d e s from p ic k in g
up carbonaceous m atter, which r e s u lt s in t a i l i n g of sample bands, was
checked by in j e c t in g in c r e a s in g ly la r g e r sam ples o f methane in to th e system .
The d e t e c to r was a b le t o handle a 0 .2 m l. in j e c t io n and retu rn sm oothly
t o th e b a s e li n e .

In th e absence o f th e oxygen, th ere was a tendency

towards fo rm a tio n o f a pronounced shou ld er on th e sample band at in j e c t io n s
o f o n ly 0 .0 2 m l. m ethane.

More oxygen flo w in g allow ed la r g e r samples to

be in j e c t e d w ith o u t undue t a i l i n g , but the s e n s i t i v i t y o f th e d e te c to r
a ls o began t o f a l l o f f .
S m all v a r ia t io n s in d e te c to r cu rren t and resp on se am plitude could be
made by o p era tin g th e T e sla c o i l primary from a v a r ia b le au totran sform er.
E . R e su lts and D isc u ssio n
1 . P h otom etric O b servation s
a . G eneral
From v i s u a l o b se r v a tio n , w ith a sm a ll spectroscope^ of th e glow d i s ­
charge in th e e x c it e r tu b e in th e reg io n o f th e tube observed by th e
p h o t o c e ll in F ig u re $ 9 i t was b e lie v e d th a t th e r e were s e v e r a l workable

106

p o s s i b i l i t i e s .for o p era tin g a photom etric d e te c to r •

In a d d itio n t o

changes in o v er”a l l i n t e n s i t y o f th e d isch a rg e when samples p assed through
th e e x c it e r tube,, c e r t a in r e g io n s o f th e spectrum were e s p e c i a ll y su b je c t
t o changeo

F ir s t ,, th e str o n g s p e c t r a l l i n e s o f th e c a r r ie r gas were

quenched, as had b een observed in th e work in P art I o f t h is i n v e s t ig a t io n .
S e c o n d ly , v a r io u s r e g io n s o f th e spectrum became e s p e c i a ll y in te n s e when
th e sample p a ssed through th e d isc h a r g e .

Various com binations o f p h o to c e ll

resp o n se and l i g h t f i l t e r s were t r ie d f o r v a rio u s c a r r ie r g a ses in attem pt­
in g t o f in d com binations o f components f o r s e l e c t i v e o b se r v a tio n o f s p e c ie s
in t h e d is c h a r g e .
The r e s u lt s ob tain ed w ith th e photom etric d e te c to r were la r g e ly
q u a l i t a t i v e in n a tu r e , b ecau se th e most prom ising a v a ila b le p h o t o c e ll,
th e GdS c e l l , (G L -2), developed a n o isy leak age cu rren t b e fo r e much q u a n ti­
t a t i v e work was done .

S in ce th e c e l l was always m aintained w e l l out o f

co n ta c t w ith th e d isc h a r g e tu b e , i t i s b e lie v e d th a t th e f a il u r e o f th e
c e l l was n o t induced by th e d is c h a r g e »
ho O v e r -a ll L igh t I n t e n s i t y ■>
As has been m entioned in th e in tr o d u c tio n to P art I I of t h i s work,
th e o v e r - a l l l i g h t i n t e n s i t y changes occu rrin g when organ ic vapors p ass
through a T e sla e x c ite d glow d isch a rg e w ith argon c a r r ie r g a s , are d is ­
t i n c t l y v i s i b l e due t o th e stro n g b lu e -g r e e n em issio n bands o f th e "Swan
system o f th e Cs m olecu le * In a d d itio n , i t has b een found th a t w ith
argon c a r r ie r gas flo w in g through th e d e t e c to r , sam ples o f organ ic vapors
are c l e a r l y v i s i b l e a t i n j e c t i o n volumes o f th e order o f 0 .0 1 m l.

10?

W ith a ir c a r r ie r gas* t h i s i n j e c t io n volume i s l e s s s t r i k i n g l y v isib le ®
The s e n s i t i v i t y o f v i s u a l in d ic a tio n w ith e it h e r a i r or argon c a r r ie r s ,
b u t e s p e c i a l l y w ith argon, seems adequate t o a llo w u se o f such a sim p le
d e te c to r t o m onitor th e e f f lu e n t stream from a p r e p a r a tiv e chrom atographic
column u sin g a s u it a b le s t r e a m - s p lit t in g arrangement t o b le e d o f f a sm a ll
p o r tio n o f t h e e f f l u e n t t o send through th e discharge®

Moreover, s in c e

a v i s u a l r esp o n se i s ob tain ed u sin g a ir c a r r ie r and sample s i z e s which
are sm a ll enough t o be handled by a sm a ll chrom atographic column, i t appears
t h a t t h i s sim p le d em on stration can be conducted u sin g a ir a t atm ospheric
p r e ssu r e as a c a r r ie r g a s »

I t has a ls o been determ ined th a t th e demon­

s t r a t i o n can be made w ith a ir a t p r e ssu r e s in th e d e te c to r which are
a t ta in a b le w ith a w ater a s p ir a to r in p la c e o f a vacuum pump® With argon
and h eliu m , as w i l l be d is c u s s e d in more d e t a i l b elow , th e d isch a rg e and
resp o n se t o s m a ll sam ples i s su sta in e d v i s i b l y to p ressu res above atmos­
p h e r ic , so th a t th e vacuum pump may be d isp en sed w it h .
The o v e r - a l l l i g h t i n t e n s it y did not appear t o o f f e r good p o s s i b i l i t i e s
f o r o th e r th an g ro ss q u a n tit a tiv e work, b ecau se th e v a r io u s p o r tio n s o f
th e spectrum w ent through maxima in in t e n s i t y a t d if f e r e n t s ta g e s o f th e
p ro g ress o f th e sample through th e d e t e c to r , r e s u lt in g in com plicated
resp o n se p a tte r n s of th e p h o to c e ll f o r a s in g l e band o f vapor®

This

o b se r v a tio n , to g e th e r w ith o b se rv a tio n s in P art I o f t h i s work, su ggested
two i n t e r e s t i n g a s p e c ts o f th e d isch a rg e t o in v e s t ig a t e s

(1 ) making th e

d e te c to r s p e c i f i c f o r c e r t a in su b stan ces by i s o l a t i n g s p e c t r a l r e g io n s ,
which f a l l on th e p h o t o c e ll, u sin g e it h e r f i l t e r s or a monochromator,
and ( 2 ) q u a l i t a t i v e a n a ly s is o f components e f f lu e n t from th e chrom atographic

108

column by s p e c tr o s c o p ic o b se r v a tio n o f th e changes o c cu rrin g i n th e d i s ­
charge as components p a ss a p o in t in th e d e t e c t o r *
Co Quenching o f C a rrier Gas
Experim ents w ith a r e d - s e n s it i v e p h o to c e ll (cadmium s e le n id e ) t o d e te c t
th e quenching o f c a r r ie r gas em issio n by sample vapors were performed*
Helium and argon c a r r ie r s were stu d ie d at atm ospheric p ressu re by h aving
th e pump c lo s e d o f f and v e n tin g th e c a r r ie r gas t o th e atmosphere through
stop cock SA in F ig u re 7 •

Helium has a v e r y stro n g y e llo w l i n e which i s

quenched by o rg a n ic vapors , w h ile argon has s e v e r a l red l in e s which are
quenchedj t h i s quenching i s d e te c ta b le f o r sm a ll sam ples w ith th e cadmium
s e le n id e p h o to c e ll*

The arrangement was n ot v ery good f o r hydrocarbons,

how ever, b e c a u se , alth ou gh stro n g quenching o f th e c a r r ie r l i n e s occu rred ,
hydrogen formed in th e d isch a rg e em itted s tr o n g ly in th e red*

With h elium ,

a y e l l o w - s e n s it i v e d e te c to r would have been v e r y s e n s i t i v e , ju dgin g from
th e spectrum*

N itro g en and oxygen were s tr o n g ly d if f e r e n t ia t e d in th e

d e t e c t o r , however*

The oxygen s tr o n g ly quenched th e c a r r ie r gas, w h ile

th e n itr o g e n was r a th e r in e f f e c t iv e *

T his was observed a ls o in F a rt I ,

where i t was found th a t th e a rc l i n e s of argon were quenched by oxygen
and n o t by n itro g e n *

Such a s it u a t io n could form th e b a s is f o r th e

a n a ly s is o f oxygen i n n itr o g e n or a ir m ix tu res 3 u sin g th e d e te c to r w ith ­
out a s e p a r a tin g column*
d* S e l e c t i v e O b servation o f E m ission by th e Sample
The predom inant change v i s i b l e in th e d e te c to r d isc h a r g e when organ ic
vapors p a ssed through was th e green em issio n band of th e C2 Swan system

109

a t 517 roju. o For b o th a ir and argon d isc h a r g e s , t h is p o r tio n o f th e
spectrum was o f low l i g h t i n t e n s i t y , as can be seen from th e low back­
ground cu rren t ( I 0 ) measured f o r a cadmium s u lf id e p h o t o c e ll w ith a green
f i l t e r , recorded in Table V I.

Argon em issio n can be seen t o be low er in

t h i s r e g io n than i s a i r 0 The resp o n se o f th e p h o to c e ll t o v a r io u s s m a ll
sample i n j e c t i o n s i s a ls o l i s t e d in th a t t a b le .

At a p r e ssu r e o f 3 mm.,

th e argon c a r r ie r produced a response of 135 microamp . t o 0 .0 1 m l. o f
m eth an e,w h ile th e a ir c a r r ie r produced a much lower resp on se f o r 0*05 m l.
m ethane.

Moreover^ th e argon c a r r ie r produced o n ly 0 .3~fliicroamp. resp on se

t o a 0 *05~mlo sample o f a i r „ These f a c t s in d ic a te s

( l ) th a t argon

c a r r ie r w ith a green—s e n s i t i v e p h o to c e ll forms a s e n s i t i v e d e t e c to r f o r
c a r b o n -co n ta in in g compounds, and (2 ) th a t i t may be p o s s ib le t o an alyze
o rg a n ic sample vapors mixed w ith a i r , even w ith o u t a chrom atographic
column, u sin g argon c a r r ie r g a s , because o f th e low s e n s i t i v i t y o f t h is
d e t e c to r t o a i r .

U sing argon c a r r ie r , th e s e n s i t i v i t y o f t h i s d e t e c to r ,

as measured by th e s ig n a l t o n o is e r a t io a t which a 0 .0 1 - m l. sample o f
methane gas can be d e t e c te d , i s about eq u al t o th e most s e n s i t iv e form o f
th e e l e c t r i c a l d e t e c to r em ploying argon c a r r ie r , which w i l l be d escrib ed
la te r .

These s e n s i t i v i t i e s are l i s t e d in Table VII t o be d isc u s se d l a t e r .

e . Q u a lita t iv e A n a ly sis o f Chromatographic Components
A ttem pts w ere made w ith th e sm a ll v i s u a l sp e ctro sco p e t o d is t in g u is h
betw een v a r io u s com p ounds p a ss in g through th e d e te c to r d is c h a r g e .

I t was

hoped th a t one might be a b le t o d is t in g u is h v i s u a l l y betw een hydrocarbons
and carb on yl compounds in th e d isc h a r g e , s in c e in F a rt I o f t h i s work i t

110

TABLE VI
RESPONSE OF PHOTOMETRIC DETECTOR TO VARIOUS SAMPLES,
CADMIUM SULFIDE PHOTOCELL, WRATTEN No. ?U
GREEN FILTER, 90 VOLTS

C a rrier
Gas
Ar

A ir

Sample
OoOl m l. CH4

IQ
(jia)
Ool

AI
{pa)

N oise
(P-*)

135

0.01

0o05 mlo a ir

0 .3

0 .2 5 mlo a ir

Q*h

QoQ£ m l. CH4
0 025 ®lL0 ch4

l'S

0 .2
2 .3

0 .0 5

I ll

was observed w ith th e sp ectrop h otom eter th a t carbon monoxide was a pre­
dom inant e m itte r in th e d eco m p osition o f o x y g en -co n ta in in g organ ic
compounds .

The e m issio n spectrum o f C2 and CO in an argon or a i r d i s ­

charge appear so s im ila r in th e v i s u a l sp e ctro sco p e th a t d i s t i n c t i o n o f
th e two k in d s o f compounds proved im p o ssib le v i s u a l l y .

They c o u ld , o f

c o u r se , be d is t in g u is h e d w ith a h ig h er d is p e r s io n s p e c tr o s c o p e , or
spectrophotom eter^ as was used in P art I .
C e r ta in s p e c ie s were amenable t o v is u a l d i f f e r e n t i a t i o n in th e d i s ­
ch arge, b u t in many in s ta n c e s th e s e d i s t i n c t io n s would b e t r i v i a l .

For

exam ple, e m iss io n b y th e fo llo w in g sim p le components could be seen in an
argon d isc h a r g e s

h eliu m , hydrogen, n itr o g e n , oxygen, and a ir«

Carbon

t e t r a c h lo r id e could be d is tin g u is h e d from ch loroform by v ir t u e o f th e
absence o f e m issio n from th e fragm ent CH w ith th e carbon t e t r a c h lo r id e .
T his method o f q u a l i t a t i v e a n a ly s is u sin g a h ig h er d is p e r s io n
sp e c tr o sc o p e or sp ectrop h otom eter seems capable o f alm ost u n lim ited
e x te n s io n in s c o p e , e s p e c i a l l y i f rap id scan ning tech n iq u es were a p p lie d .
With con tin u ou s m on itorin g o f th e d isch a rg e w ith a s p e c t r a l scan nin g
p h o to m u ltip lie r whose ou tpu t was d isp la y e d as a fu n c tio n o f w avelength
on an o s c illo s c o p e s c r e e n , th e observed breakdown p a tte r n o f th e sample
p a s s in g through th e d isc h a r g e could undoubtedly be used t o d is t in g u is h
betw een pure hydrocarbon and oxygenated organic compounds.

Other h e te r o ­

atoms should be o b serv a b le from fragm ents th e y form in th e d isch a rg e,
such as NH, SH, &2»

F u rther r a m ific a tio n s o f t h i s method w i l l be

summarized i n a l a t e r s e c t i o n .

112

f . S t a b i l i t y o f th e D ischarge
Perhaps th e most s t r ik in g o b se r v a tio n t o come out o f th e o b se r v a tio n
o f th e v i s i b l e d isc h a r g e in v a r io u s c a r r ie r g a ses i s th e s t a b i l i t y o f th e
argon and h eliu m d isc h a r g e s compared t o a ir or n itr o g e n under comparable
c o n d itio n s o W ith th e T e s la c o i l a v i s i b l e d isch a rg e could b e m aintained
e a s i l y in th e ra r e g a ses above atm ospheric p r e s s u r e , w h ile a i r and n itr o g e n
d isc h a r g e s became v e r y u n sta b le a t moderate p r e ssu r e s and were no lo n g er
v i s i b l e above about 3$Q mm* p r e s s u r e » T his i s a v e r y u s e f u l p ro p erty o f
th e r a r e g a se s which can a llo w u se o f a T esla d isc h a r g e d e t e c to r a t
atm osp h eric p r e ssu r e in m onitoring flo w system s w ith o u t a vacuum system .
The e x p la n a tio n f o r th e s t a b i l i t y o f th e ra re gas d isc h a r g e s i s p r e - _
sumed t o l i e in th e e x is t e n c e o f m eta sta b le rare gas atoms which have
r e l a t i v e l y lon g l i f e t i m e s in th e d isch a rg e sy stem .

These m e ta sta b le atoms

have s u f f i c i e n t en ergy t o ( 1 ) become io n iz e d b y e le c t r o n impact w ith r e la ­
t i v e l y low energy e le c t r o n s , and (2 ) t o io n iz e oth er m eta sta b le ra re gas
atoms i n a s u i t a b l e c o l l i s i o n p r o c e s s .

S in c e th e T e sla c o i l output i s a

ra d io fr e q u e n c y v o l t a g e , p u ls a t in g a t 120 c y c le s p er seco n d , i t has t o
i n i t i a t e th e d isc h a r g e many tim e s a secon d .

I f a good su p p ly o f m eta sta b le

atoms i s p r e se n t when th e T e s la output c u ts o f f , th e s e atoms may se r v e t o
keep io n iz a t io n p r o c e s s e s g o in g i n th e system because o f item (2 ) above,
and a l s o become io n iz e d more r e a d ily when th e T esla output comes on a g a in
b eca u se o f item ( 1 ) .
We s h a l l s e e from th e s tu d ie s o f the e l e c t r i c a l d e t e c to r b elo w , th a t
o f th e r a r e g a ses argon and h eliu m , argon seems to produce by f a r th e more
s t a b le d is c h a r g e , perhaps due t o th e low er iq eta sta b le l e v e l and io n iz a t io n
p o t e n t ia ls o f argon.

113

go Summary
I n summary i t may be s a id th a t a p h otom etric d e t e c to r u sin g a T e sla
e x c it e d glow d isc h a r g e shows c o n sid era b le prom ise as a s e n s i t i v e d e t e c to r
f o r gas chromatography*

The s e n s i t i v i t y o f th e green—s e n s i t iv e photo­

m e tr ic d e t e c to r f o r hydrocarbons u sin g argon c a r r ie r gas appears t o be as
g r ea t as th a t o f th e e l e c t r i c a l d e te c to r t o be d escrib e d below*

The low er

l i m i t o f hydrocarbon d e t e c t a b i l i t y as estim a ted in a l a t e r s e c t io n ,
appears t o b e s l i g h t l y g r e a te r than t h a t o f a k atharom eter, b u t n o t so
g r e a t as th e io n iz a t io n d e te c to r s d escrib e d in th e in tr o d u c to r y p o r tio n s
o f P a r t II*
Use o f a narrower bandpass f i l t e r (perhaps an in te r fe r e n c e f i l t e r )
or a monochromator would reduce th e background l i g h t i n t e n s i t y and th e
accompanying n o is e l e v e l o f th e ph otom etric d e t e c t 01^ w h ile a t th e same
tim e making th e d e t e c to r s p e c i f i c f o r a p a r t ic u la r s p e c ie s in th e d isch a rg e;
t h i s cou ld r e s u l t in an a p p r e c ia b le in c r e a s e in s e n s i t i v i t y o f t h i s d e te c to r *
The a p p l i c a b i l i t y o f t h i s d e te c to r w i l l be d isc u sse d fu r th e r a f t e r
th e o b se r v a tio n s u s in g th e e l c t r i c a l d e te c to r have been reported*
A com parison o f th e two d e t e c to r s w i l l be p resen ted a lso *
2 * The E l e c t r i c a l D e te c to r —R e s u lts and D is c u s s io n
a* S e l e c t i o n o f System s f o r Study and D isch arge
O p eratin g C o n d itio n s
(1 )

C a rrier Gases*

The resp o n se o f th e e l e c t r i c a l d e te c to r was

s tu d ie d m ain ly w ith a i r and w ith argon c a r r ie r g a s e s , or argon w ith oxygen
sca v en g er fe d in t o th e d e te c to r *
A r(^02) c a r r ie r *

The l a t t e r case i s r e fe r r e d t o as

A ir was co n sid ered t o be o f p a r t ic u la r I n t e r e s t , b ecau se

lilt

i t s u se would make a c o m p le tely in ex p en siv e d e t e c to r f o r le c t u r e demon­
s t r a t i o n p u rp o ses, b e s id e s th e p o s s ib le a p p lic a tio n t o d e t e c t io n o f
atm osp h eric p o llu t a n t s and t o d e t e c t io n o f su b sta n ces sampled in th e vap or
s t a t e d i r e c t l y in a i r *
For p r e p a r a tiv e w ork, o f c o u rse, an in e r t gas i s o f te n d e s ir a b le .
Argon seemed e s p e c i a l l y a t t r a c t i v e as a c a r r ie r gas, b ecau se e a r ly e x p e r i­
ments showed th e argon d isc h a r g e t o be e s p e c ia lly s t a b le ( f r e e from n o i s e ) .
T his i s i l l u s t r a t e d by th e n o is e l e v e l s observed w ith v a r io u s c a r r ie r g a se s
l i s t e d i n T ab le V II o Argon performed much b e t t e r than helium and i s th e
cheaper o f t h e s e tw o, so i t was s e le c t e d f o r a more d e t a ile d stu d y .
The s e n s i t i v i t y o f th e d e t e c to r u sin g n itr o g e n as a c a r r ie r gas
seemed comparable t o th a t w ith a i r , but th e d e te c to r had a ten d en cy to
produce str o n g t a i l i n g , much as happened a t f i r s t w ith argon b e fo r e th e
oxygen sca v en g er was in tr o d u c e d » N itrogen probably could be used f o r
p r e p a r a tiv e w ork, i f d e s ir e d , b y in tr o d u c in g th e oxygen scaven ger a f t e r
th e chrom atographic column and b e fo r e th e e x c i t e r , as was done w ith argon.
(2 ) Apparent E l e c t r i c a l C h a r a c te r is tic s o f th e D e te c to r D isch a rg e.
The d i r e c t cu rren t e le c t r o n flo w from th e in n er e le c tr o d e o f th e t e e tu b e ,
through th e m eter, s e r i e s r e s i s t o r , b a t te r y and back to th e o u ter p o r tio n
o f th e t e e tu b e (F ig u re 6 A \ i s p r o p o r tio n a l t o th e v o lta g e a p p lied by
th e b a t t e r y a t m oderate cu rren t f lo w .
in F igu re 8 .

This i s i l l u s t r a t e d f o r a ir c a r r ie r

I f one assumes th e t e e t o c o n s is t o f a so u rce o f p o t e n t ia l ,

E, and an in t e r n a l s e r i e s r e s is t a n c e , R, th en from th e slo p e and in t e r ­
cep t o f t h i s l i n e one can c a lc u la t e th a t w ith th e e x te r n a l s e r i e s
r e s is t a n c e o f one megohm in th e c i r c u i t , th e v a lu e o f E i s about 5 v o l t s

H5

TABLE 711

ESTIMATED SIGNAL TO NOISE RATIOS FOR AIR, ARGON AND
HELIUM CARRIERS— RESPONSE TO O .O l ML.
METHANE INJECTION

C a rrier
Gas

E le c tr o d e

P(nun)
Approx.

Time
C onstant
_ ( s e c .)

N oise
()ia)

lo
(p O

£1
(p O

S ig n a l
N oise

E l e c t r i c a l D e te c to r
A ir

l / l 6 in .

k

2

0 .5

5 -1 0

N2

1 /1 6

k

2

0 .5

5 - io

Ar”

1 /1 6

h

0 .2

0 .2

12

A ir

1 /8

3

2

0 .1 7

Ar*

1 /8

3

0 .2

Ar(*Oa) * l / 8

3

He

U .0

8

7h

ho

1U.7
U.0

0 .1 0

CLU

U2

0 .2

0 .1 0

m

130

1300

3
20

2

3

5

1

2

5
2

7

6

2

0 .2 5

19

15

1 /8

7h
160

3
60

2

0 .1

1 /8

Uoo

2

0 .2

1U
~ 0

1 /8
1 /8
1 /8

2h
U20

7a

71

1.9

9

P h o to m etric D e te c to r
Cadmium S u lf id e P h o t o c e ll, 90 V o lts , Green F i l t e r
Ar

1 /8

3

0 .2

~ 0 .0 1

135

0 .1

~ 1350

A ir**

1 /8

3

0 .2

—- 0 .0 5

0 .2

1 .5

U

^ 0 .1 - Megohm r e s i s t a n c e , i . e . , most s e n s i t i v e s c a le .
**0o 05 m l. methane in j e c t e d .

116

0

10

20

30

40

APPLIED

FIGURE 8.
P = 3 .6 M M ,

DETECTOR
ONE

CURRENT

MEGOHM

50

60

70

80

90

VOLTAGE

VS, APPLIED

RESISTOR,

VOLTAGE;

£ IN.

AIR

ELECTRODE.

CARRIER,

117

and R i s ap p ro x im a tely 0*5 megohmo

I f th e one-megohm e x te r n a l r e s is t a n c e

i s shunted b y a 0 *X-raegohm r e s i s t o r however* th e cu rren t in c r e a s e s by
ap p ro x im a tely a f a c t o r o f 7 w ith a i r c a r r ie r , as though th e in t e r n a l
r e s is t a n c e o f th e t e e w ere alm ost n e g l i g i b l e , compared t o 0 , 1 megohm*
The e f f e c t o f t h i s s c a le - m u lt ip ly in g r e s is t a n c e i s shown i n T able V III
f o r argon and helium *

For argon th e 0 * 1 -megohm r e s i s t o r m u lt ip lie s th e

cu rren t b y ap p roxim ately 1 0 , b u t t h i s f a l l s o f f a t h ig h er p r e s s u r e , where
th e c o n d u c t iv it y o f th e gas could be presumed t o be lower*

The v o lta g e —

cu rren t r e la t io n s h ip w ith th e s e c a r r ie r g a ses i s a ls o lin e a r a t low
v a lu e s o f cu r re n t flow *
The s e n s i t i v i t y o f th e d e t e c to r t o hydrocarbons f a l l s o f f s lo w ly as
th e a p p lied v o lta g e in c r e a s e s f o r a l l th r e e c a r r ie r g a s e s , so g e n e r a lly no ex­
t e r n a l v o lta g e was a p p lie d .

The e f f e c t on s e n s i t i v i t y was n ot n o tic e a b le

f o r v o lt a g e s l e s s th an about th r e e v o l t s , however, so s l i g h t “zero a d ju s tin g 11
v o lt a g e s could be a p p lied w ith o u t changing th e s e n s i t i v i t y o f th e d e te c to r
a p p recia b ly *
( 3 ) E f f e c t o f P r e ssu r e on D e te c to r P r o p e r tie s*

The d e t e c to r cu rren t

measured f o r v a r io u s c a r r ie r g a s e s as a fu n c tio n o f p ressu re i s i l l u s ­
t r a te d i n F ig u re 9 *

The cu rren t w ith th e g a ses n itr o g e n and a ir shows a

s im ila r p r e s su r e dependence, th e cu rren t p a ssin g through a maximum a t a
p r e ssu r e n ear tw en ty m illim e te r s o f mercury*

The cu rren t w ith argon

c a r r ie r i s v e r y lo w , b u t a ls o shows a p ressu re dependence w ith a maximum
n ear t h i r t y m illim e te r s p ressu re*

The maximum cu rren t in th e s e th r e e

c a se s i s a p p roxim ately f i f t y p e rcen t h igh er th an th e cu rren t observed a t
th e lo w e s t p r e s su r e s s tu d ie d (2-1* ram)*

This low p ressu re r e g io n r e p r e s e n ts

118

TABLE V III

EFFECT OF SCALE MULTIPLIER RESISTANCE ON CURRENT IN THE ELECTRICAL
DETECTOR FOR ARGON AND HELIUM AT VARIOUS PRESSURES,
1 /1 6 IN* ELECTRODE, RUN 33*

Argon
p

j

Helium

(mm.)

)
1 meg.

t (pa )
0 . 1 meg.
0 .1 meg. I ,
go

p

U.U

1 .2 0

13.0

10.8

h-3

3.6

31-5

7 *3

3U

1.88

18.8

10.0

9

U.o

3 3.5

8.U

U2

lo ? 2

17 *3

10.2

1U

U .8

Ul.G

8.5

5U

l.iiO

lUoO

10.0

17

5.5

U3.5

8.7

6U

1-15

10.5

9-1

75

.0.90

6.5

7-2

91

0 .2 5

0.65

2.6

(mm.)

j Qia)
1 meg.

j (/*a )
-^q t me~
0 .1 meg. p - 1------1 me,g.

119

20.0

-AIR

5.0

—

Ar

00
200

100

j

300

400

P ( M M . HG)

FIGURE 9.
AND

HE

DETECTOR
CARRIER

CURRENT

GASES;

ONE

VS

PRESSURE

MEGOHM

FOR

N2, AIR,

RESISTOR, ^ IN.

AR,
ELECTRODE.

120

th e normal o p e r a tin g r e g io n used in t h is work*

Helium was found t o have

a cu rren t maximum a t about n in e ty m illim e te r s p res sure , t h is maximum be­
in g s e v e r a l tim es th e cu rren t c h a r a c t e r is t ic o f th e low p ressu re end o f
th e curve 0
The resp o n se o f th e d e te c to r to sample g a s e s , w i l l be d efin ed h ere
as th e c u r r e n t,

A I , which i s th e d iff e r e n c e betw een th e output cu rren t

o f th e d e t e c t o r when i t i s resp on din g t o a sample vapor and th e b a s e lin e
cu rren t I Q w hich i s a c h a r a c t e r is t ic of th e c a r r ie r gas •

The resp on se

o f th e d e t e c t o r t o v a r io u s a ir s o lu t io n s o f sample gases as a fu n c tio n o f
p r e ssu r e in a ir c a r r ie r i s i l l u s t r a t e d in F igu res 10 and 1 1 .

I t was found

t h a t f o r a U»2 volume p ercen t s o lu t io n o f methane in a ir (F igu re 10) and
fo r a

volume p e rc en t s o lu t io n o f hydrogen in a ir (F igu re 11) th e

resp o n se o f th e d e t e c to r t o th e s e g a ses showed maxima in th e v i c i n i t y o f
tw en ty m illim e te r s o f p ressu re, or v e r y c lo s e to th e p r e ssu re g iv in g th e
maximum in d e t e c to r cu rren t f o r a i r i t s e l f .

For a k9 *3 volum e p ercen t

s o lu t io n o f h elium i n a i r , however, th e maximum resp on se was observed
near f i f t y m illim e te r s p r e s s u r e .

The r e la t io n s h ip o f resp on se cu rren t

f o r a h e liu m -a ir s o lu t io n seems to be an a d d itiv e one, th e maximum in
resp o n se f a l l i n g betw een th a t f o r a ir i t s e l f and th a t f o r helium i t s e l f .
I t has b een a s c e r ta in e d q u a l i t a t i v e l y th a t th e respon se o f th e
d e t e c to r t o i n j e c t i o n o f 0 .0 1 m l. methane u sin g argon c a r r ie r gas a ls o
goes through a maximum near t h ir t y m illim e te r s of p r e s s u r e .

With helium

c a r r i e r , a maximum resp o n se was observed f o r methane t o occur in th e
v i c i n i t y o f one hundred m illim e te r s p ressu re (T able V I I ) .

121

O I , AIR
O ' A I , 4.2 VOLUME PERCENT
METHANE
cp A I , 49.3 VOLUME PERCENT

HELIUM

<t)
A

UJ

CK
CH
3)
O

0.0

—

-5 .0 —

10

20

30

40

50

P (M M

FIGURE

10 .

RESPONSE
ELECTRODE,

METHANE AND
VS.

PRESSURE.

2 0 M L.

60

70

INJECTIONS.

90

100

AIR

CARRIER;

HG)

HELIUM SOLUTIONS

ONE

80

MEGOHM

SERIES

IN AIR,

RESISTOR,

IN.

122

9

A I , 4 9 .3 VOLUME
PERCENT HYDROGEN

30.0

o

10.0

60

10

P (M M

HG)

FIGURE 11.
RESPONSE
TO 4 9 .3
VOLUME PERCENT HYDROGEN
SOLUTION IN AIR.
AIR CARRIER.
ONE MEGOHM RESISTOR^
4? IN. ELECTRODE,
2 0 M L. IN JEC TIO N S.

123

W ith a i r and argon c a r r ie r s th e r e seemed t o be l i t t l e gained by
o p e r a tin g th e d e t e c to r near th e s e maxima in response* b ecau se th e n o is e
l e v e l a ls o in c r e a se d a lon g w ith th e r e sp o n se .

In th e c a se s o f argon and

helium * w ith maxima in resp o n se a t r e l a t i v e l y high p ressu res* th e flo w
r a te w ith th e d e t e c to r a t a h ig h p ressu re was much to o slow t o g iv e rap id
p a ssa g e o f components through th e d e t e c t o r .

The method o f p ressu re c o n tr o l

in th e d e t e c to r was p a r t i a l l y t o blame f o r t h i s s it u a t io n .

The p r e ssu r e

was in c r e a se d b y t h r o t t l i n g th e pump* th ereb y cau sin g a d ecrea se in flo w
r a te t o o c c u r .

I t i s p o s s ib le th a t s a t i s f a c t o i y fle w r a t e could be

combined w ith optimum o p er a tin g p ressu re by in c r e a s in g th e flo w a t th e
f lo w - l i m it i n g c a p il la r y p la ced a t C in F igu re 7 •

This method* however,

would ten d t o u se u n d e sir a b ly h igh q u a n tit ie s o f argon and h eliu m .

S in c e

an in c r e a s e in s ig n a l - t o - n o i s e r a t io o f no more than th r e e was fo r e s e e n
f o r such o p e r a tio n o f th e d e te c to r * i t was operated w ith th e f u l l pumping
r a t e o f th e vacuum pump a p p lied t o th e d e te c to r * w ith th e flo w through
th e l i m i t e r a t C (F ig u r e 7 ) r e s t r i c t e d t o keep a p r essu re o f 2—Ij. mm.
in s id e th e d e t e c t o r .
b . Response o f D e te c to r U sing A ir C arrier
(1 )

L ig h t G a ses.

The resp o n se o f th e d e te c to r as a fu n c tio n o f th e

c o n c e n tr a tio n o f v a r io u s sample g a ses in a ir u sin g a ir as a c a r r ie r gas
i s shown i n F ig u re 12 and Table IX .

F igu re 12 shows th a t n itrogen * argon

and heliu m d e c r e a se th e d e t e c to r cu rren t s l i g h t l y w h ile hydrogen and
methane (and hydrocarbons in g en era l in Table IX) cau se a stro n g in c r e a s e
i n d e t e c t o r c u r r e n t.

The cu rves show lin e a r r e s p o n se -v e r su s -c o n c e n tr a tio n

TO

o

o
CO

C\J

o

o

Q

O

C Q 'ri)

IV
SOLUTIONS. IN AIR-,

O

o

cc

o ^
Vo

LU

LU

VARIOUS

O
oo

OF

o

INJECTIONS

cc

20ML

AIR

O
O

RESPONSE

CARRIER.

O
O

FIGURE 12.

22k

o

O

125

TABLE H
RESPONSE IN AIR CARRIER TO 20 ML. INJECTIONS OF 1 .1 VOLUME PERCENT
SOLUTIONS IN AIR FOR VARIOUS SAMPLE GASES
P r e ssu r e » 3 *7 nun* > One Megohm R e s is t o r , l / l 6 in * E lec tr o d e

AI

fyia)

Helium*

- 0 .0 6

Argon

- 0 .0 1

Hydrogen

♦ 2 .8

A cety len e

3 *6

Methane

U-7

E th ylen e

5*5

Ethane

7*3
9 .2

Cyclopropane
P rop ylen e

11. u

Propane

11 *6

1-B utene

13*0

^ E stim ated b y e x tr a p o la tio n o f curve in F ig u re 12 t o th e o r ig in .

126

f o r methane up t o one volume p e r c e n t, f o r hydrogen up t o about two volume
p e r c e n t, and f o r h eliu m up t o about f o r t y volume p ercen t in a i r .

The

s e n s i t i v i t y o f th e d e t e c to r t o th e s e su b sta n ces i s adequate t o a llo w
q u a n t it a t iv e d e te r m in a tio n o f th e s e sample g a ses in t h e ir ran ges w ith in
a few p ercen t*

The resp o n se o f th e d e te c to r t o n itr o g e n u sin g a ir c a r r ie r

i s to o low t o be o f much v a lu e in m easuring n itr o g e n enrichm ent in a i r .
The r e sp o n se curve o b ta in ed f o r argon s o lu t io n s i n a i r i s d i f f e r e n t in
form from t h e r e s t o f th e curves in F igu re 1 2 .

The resp on se to argon

appears l i n e a r w ith r e s p e c t t o c o n cen tra tio n o f argon f o r com p osition s
n ea r pure a rg o n , w h ile th e resp on se curve seems t o approach th e concen­
t r a t i o n a x is a s y m p to tic a lly f o r s o lu t io n s approaching pure a i r .
(2 } R e p r o d u c ib ility .

R e p r o d u c ib ility t o w it h in te n p e r c e n t in r e s p o n se -

v e r s u s -c o n c e n tr a tio n cu rves l i k e th o se in F ig u r e s 11 and 12 could be
a ch iev ed q u it e r e a d ily even a f t e r d ism a n tlin g and rea ssem b lin g th e d e t e c t o r .
Although th e d e t e c to r was s u b je c t to v a r ia t io n s in s e n s i t i v i t y over lo n g
p e r io d s o f o p e r a tio n , s h o r t term o p era tio n (8 h ou rs) e x h ib ite d s t a b i l i t y
which would a llo w a n a ly s is to w ith in f i v e p ercen t in m eth an e-air s o lu t i o n s ,
f o r exam ple.

F lu c tu a tio n s in s e n s i t i v i t y were probably due in some p a rt

t o v a r ia t io n s in output from th e T e sla c o i l , alth ou gh t h i s was never
d e f i n i t e l y e s t a b lis h e d .

Probably th e g r e a t e s t source o f i n s t a b i l i t y was

d e p o s it io n o f p olym eric hydrocarbon m a te r ia l on th e e le c t r o d e s .

This was

n o t so apparent in a i r as i t was in th e ca se o f argon c a r r ie r , because
th e oxygen i s q u ite e f f e c t i v e in p rev en tin g such d e p o s it io n .
These r e s p o n se -v s .-c o n c e n tr a tio n s tu d ie s were made u sin g la r g e (20 m l.)
in j e c t i o n s o f th e s o lu t io n s o f s ta te d co m p o sitio n .

T his method was used

12?

so t h a t th e a c t u a l c o n c e n tr a tio n o f th e sample in th e d e te c to r would be
known« For a n a l y t i c a l work, however, sm a lle r sam ples could be used in
m ost in s t a n c e s .

T his would g r e a t ly d im in ish any change in p r o p e r tie s o f

th e e le c t r o d e due t o hydrocarbon d e p o s it io n .
(3 ) H igher H ydrocarbons.

Table IX shows th e resp on se o f th e d e t e c t o r

w ith a i r c a r r ie r t o hydrocarbons o f in c r e a s in g carbon c o n te n t.
f o r hydrogen, argon and helium are shown f o r com parison.

Responses

I t can be seen

th a t th e resp o n se to a hydrocarbon in c r e a s e s as th e number o f atoms in
th e m o lecu le in c r e a s e s .

The uflam e io n iz a t io n d e t e c t or11 o f McWilliam and

Dewar (6 1 ), th e !lb e ta -r a y io n iz a t io n d e te c to r 11 o f Lovelock ( 6 2 ) , and th e
r a d io fr e q u e n c y glow d isc h a r g e d e te c to r o f Karmen and Bowman (6U) are
rep o rted a ls o t o have s e n s i t i v i t i e s p r o p o r tio n a l t o th e number o f carbon
atoms or th e mass o f th e hydrocarbon.

In th e p r e se n t ca se, excep t f o r

a c e ty le n e , which produces l e s s resp on se than m ethane, th e order i s a ls o
th a t o f carbon number.
I n j e c t io n s o f 0 .0 1 - m l. sam ples o f th e hydrocarbon g ases in Table IX
gave r esp o n ses which were in th e same r e l a t i v e o rd er, as did th e in j e c t io n s
o f 20 m l. o f 1 .1 volume p e r c e n t s o lu t io n s in d ic a te d in th e t a b l e .
R esponses to 0 .0 1 - m l. i n j e c t i o n s o f a c e to n e , b en zen e, cy clo h ex a n e, n -hexan e,
and petroleum e th e r were comparable t o th a t o f b u te n e .
(k) Water Vapor.
m o istu re in a i r .

The d e te c to r was found t o respond m easurably t o

I n j e c t io n o f 20 m l. o f la b o r a to r y a ir from a room w ith

th e r e l a t i v e h u m id ity a p p roxim ately n in e ty p ercen t produced a resp on se o f
microamperes u sin g th e l / l 6 - i n . e le c tr o d e and one—megohm cu rren t
lim ite r .

D ilu t io n o f a s im ila r sample w ith an e q u a l volume o f dry a ir

128

produced a. r esp o n se o f 2*It microamperes*

The d e t e c to r can p rob ab ly be

used t o measure m oistu re co n ten t o f a ir q u a n t it a t iv e ly , and appears t o
have an a p p roxim ately l i n e a r resp on se curve over an a p p r e c ia b le range o f
w a ter-v a p o r c o n c e n tr a tio n in a i r .
Co R esponse o f th e D e te c to r U sing Argon C a rrier
(1 ) Oxygen S caven ger.

As has a lrea d y been m entioned, th e r e was a

stro n g ten d en cy f o r d e p o s it io n o f hydrocarbon polymer on th e e x c it e r w ire
and e le c t r o d e s when o rg a n ic samples were passed through th e T e sla d isc h a r g e
d e t e c to r u sin g argon c a r r ie r g a s .

In order t o u se wmacroM sam pling

te c h n iq u e s w hich were r e a d ily a v a ila b le , oxygen was used as a scavenger
f o r th e f r e e r a d ic a ls formed in th e argon-hydrocarbon d isch a rg e t o m inim ize
th e d e p o s it io n o f p olym eric s p e c ie s on the e le c t r o d e s .

The e f f e c t o f

oxygen was v i s i b l y a p p a ren t, as th e oxygen v i s i b l y quenched th e green
e m issio n in th e d isch a rg e due t o th e r a d ic a l C2, which i s p robably th e
main in te r m e d ia te in th e polymer d e p o s it io n .

Depending on th e amount o f

oxygen fe d in t o th e e x c i t e r and d e t e c t o r , a r b it r a r ily la r g e samples
could b e used w ith o u t undue t a i l i n g o f th e b a n d s.

For th e resp on se curves

i l l u s t r a t e d or ta b u la te d in t h i s s e c t io n , th e oxygen flo w was s u f f i c i e n t
t o a llo w p a ssa g e o f a 0 . 2 - m l. methane sample w ith o u t a t a i l i n g sh ou ld er
a f t e r th e p ea k .

This s t i l l req u ired o n ly a v e r y sm a ll amount o f oxygen,

which i s a h ig h ly e f f e c t i v e scavenger o f f r e e r a d ic a ls .
(2 ) M ethane.

F ig u re 13 d e p ic ts the resp on se o f th e d e te c to r to

la r g e in j e c t io n s o f raethane-argon s o lu t io n s .

The curve i s sig m o id a l in

sh a p e, f l a t t e n i n g out in th e r e g io n o f two volume p ercen t methane.

12?

150

140
130

20

100

!

90:
<9 8 0

<

60
50

40
3 0-

0.2

0.6

0 .4

VOL

FI CURE

13.

SOLUTIONS

RESPONSE
IN

TO

0.8

PERCENT

1.2

1.0

1.4

METHANE

5 0 M L. INJECTIONS

OF M ETHANE

ARGON.
A R (K )J CARRIER,
P = 3 .0 M M ,
0.1 M E G O H M RESISTOR.

130

There i s a li n e a r p o r tio n e v id e n t in th e resp on se curve betw een onete n th and fo u r -t e n th s volume p ercen t m ethane.

F igu re llj. shows th e r e ­

sp on se curve f o r in j e c t io n s o f methane g a s, u sin g a stream s p l i t ahead
of th e d e te c to r .

The s p l i t t i n g r a t io was ap proxim ately 12 t o 1 .

This

curve was tak en w ith th e one-megohm s e r i e s r e s i s t o r lim it in g th e cu r r e n t,
so th e cu rren t v a lu e s should be m u ltip lie d by about 10 t o be compared t o
th o se in th e p re v io u s f ig u r e .
in shape and s i z e .

I f t h is i s done, th e cu rves are v e r y s im ila r

This curve su g g e sts t h a t th e resp on se i s lin e a r in

th e r e g io n below about 0 .2 m l. methane in j e c t e d .

This corresponds t o

methane c o n c e n tr a tio n o f about 0 .1 volume p ercen t or about J4.OO ppm.
The n o n - lin e a r it y o f t h i s resp on se curve i s an u n d e sir a b le p ro p e r ty , bu t
i t appears th a t d e t e c t io n o f hydrocarbons up t o 1 .5 volume p ercen t in th e
vapor can be accom plished w ith o u t s a tu r a tio n o f th e d e t e c t o r .

An im portant

f e a tu r e o f th e d e t e c to r i s , how ever, th a t i t does respond to m olecu les
w ith i o n iz a t io n p o t e n t ia ls above th e m eta sta b le l e v e l o f th e c a r r ie r g a s.
In t h i s r e s p e c t th e d e te c to r i s alm ost unique among io n iz a t io n d e t e c t o r s .
(3 )

H igher H ydrocarbons.

Table X shows th e resp on se o f th e d e te c to r

t o 0 .6 volume p er ce n t s o lu t io n s o f hydrocarbons o f in c r e a s in g m olecular
w e ig h t .

The order o f resp o n se i s a g a in one o f in c r e a s in g m olecu lar w eig h t

o f th e compound, e x cep t th a t butene g iv e s a somewhat smal.Il.er respon se than
does propane.

I t may be th a t th e resp on se curve f o r a g iv en hydrocarbon

f l a t t e n s out a t a c o n c e n tr a tio n which produces about 150 microamperes
resp o n se w ith th e Q.l-megohm r e s i s t o r , and th en comes back down s l i g h t l y
a t h ig h e r c o n c e n t r a tio n s .

This could be due to so much hydrocarbon vapor

in th e argon d isc h a r g e th a t, a f t e r p a ssin g through th e e x c it e r tube, th e r e

AI

( m a)

131

5 —

ML. METHANE

FIGURE 14.
RESPONSE TO M ETH AN E
1 2 :1
STREAM SPLITTING RATIO. ONE
P=2 M M .

IN AR(-t-02) CARRIER;
MEGOHM RESISTOR,

132

TABLE X
RELATIVE RESPONSE TO 50 ML* INJECTIONS OF 0 .6 VOLUME PERCENT
SOLUTIONS OF HYDROCARBONS IN ARGQNj . Ar(*G2) . CARRIER
Qol Megohm R e s is t o r , I 0 ■ 13 »5

P « 3' mm., Ran 39‘b,

S o lu t io n

A I (jia)

Methane

78

E th y len e

89

E th y len e oxid e

90

Ethane

125

1-B utene

131

Propane

1L5

133

i s s t i l l much hydrocarbon which has n ot b een decomposed or io n iz e d .

This

u n io n iz e d hydrocarbon th en i s a m oderately e f f e c t i v e quenching agen t f o r
ft

th e d isc h a r g e and r e s u l t s in low er c o n d u c tiv ity o f th e d isch a rg e than was
c h a r a c t e r i s t i c o f s l i g h t l y low er c o n cen tra tio n s o f hydrocarbon.
r e s u l t , th e b u tene produces a low er resp on se than th e propane.

As a
This

h y p o th e s is could be checked r e a d ily by running t h is s e r i e s o f vapors a t
low er c o n c e n t r a tio n s .
(U) O rganic L iq u id s.

Responses o f th e d e te c to r t o argon -organ ic

vapor s o lu t io n s o f v a r io u s liq u id s are l i s t e d in Table X I.

The d a ta f o r

d il u t i o n s o f b e n z e n e-sa tu ra ted argon show an ap proxim ately lin e a r r e la tio n ^
s h ip over th e r e g io n 0 - 0 .2 6 volume p ercen t b en zen e.

The curve appears

sig m o id a l a g a in , goes through a maximum and ap p a ren tly f l a t t e n s out a t
h ig h e r c o n c e n tr a tio n s .
( 5 ) A ir .

The resp o n se o f th e d e te c to r t o a ir -a r g o n s o lu t io n s i s

shown in F ig u re 1 5 .

This resp on se appears t o be a sim p ler one than th e

hydrocarbon c u r v e s .

The curve r i s e s s t e e p ly from th e o r ig in , and th en

g r a d u a lly d e c r e a s e s in s lo p e as th e a i r co n c e n tr a tio n in c r e a s e s .

I t shows

th e same q u a l i t a t i v e c h a r a c t e r is t ic s as th a t obtained e a r l i e r (F ig u re 12)
f o r th e in v e r se sy ste m .

The r a te o f change o f resp on se w ith r e s p e c t t o

c o n c e n tr a tio n i s th e g r e a t e s t f o r co n cen tra tio n s n ear pure argon.

The

l a t e r curve was run a t ap p roxim ately te n tim es th e range o f resp o n se o f
th e e a r l i e r curve (u sin g th e 0.1-megohm s e r ie s r e s i s t o r a t th e l a t e r t im e ) .
(6 ) Sample Chromatograms.

Sample chromatograms were made u sin g th e

e l e c t r i c a l d e te c to r w ith argon c a r r ie r and oxygen scaven ger and a q u a r te r —
in ch d iam eter, s i x - f o o t packed column.

F igure 16A i s th e t r a c e ob tain ed

13 U

TABLE XI
RESPONSE TO 50 ML o INJECTIONS OF ORGANIC VAPOR SOLUTIONS
IN ARGON5 Ar(+Q2) CARRIER
0 . 1 Megohm R e sisto r * I 0 * 13 .5 ^ia* P « 2 .5 mm., Run UOa.

Organic
S u b stan ce

Benzene

Liquid
Temperature

f .p .

D ilu te d
w ith Ar t o „
V o l. P ercen t

Volume
P ercen t
Hydrocarbon

A I (jia)

1 .3

0 .0 6 0

11

Benzene

2 ob

0 .1 1

20

Benzene

5 .7

0 .2 6

61

Benzene

1 1 .2

0 .5 2

67

C yclohexane

f .p .

1 .3

0 .0 6 5

25

A cetone

0°C.

1 .3

H
H
0

19

Methane

1 .3

Methane

0 .1 0

130
7

TO

^

O
LO

CXI

o

O
°cd
^
Q_

o
o

0.1 MEGOHM

SOLUTIONS.
RESISTOR..

OF AIR-ARGON

LU

INJECTONS

9=
9
<
\C> •

P=2.7 M M ,;

50M L.

o

CARRIER.

RESPONSE

l\

15.

O
00

FIGURE

A R (+ 0 2)

1

35

o

136

f o r 0*25 m l- o f n a tu r a l g a s .
d u rin g th e major component.

The d e te c to r resp o n se was in t o s a tu r a tio n
The minor components show q u a l it a t i v e

correspondence betw een peak h e ig h t and th e a n a ly s is , b u t f o r accu rate
a n a l y t i c a l work c a lib r a t io n would be n e c essa ry f o r each component.
A h e a v ie r , broad component shows up , a t h ig h er s e n s i t i v i t y , about t e n
m inutes a f t e r t h e i n j e c t i o n p o in t .
rep o rted p r e s e n t a t

This i s p rob ab ly iso p en ta n e which i s

in th e g a s .

The u se o f th e chrom atographic column b e fo r e th e d e te c to r r e s u lte d
i n some l o s s in th e peak s ig n a l - t o - n o is e r a t io compared to th e v a lu e s in
T ab le VII*

T hese v a lu e s were th o se observed f o r d i r e c t i n j e c t io n o f a

methane sample w ith a f lo w - lim it in g c a p illa r y in p la c e o f th e column.
There was a s l i g h t amount o f spread in g o f th e bands on th e column, b u t t h i s
was n o t th e major sou rce o f s ig n a l- t o - n o is e l o s s .

I t was observed th a t

th e background cu rren t and n o is e r e g is te r e d by th e d e te c to r depended on
t h e c o n d itio n o f th e chrom atographic column u se d .

With a column which

had b een used v e r y l i t t l e , and w ith th e column a t room tem p eratu re, th e
i n j e c t i o n o f Q.Q1 m l. o f methane produced a resp on se w ith a s i g n a l - t o n o is e r a t io comparable t o t h a t obtained w ith ou t th e column.

As th e

column was h e a te d , how ever, th e background cu rren t and n o is e in crea sed in
th e d e t e c t o r .

T h is e f f e c t was v e r y much worse w ith a column which had

b een used f o r a lo n g tim e w ith th e e f f lu e n t a t atm ospheric p r e s s u r e .
I t i s b e lie v e d t h a t u sin g th e column w ith reduced p r e ssu re r e s u lt e d in
f r e e in g h ig h b o i l i n g r e s id u e s in th e column.

The r e s id u e s were from

p re v io u s sam ples run through th e column a t h igh er p r e ssu r e s, and perhaps
a l s o breakdown p roducts from th e column i t s e l f .

The a d d itio n o f a

137

,o

°5

^r \
c3°

20
O
it
o

in

L±J

Ckz

o
o

c

UJ
CL

X

<x
o
C£
o

o
Cl_

O

o

O
o
♦Ik

c?

INJECTION

INJECTION

—

4MINj<—

FIGURE 1 6 ,
C H R O M A T O G R A M S USING T H E T E S L A D I S C H A R G E
D E T E C T O R 3 AR (+Cfc) C A R R I E R , O N E M E G O H M R E S I S T O R ;
E L E C T R O D E , i l N . 3 6 F T . PACKED C O L U M N .
A.
B.

0 .2 5 M L

NATURAL

GAS,

7 3 ° G,

NOISE

1.0 M L. OF VAPOR ABOVE A SOLUTION
2 0 M L. BENZENE AND 2 M L . OF EACH
OTHER COMPONENTS;
1 0 0 ° C , NOISE

LEVEL 0 . 0 2 / * a
CONTAINING
OF THE
LEVEL 0 . 0 3 / n a .

138

p res su re-d ro p p in g c a p illa r y in th e e f f lu e n t s id e o f th e column would
m inim ize t h i s d i f f i c u l t y .

The column could th en be used w ith th e e f f lu e n t

a t atm osp h eric p r e ssu r e , which would a ls o be advantageous f o r stream —
s p l i t t i n g o p e r a tio n w ith p re p a ra tiv e colum ns.
The chromatogram d e p ic te d in F igu re 1633 was ob tain ed from a one —
m i l l i l i t e r i n j e c t i o n o f th e vapor above a s o lu t io n prepared from 20 m l.
b en zen e, and 2 m l. each o f n -hexane, a c e to n e , cyclohexane and carbon
te tr a c h lo r id e .

T h is tr a c e was made a t 100° Cyand th e n o is e l e v e l was

s l i g h t l y h ig h er th an in th e p rev io u s chromatogram o f n a tu r a l gas, which was
made a t 73°

T his chromatogram i s in clu d ed m erely t o show th a t th e

d e t e c t o r i s s e n s i t i v e to a v a r ie t y o f su b sta n ces which are o f g en e r a l
i n t e r e s t in vapor phase chrom atographic work.

S in c e th e T e sla c o i l output

i s a v e r y h ig h v o lta g e , capable o f io n iz in g a l l m o le c u le s, th e d e t e c to r i s
u n iv e r s a l in i t s r e sp o n se .
d . I n flu e n c e

o f D e te c to r Geometry on S e n s i t i v i t y

Only th e two

m o d ific a tio n s of th e t e e tube which were d escrib e d in

th e apparatus s e c t io n were stu d ied in d e t a i l .

These two forms o f th e

d e t e c t o r d if f e r e d m ainly in th e area o f th e e le c t r o d e s , both in n er and
o u te r .

The second form o f th e d e t e c t o r , which had a l / 8 - i n .

in n er

e le c t r o d e w ith a p p roxim ately 6 mm. in n er diam eter o f th e t e e , was 3 t o 6
tim e s as s e n s i t i v e f o r a i r or argon c a r r ie r , r e s p e c t iv e ly , as th e e a r l i e r
form o f th e d e t e c t o r , which had a l / l 6 “i n . in n er e le c tr o d e and lj. ram.
in n er d iam eter o f

th e t e e .

In c r e a sin g th e s i z e o f th e t e e tu be fu r th e r

could p o s s ib ly r e s u l t in fu r th e r in c r e a s e in s ig n a l .

Karmen and Bowman

(6 U ), u s in g a r a d io fr eq u e n c y v o lta g e a p p lied d i r e c t l y t o th e in n er

139

e le c t r o d e as ex c i t a t io n f o r 'th eir glow d isch a rg e d e t e c t o r , r e p o rt t h a t
th e in t e r n a l r e s is t a n c e o f th e c e l l in c r e a s e s m arkedly when th e diam eter
o f th e o u ter e le c t r o d e exceed s I/J 4. i n .

They rep o rt u s in g o n ly a t h in

in n er w ir e e l e c t r o d e ,0 .0 2 i n . in d iam eter.

I n a d d itio n t o t h i s , t h e ir

ra d io fr eq u e n c y e x c i t e r ap p a ren tly did n o t reach th e extrem es o f v o lt a g e
employed h e r e , b eca u se th e y could not e x c it e an argon d isc h a r g e r e a d i ly .
I t would seem w o rth -w h ile, th en , t o in v e s t ig a t e th e p r o p e r tie s o f d e t e c to r
c e l l s w ith la r g e r e le c t r o d e s u r f a c e s .
a . Summary
The e l e c t r i c a l form o f th e T e sla d isc h a r g e d e t e c to r f o r gas chroma­
tograp h y h as been shown to be s e n s i t iv e t o l i g h t g a ses w ith high i o n iz a t i o n
p o t e n t ia ls , as w e l l as th o se m o lecu les o f low er io n is a t io n p o t e n t ia l t o
w hich o th e r d e t e c to r s commonly in u se are s e n s i t iv e .

The d e te c to r has

been found t o be most s e n s i t i v e t o hydrocarbons when argon i s th e c a r r ie r
g a s , alth o u g h th e s e n s i t i v i t y t o hydrocarbons w ith a ir or n itr o g e n c a r r ie r
i s adequate f o r d em on stration purposes or p rep a r a tiv e chrom atographic worku sin g a sim p le raicroammeter as an in d ic a t o r .
U sing an a i r c a r r ie r , h e liu m -a ir m ixtures in th e range O-I4.O volume
p e r c e n t can be an alyzed t o w it h in a few p e r c e n t.

The d e t e c to r w ith a i r

c a r r ie r shows s u f f i c i e n t s e n s i t i v i t y t o w ater vapor in a ir t o be used
f o r h u m id ity m easurem ents.
U sin g argon c a r r ie r w ith an oxygen sca v en g er, th e resp on se t o 0 .0 1
m l. methane was a t a s ig n a l - t o - n o i s e r a t io o f about 1300 (T able V I I ) .
Assuming l i n e a r resp o n se o f th in d e te c to r t o methane in j e c t io n s below

iU o

0*01 m loj which seems rea so n a b le from th e s t r e a m - s p lit t in g experim ent*
th e lo w er l i m i t o f s e n s i t i v i t y * based on a s ig n a l- t o - n o i s e r a t i o o f 2*
=9
„a
i s 0*7 x 10
m oles or 3 x 10
grams o f methane* This v a lu e would be
a p p ro x im a tely h a lv ed f o r h e a v ie r hydrocarbons* r e s u lt in g i n a l i m i t o f
d e t e c t a b i l i t y f o r C3 and h ig h er m olecu lar w eigh t compounds o f c lo s e t o
10

grams* The lo w er l i m i t o f d e t e c t a b i l i t y g e n e r a lly taken f o r a
a8
k atharom eter i s
10
grams* The d e te c to r a t t h is s ta g e o f developm ent
th en appears a t l e a s t as s e n s i t iv e i n th e low c o n cen tra tio n range* and
may a c t u a ll y be s l i g h t l y more s e n s it iv e than a katharometer*

The T e sla

d isc h a r g e d e te c to r * however* w i l l s a tu r a te a t tw o-p ercen t co n cen tr a tio n s
o f o rg a n ic vapor w h ile th e katharom eter does not s a tu r a te a t a l l*
I t seems q u ite p robable th a t th e s e n s i t i v i t y o f th e d e t e c to r could
be in c r e a se d a p p re cia b ly by ap p rop riate d e sig n o f th e te e -t u b e s e n sin g
ele m e n t»
f * I n t e r p r e t a tio n o f E l e c t r i c a l D e te c to r Response
The p r in c ip le o f o p era tio n o f th e T esla- e x c ite d glow -d isch arge
e l e c t r i c a l d e t e c to r seems t o be v e r y c l o s e l y r e la te d t o th e e f f e c t
d e sc r ib e d i n r e c e n t papers by Ghenot (6 6 ) and L ion (6 ? ) as occu rrin g i n
a ra d io fr eq u e n c y glow d isch a rg e*

The s im p le st form o f th e e l e c t r i c a l

c i r c u i t used i s i l l u s t r a t e d in F igu re 17*

I t was observed t h a t when two

e le c t r o d e s A and B s e a le d in a g la s s tube w ith a gas a t a few m illim e te r s
p r e ssu r e were p la ced betw een e x te r n a l e le c tr o d e s P x and P 2j through which
p assed a h ig h freq u en cy e l e c t r i c a l f ie ld *

a d«c* p o t e n t ia l d iffe r e n c e * E0*

appeared b etw een th e e le c tr o d e s i n th e s e a le d tube*

This p o t e n t ia l

11+1

d if f e r e n c e depended on th e p o s it io n s and shapes o f th e e le c tr o d e s and was
z e r o f o r a p e r f e c t l y sym m etrical arrangement*

L ion u t i l i z e d t h i s r a d io -

freq u en cy r e c t i f i c a t i o n e f f e c t to d evelop a m e c h a n ic a l- e le c t r ic a l

P

*1

F igu re 17*

A

A M e c h a n ic a l-E le c tr ic a l Transducer*

tran sd u cer, whereby m echanical m otion of th e e x te r n a l e le c tr o d e s r e s u lte d
in v a r i a t io n o f th e output v o lt a g e , E0 .

The v o lta g e Eq and th e s e n s i­

t i v i t y o f t h e system t o m echanical m otion o f th e e le c tr o d e s depend
s t r o n g ly on th e n ature and p ressu re o f th e gas in th e tu b e , and s l i g h t l y
on t h e freq u en cy o f th e so u rce v o lta g e betw een 3 and 10 m egacycles per
seco n d , and th e peak so u r ce v o lta g e *
Both Lion and Chenot have d escrib ed th e in ner e le c tr o d e s A and B as
probes in s e r te d i n t h e plasm a o f th e glow d isc h a r g e *

In a d.c* e le c t r ic a l

f i e l d , w ith a higjh impedance lo a d e x t e r n a lly between A and B, th e s e probes
would each assume a n e g a tiv e p o t e n tia l*

T his i s b ecau se th e e le c tr o n s

i n th e d isc h a r g e have much h ig h e r v e l o c i t i e s than do th e p o s it iv e io n s

m2

and a re c o lle c t e d on th e probes in e x c e ss o f th e p o s i t i v e i o n s *

Each

probe th e n w i l l a t t a i n a n e g a tiv e charge whose magnitude depends on th e
e le c t r o n and io n v e l o c i t i e s and co n cen tra tio n s i n th e r e g io n o f th e
plasm a where th e probe i s lo c a te d * Asymmetrical lo c a t io n o f th e s e probes
in t h e e l e c t r i c a l f i e l d th en r e s u lt s in a d iff e r e n c e in p o t e n t ia l
betw een th e probes ( e le c t r o d e s ) A and B*
With a lt e r n a t in g cu rren t th e p ic tu r e i s com plicated* b ecau se A and
B are u n a v o id a b ly coupled c a p a c it iv e ly t o th e e x c it e r e le c tr o d e s P 3. and
P2 .

The r e s u lt i s t h a t th e p o t e n t ia ls of th e e le c tr o d e s A and B o s c i l l a t e

p e r i o d i c a l l y w ith th e in p u t v o l t a g e *

The o s c i l l a t i n g p o t e n t ia l i s ,

how ever, an asymm etric one which can be r e s o lv e d r e a d ily in t o an
o s c i l l a t i n g component and a d„c* component by a s u it a b le f i l t e r i n g
c ir c u it* .

The output from th e e le c tr o d e s A and B i s asym m etrical, even

though th e p o t e n t ia l coupled t o th e probes i s a sym m etrical on e, b ecau se
t h e r e i s a p r e fe rr ed d ir e c t io n f o r cu rren t flo w between th e probe and
plasma*

E le c tr o n s , w ith t h e ir h ig h er v e l o c i t i e s , p e n e tr a te a r e ta r d in g

p o t e n t i a l sh ea th about th e probe much more r e a d ily than th e l e s s m obile
p o s i t i v e io n s can p e n e tr a te a r e ta r d in g p o t e n t ia l ( 6 9 )0

The r e s u lt i s

t h a t when a probe has a c e r t a in n e g a tiv e p o te n tia l, t h is i s much l e s s
e f f e c t i v e i n k eep in g th e probe from c o l l e c t i n g e le c tr o n s than a p o s it iv e
p o t e n t i a l o f th e same m agnitude would be in r e p e llin g p o s i t i v e io n s*
S in c e e le c t r o n s a re captured more r e a d ily than p o s it iv e io n s a t
th e p r o b e s, th e r e r e s u l t s , as in th e example u s in g a u n id ir e c t io n a l
a p p lie d f i e l d , a n e t n e g a tiv e charge on th e probes, th e magnitude o f which
depends on t h e p o s it io n o f th e probes in th e e l e c t r i c a l f i e l d betw een

1 k3>

"the e x t e r n a l ele ctr o d es®

A d 0c® component o f p o t e n t ia l i s p resen t betw een

th e probes e x ce p t when th e y are sy m m etrica lly p la ced in th e e l e c t r i c
fie ld ®

The probe e le c t r o d e which was n earer an e le c tr o d e o f th e in p u t

so u r ce was in v a r ia b ly n e g a tiv e w ith r e s p e c t t o th e oth er more remote
probe electro d e®

The p o l a r i t i e s o f th e output v o lta g e E0 i n Figure 17

i l l u s t r a t e t h i s fact®
The c h a r a c t e r i s t i c s o f th e T e sla -d isc h a r g e e l e c t r i c a l d e te c to r
observed so f a r appear., q u a lit a t iv e ly * v e r y s im ila r t o th e p r o p e r tie s
observed b y L ion f o r th e m e c h a n ic a l- e le c t r ic a l transducer®
The s e n s i t i v i t y o f th e tran sd u cer (d®c® v o l t s output per m il
t r a n s la t io n o f e le c t r o d e ) was found to depend on th e p r e ssu re o f th e gas
i n th e s e a le d tu b e as w e l l as th e nature o f th e gas®

The maximum

s e n s i t i v i t y u s in g argon gas occurred a t about 25 mm® p ressu re, w h ile t h a t
f o r h eliu m occurred a t about 90 mm® pressure®
th e same magnitude®

These maxima were o f about

The s e n s i t i v i t y maximum f o r a neon tran sd u cer was

f i f t y p e r c e n t g r e a te r th an f o r argon and helium and occurred a t about 10
mm® p ressu re* b u t th e maximum f o r neon was broader than f o r argon or
heliu m ®
In th e T e s la d isc h a r g e d etecto r* th e d e te c to r cu rren ts f o r argon
and h eliu m c a r r ie r have b een found to have maxima a t p ressu res c lo s e t o
th o s e found b y L io n t o produce maximum resp on se o f th e transducer®
The in c r e a s e in s e n s i t i v i t y o f th e e l e c t r i c a l d e te c to r t o hydro­
carbons* which was observed when oxygen was allow ed t o b le e d s lo w ly in to
th e sy stem below th e e x c it e r tube^was unexpected and has not been e x p la in e d .

ih h

The s t a b i l i t y o f th e argon d isch a rg e has b een a ttr ib u te d t o th e abundance
o f m e ta sfa b le argon atoms i n th e discharge^ which keep io n iz a t io n p r o c e s se s
g oin g "when th e h ig h freq u en cy e x c it a t io n goes through th e low v o lta g e
p o r tio n o f i t s c y c l e «
The h ig h s e n s i t i v i t y * based on th e s ig n a l- t o - n o is e r a tio * found f o r
th e T e s la d isc h a r g e d e t e c to r s w ith argon carrier^ were due l a r g e l y t o t h i s
s t a b i l i t y o f th e d isch a rg e* which r e s u lt e d in a low n o is e l e v e l compared
t o a i r or n it r o g e n *
F* Comparison o f th e Photom etric and E l e c t r ic a l
T e s la D isch arge D e te c to r s
lo S e n s it iv it y
Both th e g r e e n - s e n s it iv e p hotom etric and th e e l e c t r i c a l form o f th e
T e s la d isc h a r g e d e t e c to r f o r gas chromatography have been shown t o respond
w ith a p p roxim ately eq u a l s e n s i t i v i t y t o sm a ll hydrocarbon sam ples (T able
V II) i n t h e i r p r e s e n t forms * Both can be improved in t h e ir s e n s it iv it y *
as h as a lr e a d y b een su g g ested *
2 * R e te n tio n Volume
B ecause th e d e t e c to r s are operated a t reduced p ressu re* th e apparent
r e t e n t io n or dead volume o f e it h e r d e t e c to r i s estim a ted t o be r e l a t i v e l y
low* determ ined m ain ly b y th e diam eter o f c a p illa r y chosen f o r th e e x c i t e r
tube*

The s e n s in g elem en ts c o n tr ib u te n e g lig ib le volume*

The c o n d u c tiv ity

o f t h e t e e -t u b e d e t e c to r depends m ainly on th e r e g io n betw een th e end o f
th e in n e r e le c t r o d e and th e c a p illa r y tube*

This volume i s n e g lig ib l e

compared w ith th e volume o f th e c a p illa r y i t s e l f «

The l a t t e r i s about

11*5

50 m ic r o lite r s^ which, a t a reduced p ressu re o f a few m illim e te r s o f m ercury

r e s u l t s i n an apparent volume o f about 0*1 m ic r o lit e r s *

Thi s i s adequate

f o r c a p i l l a r y column work*
3* L in e a r it y o f Response
E xperim ents have a lre a d y in d ic a te d t h a t th e resp on se curve f o r th e
e l e c t r i c a l d e t e c to r w ith argon c a r r ie r i s lin e a r f o r methane in j e c t io n s
below 0*01 ml*

Such in fo r m a tio n has not y e t been determ ined f o r th e

p h otom etric d e te c to r *

With a i r c a r r ie r th e resp on se o f th e e l e c t r i c a l

d e t e c to r i s l i n e a r up t o about o n e-p ercen t hydrocarbon c o n c e n tr a tio n s ,
and much h ig h e r f o r hydrogen and helium*
k* C a r r ie r Gases
Both d e t e c t o r s re q u ir e argon c a r r ie r gas f o r t h e ir most s e n s i t iv e
o p e r a tio n y e t observed and w i l l r e q u ir e an oxygen scavenger f o r work w ith
“macro® sam ples*

A y e llo w - s e n s it iv e photom etric d e te c to r u sin g th e

quenching o f t h e s tr o n g y e llo w arc l i n e i n th e spectrum o f h elium c a r r ie r
gas may be h ig h ly s e n s i t i v e , but a ls o would probably req u ire a scavenger*
A ir or n itr o g e n may be used w ith e it h e r d e te c to r f o r p r e p a r a tiv e or
d em on stration work w ith la r g e r samples*
Die g r e e n - s e n s it iv e p h otom etric d e t e c to r showed l i t t l e s e n s i t i v i t y
t o a i r and cou ld th e r e fo r e be used t o d e t e c t hydrocarbons sampled i n a i r ,
w h ile t h e e l e c t r i c a l d e t e c to r co u ld not b e so used*

The e l e c t r i c a l

d e t e c to r u s in g a i r c a r r ie r i s , how ever, s e n s i t iv e enough t o cover some
s im ila r a p p lic a tio n s *

1hS

$* S e l e c t i v i t y
Both d e t e c t o r s a re u n iv ersa l, in t h e ir response* but th e p hotom etric
d e t e c t o r has added p o s s i b i l i t i e s f o r c o n tr o lle d s e l e c t i v i t y by c o n tr o l
o f w a v elen g th s observed#

This could prove advantageous i n c e r t a in a p p l i - -

c a tio n s where th e d e t e c t io n o f s p e c i f i c sample su b sta n ces in th e c a r r ie r
i s d e sir e d #
G-. S u g g e stio n s f o r A p p lic a tio n s and Further Work
1# L ectu re D em on stration and P r ep a ra tiv e Work
A number o f i n t e r e s t i n g a rea s f o r fu r th e r work u sin g th e T e sla
d isc h a r g e d e t e c to r have been su g g ested b y th e r e s u lt s o f th e p r e se n t
in v e s t ig a t io n *

Some o f th e s e areas have b een mentioned b r i e f l y i n

p re v io u s s e c t io n s and w i l l b e review ed or extended h ere alon g w ith oth er

E ith e r th e p h otom etric or e l e c t r i c a l form o f th e d e te c to r has b een
shown s e n s i t i v e enough and o f s u f f i c i e n t ea se o f c o n s tr u c tio n from in ­
ex p en siv e components t o b e g e n e r a lly a p p lic a b le t o le c t u r e d em onstration
o f gas chromatography and t o p rep a r a tiv e chrom atographic work*

With

argon or h eliu m c a r r ie r * th e p h otom etric d e te c to r may be used a t atmos­
p h e r ic p r essu re*

The p h otom etric d e te c to r in i t s s im p le st form appears

t o b e a sm a ll d iam eter c a p illa r y tu b e i n which are lodged two w ire
e le c tr o d e s * w ith aluminum f o i l wrapped around th e o u tsid e o f th e tu be
in th e v i c i n i t y o f each in t e r n a l e le c tr o d e *

The T e sla c o i l output goes

t o one p ie c e o f aluminum f o i l and i s th en ce coupled t o th e w ire* th e
o th er w ir e jd owns t r earn>c o u p les th e d isch a rg e t o th e oth er f o i l * and th en ce

XU?

t o ground <> A p h o t o c e ll may be attach ed t o the d isc h a r g e tu b e , as in
t h i s w ork, t o r e c e iv e l i g h t from th e d isch a rg e betw een th e in n e r e le c t r o d e s ,
or th e v i s u a l in d ic a t io n may be used#

I f th e d e t e c to r i s operated a t

reduced p r e s s u r e , a i r or n itr o g e n c a r r ie r gas may be used*

At atm ospheric

p r e ssu r e t h e s e g a ses g iv e spark ra th er than glow d is c h a r g e s , b u t even
t h e s e can b e used®

For v i s u a l dem onstrations i t may be d e s ir a b le t o u se

a l a r g e r - s i z e d c a p illa r y tu b e , so t h a t changes in th e em issio n spectrum
may be observed a t lo n g e r d ista n c e s*
For m o n ito rin g a p r e p a r a tiv e column, any o f th e v a r ia t io n s o f th e
d e t e c t o r d e sc r ib e d may be ch osen , depending on c a r r ie r gas and s e n s i t i v i t y
requirem ents®

To s im p lif y th e s t r e a m - s p lit t in g apparatus and c o l l e c t i o n

o f p r o d u c ts, i t seems p r e fe r a b le t o op erate w ith th e chrom atographic
column e f f l u e n t s l i g h t l y above atm ospheric pressure®

This i s r e a d ily

accom plished i f th e p h otom etric d e te c to r w ith argon or helium c a r r ie r i s
u se d , b eca u se t h e d e t e c to r can oparate e f f e c t i v e l y above atm ospheric
pressure®

I f th e e le c t r ic a l, d e t e c to r i s t o b e u sed , i t must be a t reduced

pressure®

The d e t e c to r can be operated a t reduced p r e ssu r e w ith i t s

in ta k e s l i g h t l y above atm ospheric p ressu re w h ile em ploying a chrom atographic
column by in tr o d u c in g a f lo w - lim it in g c a p illa r y a f t e r th e column and
b e fo r e th e e x c i t e r tube®

The p r e ssu re a t th e in p u t t o th e column can th e n

be s e t f a r enough above atm ospheric t h a t s e v e r a l pounds p er square in ch
p r e s su r e i s dropped a cro ss th e column, and i t s output t o th e flo w li m i t e r
(b e fo r e th e d e t e c t o r ) i s s l i g h t l y above atmospheric®

The stream may then

be s p l i t e a s i l y betw een th e column e x i t and th e f lo w - lim it in g c a p illa r y
b y u se o f a t e e tu b e , w ith th e major p o r tio n o f th e stream e x i t in g t o a

m8

tra p f o r p r e p a r a tiv e work <> The s p l i t t i n g r a t io may be a d ju sted b y a
n e e d le v a lv e in an arm o f th e t e e carryin g th e major p o r tio n o f th e
column e f f l u e n t o
2o H um idity Measurements
H um idity measurements have been shown f e a s i b l e w ith th e e l e c t r i c a l
d e t e c to r u s in g a ir as a c a r r ie r g a s .

I t i s a ls o p o s s ib le t h a t th e photo­

m e tr ic d e t e c t o r u sin g a i r or an in e r t gas as a c a r r ie r could be employed
t o d e t e c t w a ter v a p o r.

The red atom ic l i n e o f hydrogen (H ) appears
CL

v e r y s tr o n g ly in th e d isc h a r g e a t 6 5 6 .3 m illim ic r o n s .

A r e d - s e n s it iv e

p h o t o c e ll could be used t o m onitor t h i s p o r tio n o f th e spectrum .

With a

s u i t a b l y narrow-bandpass f i l t e r b e fo r e th e p h o t o c e ll, i t may be p o s s ib le
t o u se an i n e r t gas c a r r ie r and a ch iev e g rea ter s e n s i t i v i t y and a ls o be
a b le t o o p er a te th e d e t e c to r a t atm ospheric p r e s s u r e .

The f i r s t - p o s i t i v e

e m issio n band system o f n itr o g e n appears in th e red p o r tio n o f th e
spectrum (band heads a t 65U°U and 662 .U m illim icrons}, but th e s e bands do not
obscure th e hydrogen l i n e .
3® Vapor P r e ssu r e and M olecular W eight D eterm ination
The T e sla d isc h a r g e d e te c to r a ls o may prove a p p lic a b le t o organic
vapor p r e ssu r e and m o lecu la r w eig h t d e term in a tio n .

The sam pling tech n iq u e

employed could be s im ila r t o t h a t used in t h is work to sample organ ic
l i q u i d s - - ! . e . , s a tu r a tin g a stream o f th e c a r r ie r gas w ith th e liq u id a t
a p a r t ic u la r tem p era tu re, and th en in j e c t in g t h is m ixture, or d ilu t io n s
o f i t , i n t o th e d e t e c t o r .

V a r ia tio n s in vapor p ressu re o f a v o l a t i l e

s o lv e n t in th e p resen ce o f a n o n - v o la t ile s o lu t e would b e r e f le c t e d by

1U9

changes in "the c o n c e n tr a tio n o f ■the s o lv e n t in th e c a r r ie r gas and be
measured by th e resp o n se o f th e d e t e c to r .
k » Q u a lit a t iv e A n a ly sis
a« G eneral
Q u a lit a t iv e a n a ly s is o f components d e te c te d in a gas chromatogram
has n o t k ep t pace w ith th e developm ent in se p a r a tin g power o f th e columns.
A c o n v e n ie n t g e n e r a l method f o r id e n t i f i c a t i o n o f components i s d e s ir a b le .
The T e sla d isc h a r g e d e t e c t o r , as has a lrea d y been m entioned, o f f e r s some
prom ise a lo n g t h i s l i n e .

Sim ple v i s u a l o b se r v a tio n o f th e d isch a r g e w ith

a sm a ll s p e c tr o sc o p e i s cap able o f on ly lim ite d d i f f e r e n t i a t i o n o f com­
p o n e n ts, as dem onstrated in an e a r l i e r s e c t io n , but i t i s known from
o b se r v a tio n s in P a rt I o f t h i s work, th a t f in e r d is t in c t io n s betw een
compounds in th e d isch a rg e can be made r e a d ily w ith a spectrop h otom eter.
D e t e c t io n o f h etero -a to m s by th e appearance o f d iatom ic fragm ents
c o n ta in in g th o s e atoms in th e d isch a rg e appears q u ite f e a s i b l e and has
a lr e a d y b een d is c u s s e d e a r l i e r .

D e te c tio n o f more s u b tle s t r u c t u r a l

d if f e r e n c e s r e q u ir e s more e x p lo r a tio n than has been done.

From th e

o b se r v a tio n s in P art I , i t was found th a t a lc o h o ls could be d if f e r e n t ia t e d
from a ce to n e in th e glow d is char ge^ because th e r a t io o f th e i n t e n s i t y o f
th e OH e m issio n spectrum t o th a t o f GO was a p p recia b ly h ig h er f o r th e
a lc o h o ls .
In order t o o b ta in s u it a b le i n t e n s i t y f o r d e t a ile d a n a ly s is o f th e
d is c h a r g e , i t may be n e c e s sa r y to view a p o r tio n o f th e d isch a rg e tube
en d -o n .

This can be accom plished r e a d ily in a number o f w ays.

A tee —

150

shaped capi l l a r y tu b e in trod u ced in to th e d e te c to r system betw een th e
e x c i t e r tu b e and th e grounded e le c tr o d e o f th e d e te c to r could be used •
The arm o f th e t e e in l i n e w ith th e e x c i t e r w ire can be ground o f f t o
m inim ize any dead volum e introduced* and a t h in window (p r e fe r a b ly
q u a rtz) can be waxed on th e r e f o r s p e c tr a l ob servation *

The c e n te r arm

o f th e t e e th en would be s e a le d w ith an w0 11 r in g in t o th e b ra ss tee* as
had b een done w ith th e e x c it e r tube w ith ou t th e c a p illa r y o b se rv a tio n t e e .
b * Rapid Scanning Spectrophotom eter
Rapid d is p la y o f th e T e s la -d is c h a r g e -e x c ite d e m issio n spectrum o f
chrom atographic components w ith r e la t iv e i n t e n s i t i e s o f th e s p e c t r a l peaks
would be ex trem ely u s e f u l in o b ta in in g s t r u c t u r a l in form ation about th e
com ponents.

T his d is p la y could be s e t up by fe e d in g th e output from a

r a p id ly scan nin g spectrop h otom eter t o th e v e r t i c a l d e f le c t i o n p la t e s o f
an o s c i l l o s c o p e .

The h o r iz o n ta l tr a c e would be synchronized w ith th e

sp ectrop h otom eter scan o f th e s p e c t r a l r e g io n o f i n t e r e s t .
c . T e s la D isch a rg e Cracking
An i n t e r e s t i n g arrangement which m ight e f f e c t q u a lit a t iv e i d e n t i f i ­
c a t io n o f gas chrom atographic components i s based on u sin g th e T esla
d isc h a r g e d e t e c to r in a way s im ila r in nature t o th e u se o f th e mass
sp ectro m eter t o a n a ly ze th e sep arated f r a c t io n s from a gas chrom atographic’
s e p a r a tio n .

The output from a f i r s t chrom atographic column can be fed

in t o th e T e s la d isch a r g e d e te c to r In th e normal manner, le a d in g t o th e
u su a l d e t e c t io n and cra ck in g o f each component.

As components come through

th e d e t e c t o r , th e d e t e c to r e f f lu e n t f o r each component could be routed

151

in t o a s e p a r a te a d d it io n a l column.
fe e d in t o i t s own d e t e c t o r .

Each o f th e s e secondary columns would

The l a t e r columns would s e r v e t o sep a r a te

th e v a r io u s su b sta n c e s formed by de compos i t io n in th e cou rse o f p assage
o f th e o r i g i n a l s i n g l e component through th e T esla d isch a rg e * The crack­
in g p a tte r n o b tain ed f o r a component by a secondary column and d e t e c to r
would be somewhat anaiagous t o a mass s p e c tr a l crack in g p a tte m ^ in b e in g
a b le t o p ro v id e in fo rm a tio n on th e s tr u c tu r e o f th e o r ig in a l m o le cu le .
The p a tte r n ob tain ed w ith d ecom position by th e T esla d isch a rg e would be
com p licated by secon d ary r e a c tio n s o f th e fragm ents form ed, but could
w e l l be c h a r a c t e r is t ic f o r v a r io u s s tr u c t u r a l ty p e s o f m o le c u le s .
5° High M olecular W eight Compounds
H ig h -m o lecu la r-w eig h t compounds such as p l a s t i c s , h igh b o ilin g o i l s ,
etc

m ight a l s o b e c h a r a c te r iz e d w ith a chrom atographic column a t low

tem p eratu res by u sin g th e T esla d isch a rg e to fragm ent th e s e h ig h -b o ilin g
su b sta n c e s and th en running th e vapors produced through a gas chroma­
to g r a p h ic system o f a s u it a b le t y p e .

I n te r p r e ta tio n of t h e s e fragm en tation

p a tte r n s would fu r n is h s tr u c t u r a l in form ation about th e p aren t m o le c u le s.
I t would p rob ab ly be d e s ir a b le t o u se a c a r r ie r gas in th e d isch a rg e t o
h e lp fragm ent th e h ig h -m o lec u la r-w eig h t compounds by th e bombardment o f
th e compound w ith e x c it e d c a r r ie r gas atoms and i o n s .
Ho O v e r -a ll Summary o f E le c t r ic a l D e te c to r s
f o r Gas Chromatography
In view o f th e tremendous r e c e n t s u c c e ss o f gas chrom atographic
d e t e c to r s based on th e e l e c t r i c a l p r o p e r tie s o f g a s e s , i t now appears

15>2

d e s ir a b le t o c l a s s i f y th e e x i s t i n g d e te c to r s in term s o f th e fundam ental
p r o p e r t ie s th e y m easure3 and t o ex p lo re p o s s ib le fu r th e r a d a p ta tio n s o f
th e f in d in g s o f e le c t r o n p h y s ic is t s t o chrom atographic d e t e c t io n .
The f i r s t rep o rted io n iz a t io n d e te c to r was th a t o f H arley and
P r e to r iu s (6 3 )* who measured th e c o n d u c tiv ity o f a d .c . glow d isc h a r g e ,
u s in g a "Wheatstone b r id g e c i r c u i t w ith c a r e f u lly reg u la ted in p u t v o lt a g e .
The d e t e c t io n o f components i s based upon changes in number o f charge
c a r r ie r s due t o gas com p osition -in d u ced changes in f i r s t and second
Townsend c o e f f i c i e n t s and quenching or e le c t r o n capture p r o c e s s e s .
The io n iz a t io n gauge d e te c to r o f Ryce and Bryce ( 6 0 ) , extended by
l a t e r w orkers ( 6 5 ) , in v o lv e s measurement o f th e io n cu rren t a t low
p r e ssu r e u s in g a th erm io n ic e m itte r and a v o lta g e j u s t inad equ ate t o
i o n i z e th e c a r r ie r g a s .

Here a stream o f e le c tr o n s i s a c c e le r a te d up t o

a predeterm ined energy and bombards th e c a r rier-sa m p le g a s.

The cu rren t

i s dependent on io n iz a t io n p o t e n t ia ls and cr o ss s e c t io n s o f th e sample
m o le c u le s, and m easures th e number o f charge c a r r ie r s produced.
The argon io n iz a t io n d e te c to r o f Lovelock (6 2 ) employs a r a d io a c tiv e
e m itte r and a h ig h d . c . p o t e n t ia l t o p rovid e a source o f io n s and a
means o f m easuring io n c u r r e n t, even a t atm ospheric p r e s s u r e .

U sing argon

c a r r ie r gas n ear atm ospheric p r e s su r e , th e e le c t r o n energy i s la r g e ly
d is s ip a t e d in e l e c t r o n i c e x c i t a t io n , p a r t ic u la r ly to g iv e m eta sta b le
atom s.

The m e ta sta b le s th em selves can combine to g iv e some io n iz a t io n ,

but o n ly a sm a ll cu rren t i s ob tain ed in th e absence o f f o r e ig n g ases o f
low enough io n iz a t io n p o t e n t ia l t o be io n iz e d by th e m eta sta b le atom s.
When such g a ses are p r e s e n t, th e r e s u lt a n t io n iz a t io n in c r e a s e s th e

153

p o p u la tio n o f charge c a r r ie r s , which become a c c e le r a te d t o cause fu r th e r
e x c i t a t i o n and io n iz a tio n * s o th a t an a p p recia b le in c r e a s e in current i s
observed f o r a sma l l amount o f sample * The d ir e c t e x c it a t io n o f th e
argon t o th e m e ta sta b le l e v e l by e le c t r o n impact and th e io n iz a t io n b y
ra eta sta b les (Penning e f f e c t ) , are th e b a s ic p r in c ip le s employed in th e
L ovelock d e te c to r *
The flam e io n iz a t io n d e te c to r o f McWilliam and Dewar (61) employs
somewhat d i f f e r e n t p r in c ip le s *
o f hydrogen in oxygen.

The source o f e x c it a t io n i s th e com bustion

The e le c tr o n and io n c o n cen tra tio n in th e flam e

becomes abnorm ally h ig h w ith th e p resen ce o f ca rb o n -co n ta in in g compounds,
a p p a re n tly through th e advantageous f r e e energy c o n tr ib u tio n o f carbon
d io x id e fo r m a tio n t o in c r e a s e th e eq u ilib riu m e le c t r o n c o n c e n tr a tio n ( 7 0 ) *
The p r e se n t T e sla -d isc h a r g e e l e c t r i c a l d e te c to r and th e ra d io freq u en cy d e t e c to r o f Karmen and Bowman (6U) each u t i l i z e th e cu rren t or
v o lta g e produced b y th e glow d isch a rg e a cro ss probes asym m etrically lo c a te d
in th e d is c h a r g e .

As in th e d e te c to r o f H arley and P r e to r iu s , th e s e

d e t e c to r s g iv e resp o n se dependent upon a v a r ie t y of f a c t o r s .

Changes in

co m p o sitio n a l t e r th e number and nature o f th e charge c a r r ie r s , which
may be ex p ressed through changes in th e f i r s t Townsend c o e f f i c i e n t .

The

a c t u a l s ig n a l ob tain ed depends upon th e p r e f e r e n t ia l pickup o f e le c tr o n s
r a th e r th a n p o s i t i v e io n s a t th e p rob e, and upon th e asym m etrical lo c a t io n
o f th e two e l e c t r o d e s .
The T e sla d isch a r g e p h otom etric d e t e c to r , w h ile n ot d i r e c t l y measur­
in g e l e c t r i c a l p r o p e r tie s o f g a s e s , u t i l i z e s v ery s im ila r p r in c ip le s in
i t s o p e r a tio n .

The e le c t r o n impact and r e la te d p r o c e s se s which g iv e

151;

r i s e t o th e e l e c t r i c a l s ig n a l a ls o determ ine th e l i g h t emission*.

The

p h o to m etric d e t e c t o r , how ever, has one u n iq u ely im portant p r o p e r ty * -its
u se f u r n is h e s more than one p ie c e o f in form ation f o r a given gas compo­
s i t i o n , b eca u se th e i n t e n s i t y o f em issio n can be determ ined a t d if f e r e n t
s e le c t e d w a v elen g th s c h a r a c t e r is t ic o f in d iv id u a l components or c la s s e s
o f components *> I t i s p a r t ic u la r ly easy to d if f e r e n t ia t e , betw een p r o p e r tie s
o f c a r r ie r and sample gases*.

The d e te c to r output i s su b je c t to c o n sid er­

a b le a m p lif ic a tio n e x te r n a l t o th e d isch a rg e system through th e u se o f
p h o to m u ltip lie r s , so th a t i t i s , in p r in c ip le , capable o f d e t e c tin g a
s i n g l e m o lecu le a t th e u ltim a te s e n s i t i v i t y , though t h is i s , o f co u rse,
f a r from a r e a l i s t i c goal*.

In i t s u ltim a te form i t can in v o lv e a scanning

sp ectrop h otom eter capable o f fu r n is h in g in form ation from perhaps th e n ea rin fr a r e d t o th e vacuum u l t r a v i o l e t , and can g iv e evid en ce on e m ittin g
s p e c ie s , capable even o f d i f f e r e n t ia t in g between e x c ite d s t a t e s o f th e
e m it t e r •

C o n sid era b le fu r th e r work on th e c h a r a c te r iz a tio n o f components

through d isc h a r g e -e m iss io n s p e c tr a under p a r tic u la r c o n d itio n s seems
h ig h ly d e s ir a b le .

Only a b r i e f b egin n in g towards t h is typ e o f stu d y has

b een a ch ieved in P a r t I .

Advances in sp ectrop h otom etric tech n iq u es and

s e n s i t i v i t i e s f o r t h i s ty p e o f a p p lic a tio n a ls o are d e s ir a b le .
The most f r u i t f u l paths f o r fu r th e r e x p lo r a tio n alon g r e la te d l i n e s
would seem to be th e f o llo w in g .

F i r s t , some o f th e su g g ested d evelop ­

ments o f th e p h otom etric d e te c to r w ith p h o to m u ltip lie r and scanning or
b e t t e r m onochrom atization seem e s s e n t ia l..

Second, b a s ic d ata must be

ob tain ed on th e e l e c t r i c a l p r o p e r tie s o f organ ic vap ors— most data on io n
m o b i l i t i e s , e le c t r o n attach m ent, recom bination c o e f f i c i e n t s , Townsend

155

c o e f f i c i e n t s , and breakdown v o lta g e s are r e s t r ic t e d t o in e r t gases and
a few v e r y sim p le m o le cu le s *

Third, th e a p p lic a tio n o f some o f th e

m easuring te c h n iq u e s o f e le c t r o n p h y sic s should be explored f o r chem ical
a n a ly s is , in c lu d in g such th in g s as breakdown v o lt a g e s and th e p rod u ction
o f e le c t r o n s f o r gaseou s c o n d u c tiv ity s tu d ie s b y means o f p h o t o e le c t r ic
em issio n from metals®

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2 c

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P t . a . £*1*1*8 (1 9 5 °).

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5 0 . “G atalog o f Mass S p e c tr a l Data ,®1 American Petroleum I n s t i t u t e ,
R esearch P r o je c t J4J4, N a tio n a l Bureau o f Standards No. 7 6 .
5 1 . L . F r i e d m a n a n d J . T u r k e v i c h , J . Am. C hem . S o c . , 7U« 1666 (1 9 5 2 ).
5 2 . G. S . C um m ings and W. B l e a k n e y , P h y s. R ev ., j?8 , 787 (19UO).
53* D . F r o st and G. McDowell, P ro c. Roy S o c . (London), A2Ul, 19 U (1957)*
5U* “RCA Tube Handbook HB3, 11 Radio C orporation o f America, H arrison ,
New J e r s e y .
5 5 . R. P e a rse and A. Gaydon, “The I d e n t if ic a t io n o f M olecular S p e c tr a ,1*
2nd e d . , J . W iley and S on s, New York, 1950.
5 6 . Ho K ayser, A stro p h y s. J . , j 6 , 551 ( I 8 9 6 ) .
57* G. H a rriso n , “M assach u setts I n s t i t u t e o f Technology W avelength
T a b les , 11 J . W iley and S on s, I n c ., New York, 1939.
5 8 . H. O lsen and W. Huxford, P h ys. R ev ., 8 7 * 922 (1 9 5 2 ).
5 8 a . G. M. Almy, H. Q. F u lle r and G. D . K inzer, J . Ghem. P h y s ., 8 , 37
(19UQ) 3 M. S . M a th e s o n and J . W. Z a b o r , i b i d . . J.*
(1939)*
5 9 . T. E . Jordan, “Vapor P ressu re o f Organic Compounds, 11 I n t e r s c ie n c e ,
New York, 19514-.
6 0 . S . A. R y c e and W. A. B r y c e , Gan. J . C h e m ., 3 £ , 1293 (1 9 5 7 )6 1 . I . G. M c W iilia m a n d R. A* D e w a r , N a t u r e , l 8l , 76 O (1 9 5 8 ).
6 2 . J . E. L o v elo ck , J . Ghromatog. 1 , 35 (1 9 5 8 ).

159

6 3 . Jo H arley and Vo P r e to r iu s , N ature, 178 , 1214; (1 9 5 6 ).
6U«> ( a ) Ao Karmen and Ro L. Bowman, Ann., N. Y . Acad. S c i . , J 2j 71U (1 9 5 9 )j
(b ) Ao Karmert and R. L . Bowman, Instrum ent S o c ie t y o f America,
P r o c e e d in g s, 2nd B iannual I n te r n a tio n a l Gas Chromatography Symposium,
K e llo g g C en ter, M ichigan S t a te U n iv e r s ity , E ast L an sin g, .2,33 (1959)

6 5 o L» Vo G u ild , Mo Io Lloyd and F . A ul, Instrum ent S o c ie t y o f Am erica,
P r o c e e d in g s, 2nd B iannual I n te r n a tio n a l Gas Chromatography Symposium,
K e llo g g C en ter, M ichigan S t a t e U n iv e r s it y , E ast L ansing, 2 ,5 2 (1959)*
660 Mo C henot, J . p h y s. radium, 1^ 5U, 101 (1955)> i b i d . , ]& % k2

(1 9 5 6 ).

6 ?« K. So L io n , R ev. S c i . I n s t . , 2J, 222 (1 9 5 6 ).
680 Bo A. S i n c l a i r and R. N. W hittem, Sp ectrochim . A cta 1£, 168 (1958)*

6 9 . Ko G. Emeleus ^Conduction o f E l e c t r i c i t y Through G ases , 11 pp.
Jo W ile y , No Y . (1951)*
7 0 o Ho E y rin g , P r iv a t e Communication.

U0-U8,

160

TABLE XII
DETECTOR CURRENT v s 0 APPLIED VOLTAGEj AIR CARRIER
(One Megohm R e s is t o r , P » 3 06 mm., l / l 6 in* E le c tr o d e , Run 29b)
Data f o r Figure 8 „ _______________________
V o lta g e
A pplied

I fyia)

0

3*6

3

5*U

6

7 .8

1 0 .5

10*9

16 *5

15 o2

22

19*3

U5

35 *U

67

51*7

90

7 0 .8

161

TABLE X III
DETECTOR CURRENT v s . PRESSURE FOR N2> AIR* Ar AND He CARRIER GASES
(One Megohm R e sisto r* l / l 6 in* E lectrod e* Run 33)
Data fo r F igu re 9 .
N itro g en
1.3. p « S o io g 0
P(mm.)

1(^3.)

3 06

80 O

9 <>6

A ir

Argon
2 .5 p . s . i . g .

P(mm.)

I (/ia )

P(ram,)

I Qua.)

P(mm.)

iQxa.)

3*7

7 <>8

I4. .u

1 .2 0

k -3

3 .6

U-5
6

8 .2

7

9

U.o

9 .8

17

1*55
1.72

H;

U-8

17
22

5 .5

12 .0

23

12 o l

26

1106

10

1 1 .6

27

1 .8 2

32

12

1 2 .0

3k

1 .8 8

3k

9 -1
7 08

m

12 .6

U2

1 .7 2

39

U 08

17

1 2 .6

5U

1.U0

h2

3 -1
0.U0

23

11.7

6U

29

10 oU

0 „2Q

33

8.U

37

5*8

39

6 .9
8 .8

53

1 5 .8

75

1 .1 5
0 .9 0

79

19*8

91

0 .2 5

97
122

2 0 .1

152

1 5 .0

U6

U-7
2 .6

160

m .o

h9

1 .8

225

6 .6

51
60

0 .8

l.U

0.U5

309
370

65

0 .3 0

bk9

77

0

1 2 .1

CM
0

27
U8

0

9
18

5U
70

Helium
2 .5 P . s . i . g .

1 8 .6

0 .5 5
0 .2

162

TABLE XIV

RESPONSE TO 20 ML o INJECTIONS OF Hs , CH4 , AND He SOLUTIONS IN AIR,
AIR CARRIER, AS A JUNCTION OF PRESSURE
(One Megohm R e s is t o r , l / l 6 i n . E le c tr o d e )
Data f o r F igu res 10 and 11

3*3

U»6

k*7

&

k*2% CH^, Run 26b
P(mm)
A lQ ia.)
H
O

k 9 o3 Ho, Run 26a
A I(p u )
F(mm)

3 .6

li*8

1 1 .0

5*7

1 8 .7
2 0 .0

k*6

5 .2

11

8 .2

23 .5

8

Ik

9*7

25 *6

17

1 1 .0

2k

k9 *3% He, Run 25
P (mm.) ]C0(^a.) A I (pa.]
5 -1

- 2 .9

1 1 .8

U.5
6 .0

5*9

- 3 .2

7 .0

12 .8

9

7 .2

-3 *k

12

9 *k

H i. 8

13

9-3

- 2 .9

2 7 .0

21

25*5

15*1

16

10 .2

-2 .U

1 1 .1;

2 6 .3

35

8 .6

20

1 1 .1

32

8 .8

2 1 .5

k3

26

10 .3

- 1 .3
♦ 0 .8

36

7 *k

2 0 .2

6k

3*3
0 .3

6 .7
1 .0
0 .1

32

8 .6

♦ 3 -2

k2

li t . 6

37

6 .3

♦ 6 .2

50

3*7
0 .8

7 -9

5>B

0 .1

l.U

U3
U6

3 .1
1 .8

♦ 8 .3
♦10 .u

50

0 .9

5U

0 .3

♦ 1 0 .5
♦ 9 .8

77
116

0 .2
0 .1

♦ 1 .7
♦ 0 .1

163

TABLE XV
RESPONSE TO

20 M l. INJECTIONS OF H e , A r , H2 , CH4 AND N2
SOLUTIONS IN A IR ; AIR CARRIER

(O n e Megohm R e s i s t o r , I 0 «
u a , P .=
L a ta f o r F ig u re 1 2 .

Response ( A I , Microamperes)

C on een t r a t io n

(Volume P e r c e n t)

3 . 6 m m ., R un 2 9 a )

He

Ar

100 .0

-3 * 5

-U .6

8 8 .7

-3 -U

-U .o

7 8 .8

~3 -3

-3 .U
-3 .0

69 oQ

"3-3

- 2 .7

59 « l

~ 3 .0

- 2 .0

U9 .3

- 2 .8

“1 .5

73 >2

H2

ch4

- 1 .2

18 .8

- 0 .9

- 1 .1
-2.1;

- 0 .9
- 0 .7

29 <>6

«
H
*

00

h h '3

- 0 .5

21; *6

" 1.5

-Q.U

19 *7

- 1 .2

Hi .8

- 1 .0

9 -9

0 .7

1 2 .1

1 6 .6

U.9
2 0^

0 .3

8 .2

13 .h

3 9 .1;
3H .5

1 7 .1

9-U

1 .3
1 .0

3 .1

O08O

2 .3

5 .2

2 .7
2 .9

0 .6 5
0 .5 6

1 .2

O.32

0 .7

0 .1 7

N2

1.-3
0 .5

161;

TABLE XVI

RESPONSE TO 50 MLo INJECTIONS OF METHANE SOLUTIONS
IN ARGONj Ar(+02) CARRIER
(O cl Megohm R e sisto r* I 0 a lit Jia* P = 3«0 mm.* Run 33)
Data fo r Figure 13
C o n cen tra tio n CH4
(Volume P e r c e n t)

Response
A l( /ia )

1*83

15U

lo 2 6

137

0 .7 5

108

0 .2 1

29

0 .1 0

7.U

165

TABLE XVII
RESPONSE TO METHANE IN Ar(*Q2) CARRIER WITH 1 2 :1
STREAM SPLITTING RATIO
(One Megohm R e s is t o r , I 0 « 1 .5 jua, P ■ 2 ram., Run i|la )
B ata f o r Figure lit
Sample Volume
(Ml)

A I(/ia )

O.Q1

0.3 3

0*02

0 .8

Q.Qlt

2 .0 0

0 .0 5

lt.Q

Q «06

5*5

0 .0 8

8 .8

0 .1 0

11.2

0 .1 2

12 .8

0 . 1U

lit.G

0 .1 5

lit .5

0.2Q

16.7

0 .2 5

17 *9

166

TABLE XVTII
RESPONSE TO 50 ML • INJECTIONS OF AIR SOLUTIONS
IN ARGON; Ar(+02) CARRIER
(One Megohm R e s is t o r , I 0 * 1 .1 jia , and 0 .1 Megohm Re<
s i s t o r , I 0 a* 1 3 oQ jia , P « 2 .7 ram., Ran 39 d)
Bata f o r Figure 1$
Volume P e r ce n t
A ir

A l(^aa)
1 Megohm

1 .2 6

0.U2

2<>37

0 .5 7

5 .3 2

A I ( /ia )
0 .1 Megohm
U.5
7 .0

A J0 .1 Meg.
^ ^1 Meg.
10.7
12.2

1 0 .5

1 1 .2

1 .9

1 8 .5

9 .8

2 1 .1

29

9 .5

U0.9

3 .1
£ .2

8 .7

8 0 .2

7 .U

U5-5
55*0

1 0 0 .0

9*5

59 oG

7*U
6 .2