ABSTRACT

STATES IN 1168b FROM 116Te DECAY

AND 116Sn(p,nY)ll6Sb

by
Clare Ben Morgan

The 116Te beta decay and the 116Sn(p,ny)ll6Sb reaction with

proton beam energies between 5.95 and 11.75 MeV have been used
with Ge(Li) spectrometers to study properties of Y rays from

states of 116Sb below 1.48 MeV of excitation. The beta decay of

116Te is observed to directly feed four excited levels in 1168b.
The de-excitation of these levels produce 21 Y rays allowing the
placement of four additional levels. These eight states and 25
others were observed in the (p,ny) experiments. Using the
predictions of the statistical compound nuclear model, spin and
some parity assignments have been made based upon in—beam gamma—ray
angular distributions and excitation functions in conjuction with
the beta decay. These states and spin-parity are 0.0 (3+), 93.7
(1*), 103.0 (2*), 410.9 (4+), 455.2 (3), 466.0 (3), 503.1 (5),
517.9 (2*), 550.9 (2), 574.4 (2+), 612.5 (4), 654.1 (3), 731.6 (1+)
815.1 (3), 820.6 (5), 841.1 (6), 881.5 (3), 917.7 (1*), 948.0 (4),

1127.2 (2), 1158.3 (1+), 1222.9 (2) keV.

Branching ratios for 42 Y rays are presented along with all

Ineasurements of the multipole mixing ratio. Pulsed beam experiments

have been performed to measure the half-lives of the excited states.

The lifetime of the 455.2 keV state is discussed. The shell model

structure of low lying states is also discussed.

STATES IN 1168b FROM 116Te DECAY

AND ll6Sn(p,nY)ll6Sb

By

Clare Ben Morgan

A THESIS

Submitted to
Michigan State University
in paritial fulfullment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY

Department of Physics

1975

ACKNOWLEDGMENTS

I wish to thank Dr. W.H. Kelly for his encouragement and
interest during the experimental work and for his patience and
guidance during the preparation of this thesis.

I also wish to extend special thanks to Drs. L.E. Samuelson
and R.A. Warner for their invaluable assistance and encouragement
during the data acquision and analysis of this work. Many of
their ideas led to solutions to apparently insurmountable problems.

Dr. H.G. Blosser, Dr. P. Miller and Mr. Hilbert have assisted
with the operation of the Michigan State University sector-focused
cyclotron.

I wish to thank also Dr. W.C. McHarris and Mr. R. Au for their
contributions to many of my various projects.

Dr. E.M. Bernstein, Dr. R. Shamu and the staff at the Western
Michigan University tandem Van de Craaff Laboratory were extremely
generous with their time and facilities.

Dr. T.L. Khoo, Dr. F.M. Bernthal, Mr. w. Chaffee, Ms. C. Dors,
and Mr. B.D. Jeltema aided in data collection and interpretation.

Mrs. Peri—Anne Warstler aided greatly by typing the final
version of this manuscript.

Much of the financial assistance for this research has been
provided by the National Science Foundataion, The U.S. Atomic

Energy Commission, and Michigan State University.

ii

TABLE OF CONTENTS

ACKNOWLEDGMENTS

LIST OF TABLES. . . .

LIST OF FIGURES

I.

II.

III.

IV.

VI.

VII.

INTRODUCTION AND PREVIOUS WORK.

THEORETICAL CONSIDERATIONS.

A. Statistical Compound Nucleus Theory.

B. Shell Model Description.
116.

THE BETA DECAY OF 1e
A. Source Preparation .

B. Singles.

C. Gamma-Gamma Coincidence.

D. Level Scheme and Spin and Parity Assignments

The 116Sn(p,nY)1168b REACTION .

A. Gamma-ray Thresholds and Excitation Functions.

B. In-beam Gamma-Gamma Coincidence Measurements

C. Lifetime Measurements.

D. Gamma-ray Angular Distributions.

116
The ll8Sn(p,3nY) Sb REACTION.

A. Singles.

B. Gamma—Gamma Coincidence.
EVENT RECOVERY. . . . . . . . .
DISCUSSION OF INDIVIDUAL LEVELS

A. Ground State Jr = 3+ .

iii

Page
ii

vi

viii

ll

ll

l7

18

26

42

45

54

54

56

58

62

63

T.

VIII. SUMMARY AND CONCLUSIONS .

REFERENCES.
APPENDICES.

£5.

E = 93.7 keV J"

E = 103.
x

E = 410.
x

E = 455.
x

E = 466.
x

E = 503.
x

E = 517.
x

E = 550.
x

E = 574.
x

E = 612.
x

E = 654.
x

E = 731.
x

E = 815.
x

E = 820.
x

E = 841.
x

E = 881.
x

E = 917.
x

E = 948.
x

0

keV

keV

keV

keV

keV

keV

keV

keV

keV

keV

keV

keV

keV

keV

keV

keV

keV

Higher Excited States.

Integral coincidence and

Beta Decay of

16Te.

iv

gated spectra from the

Page
63
64
64
68
70
70
73
73
76
76
80
80
80
83
83
83
83
87
87
92
94

96

96

Page

Integral Coincidence and Gated Spectra from
the in-beam 116Sn(p,nY-Y)ll6Sb Reaction at
beam energies of 7.3 and 11.75 MeV and the
118

Sn(p,3nY-Y)1168b reaction at 30 MeV . . . . . . . 101

. 116

Angular Distributions of the Various Sb Y rays
Obtained from the 116Sn(p,nY)ll6Sb Reaction with

Ep = 5.95, 6.25, 6.65, and 7.32 MeV. . . . . . . . . 124

Table

III-l.

III-2.

IV-1.

IV-2.

IV-3.

IV-4.

IV-4a.

IV-5.

IV-6.

IV-7.

IV-8.

Iv-g 0

LIST OF TABLES

Results of two parameter Y-Y coincidence
116

experiment from Te beta decay . . . . .
Energies and intensities of 1168b Y's from 116Te
beta decay . . .

Internal conversion coefficients used in the
excitation function calculations . . . . . . . . . .
Form of the optical-model potential and parameters
used in the calculations of transmission coefficients
Ge(Li) detectors used in in-beam Y-Y measurements.
Gamma-ray energies from 1168b. . . . . . . . . .
Gamma-ray calibration energies used to determine

116

energies in Sb. . . . . . . . . . . . .

Results of two parameter Y-Y coincidence with

E = 6.54 MeV.

P

Results of two parameter Y-Y coincidence with

E = 7.28 MeV. . . . . . . . . . . .

P

Results of three parameter Y-Y coincidence with

E = 7.99 MeV. . . . . . . . . . . . . . . . .

P
Results of three parameter Y-Y coincidence with

E = 8.4 MeV O O O O O O O O O O O O O O O O O O

P

Results of three parameter Y-Y coincidence with

Ep = 11.75 MeV . . . . . . . . . . . . . . . . . .

vi

Page

13

14

21

24

28

32

33

34

35

37

38

39

Table

IV-lO.

IV-ll.

Results of angular distribution experiments at

5.95 and 6.25 MeV. .

Results of angular distribution measurements with

E = 6.65 MeV. . . .
P
Results of the angular distribution at E = 7.32 MeV

Results of three parameter Y—Y coincidence for the

118Sn(p,3nY) ll68b reaction. . . . . . .

vii

Page

49

50

51

57

III-3.
IV—1.
IV-2.

IV-3.

IV-4.

IV-5.

IV-6.

IV-7.

VI-l.

VI-2.

VII-l.

VII-2.

VII-3.

VII-4.

LIST OF FIGURES

Notation used by MANDY . . .

1168b. . . . . . . . . . .

Shell Model orbitals in
Gamma—ray spectrum from 116Te decay.

Detector arrangement for Y—Y coincidence .

1165b levels from 116Te E decay. .

Gamma—ray spectra as a function of beam energy
Arrangement for in-beam Y-Y coincidence. . . . . .
Integral and representative gated spectra form the
11.75 MeV coincidence experiment . . . . . .

Level scheme for 116Sb . . .

Comparison of a prompt Y ray to a delayed.

Time vs Y-ray energy for lifetime measurements .
Arrangement used for Y-ray angular distributions .
Comparison of singles from (p,nY) and (p,3nY)
reactions. . . . . . . . . . . . . . . . . . . . .
Tape reading routine in EVENT RECOVERY . . . .
Sorting routine in EVENT RECOVERY.

Excitation functions for 103.0, 410.9, 455.2, and

466.0 keV levels . . . . . . . . . .

Chi square and delta ellipse plots for the 93.7 and

103.0 keV gamma rays . . . . . . . . . . . . . .

Chi square and delta ellipse plots for the 307.8 and

410.9 keV gamma rays . . . . . . . . . . . . . . .

Chi square and delta ellipse plots for the 352.2 and

455.2 keV gamma rays . . . . . . . . . . . . . . .

viii

Page

10
12
16
20

27

31

41

43

44

46

55

60

61

65

66

67

69

1"

Va

9y»

._I

Figure Page
VII-5. Chi square and delta ellipse plots for the 363.0 and

92.2 keV gamma rays. . . . . . . . . . . . . . . . . 71
VII-6. Excitation functions for the 503.1, 517.9, 550.9,

and 574.4 keV levels . . . . . . . . . . . . . . . . 72
VII-7. Chi square and delta ellipse plots for the 424.2 and

517.9 keV gamma rays . . . . . . . . . . . . . . . . 74
VII-8. Chi square and delta ellipse plots for the 550.9 and

457.2 keV gamma rays . . . . . . . . . . . . . . . . 75
VII—9. Chi square and delta ellipse plots for the 480.6 and

108.5 keV gamma rays . . . . . . . . . . . . . . . . 77
VII-10. Chi square and delta ellipse plots for the 574.5 and

157.4 keV gamma rays . . . . . . . . . . . . . . . . 78
VII-11. Excitation functions for the 612.5, 654.1, 731.6,

and 815.1 keV levels . . . . . . . . . . . . . . . . 79
VII-12. Chi square and delta ellipse plots for the 628.7 and

637.9 keV gamma rays . . . . . . . . . . . . . . . . 81
VII—13. Chi square and delta ellipse plots for the 404.2 and

712.1 keV gamma rays . . . . . . . . . . . . . . . . 82
VII-14. Excitation functions for the 820.6, 841.1, 881.5,

and 917.7 keV levels . . . . . . . . . . . . . . . . 84
VII—15. Chi square and delta ellipse plots for the 208.1 and

778.5 keV gamma rays . . . . . . . . . . . . . . . . 85
VII-16. Chi square and delta ellipse plots for the 366.8 and

917.7 keV gamma rays . . . . . . . . . . . . . . . . 86

ix

Figure

VII-17.

VII—18.

VII-19.

B-l.

B-2.

B-3.

Page
Chi square and delta ellipse plots for the 294.1 and
395.6 keV gamma rays . . . . . . . . . . . . . . . . 88
Excitation functions for the 1045.1, 1127.6, 1158.3,
and 1222.9 keV levels. . . . . . . . . . . . . . . . 89
Chi square and delta ellipse plots for the 1055.3
and 705.0 keV gamma rays . . . . . . . . . . . . . . 91
Integral coincidence and gated spectra from the beta
decay of 116Te. Background subtraction using the
adjacent continuum has been included . . . . . . . . 96
Integral coincidence and gated spectra from the
in—beam 116Sn(p,nY-Y)116Sb reaction at 7.3 MeV . . . 101
Integral coincidence and gated spectra from the
in—beam 116Sn(p,nY-Y)ll6Sb reaction at 11.75 MeV . . 110
Gated spectra from the in-beam 118Sn(p,3nY-Y)116Sb
reaction at 30.0 MeV . . . . . . . . . . . . . . . . 120
Gamma-ray angular distributions obtained with the
proton energy at 5.95 MeV. The solid line
represents the least squares fit to W(0) as explained
in the text. The fit is normalized to 1 at 900.
The data in the lower right is normalized to the
isotropic 93.7 keV gamma ray . . . . . . . . . . . . 124

Gamma—ray angular distributions from the 116Sn(p,nY)

116Sb reaction at 6.25 MeV. The data are normalized

to the isotropic 93.7 keV ray. . . . . . . . . . . 126

Figure

C-3.

Page
Gamma-ray angular distributions from the
116Sn(p,nY)116$b reaction at 6.65 MeV. The

data are normalized to the isotropic 93.7 keV

Y ray. . . . . . . . . . . . . . . . . . . . . . . . 130
Gamma-ray angular distributions from the

116Sn(p,nY)ll6Sb reaction at 7.32 MeV. The

data are normalized to the isotropic 93.7 keV

Y ray. . . . . . . . . . . . . . . . . . . . . . . . 137

xi

I. INTRODUCTION AND PREVIOUS WORK

Understanding of the residual n-p interaction (that part of the
mutual interaction which is not accounted for by the central poten-
tial) is essential for full understanding of the structure of nuclei.
Nuclear spectroscopy of odd-odd nuclei is a convenient method of
examining this interaction. States are available at much lower
energies in odd-odd nuclei than in even-even nuclei, making them
more readily available. Little is known of these nuclei other than
they are very tightly packed with levels presenting serious experi-
mental problems. It is felt that near a closed shell there may be
some simplifications, therefore a series of investigations has been
initiated near the Z = 50 closed shell where many stable targets are
available so that the systematics may become more evident.

Little previous work has been done on the odd—odd antimonies
below A = 122 with the (p,ny) reaction. Elliot e£_313 have studied

122

low lying states in Sbl and Chaffee et_al,2 have studied states

in 1188b below 1200 keV via the (p,ny) reaction. The beta decay of

116Te has been studied by B. G. Kiselev et al;3, 0- Rahmouni4, and

Fink st 3135.

—-.—-—

Fink established the half life of the 116Te ground state as

2.50:0.02 hours and the existence of a 93.9 keV y ray.

Rahmouni established the existence of two additional y rays
and made tentative identifications of several others. He placed
excited levels at 93.5, 196.5, and 723.5 keV, depopulated by y rays
of energies 93.5, 103. and 630. keV respectively. More recently the

+ — .
spins and parities of the 3 ground and the 8 isomer states in

116Sb were measured by atomic beam studies by C. Ekstrom e£_§l,6.

The 116Sn(p,nY)1168b reaction was chosen for this study because
the reaction should be well described by the statistical compound
nuclear theories of Hauser and Feshbach7 as used in the computer codes
of Sheldon and Van Patter8-ll. It is expected that at the energies
used in these experiments (Ep = 5.5 to 7.5 MeV) the dominant part of
the reaction should be compound nucleus as opposed to direct reaction.
All states for which the incoming energy and angular momentum are
sufficient should be excited in this type of reaction. The statis-
tical model as applied to the excitation function data and angular
distribution data is an excellent method of making many unambiguous
spin assignments as was done here. In addition, Y-ray multipole mixing
ratios, precise level energies, and Y-ray branching ratios were

obtained.

In addition to the (p,nY) work, the Y-ray spectrum accompanying
the 116Te electron capture decay was investigated. These experi-
ments corroborated and complemented the in-beam experiments and were
able to resolve several discrepancies encountered in the in-beam
studies. Several gamma rays that were not observed by the previous

investigators were found.

The (p,3nY) and (a,3nY) reactions were also briefly investigated

to study the 116Sb nucleus.

-«—

L)“

t.
.11

lb.)
11-

b“ ‘

II. THEORETICAL CONSIDERATIONS

A. Statistical Compound Nucleus Theory

The basic tool for data analysis was the program MANDY8 written
by E. Sheldon and R. M. Strang which uses the framework of statistical
compound nucleus (CN) theory for the evaluation of angular distribu-
tions. Samuelson and Morgan have since modified MANDY so that it
may be used with excitation function data in a more straight forward
way. The program assumes incoming and outgoing particles with spins
of Szl/Z.

The general expression of the differential cross section written

as a Legendre-Polynomial expansion of even order is

——- = Z A P (c050)
v=0,2,4...

in which the summation extends over angular momenta entering into the
over-all process and over the index 0. The Av coefficients can be
decomposed into a product of energy—dependent and of momentum-depend-
ent terms.
2
A0 = 1/4 X ngfljijrjo‘Il;31)B\)(j2j2‘]3.‘]1;52)T

The Bv's are transition parameters loading to or decaying from CN
States J21. Two additional momentum dependent terms also appear 1,
which is the rationalized wavelength of the incident particle and g
which is a statistical spin factor that takes account of the probabil-
ity that the incident particles of spin 5 have the right orientation
f0r'resonance capture,

g = (2J1+1)/(2(2J0+1)(251+1)) = l/4(2J1+l).

The energy dependent term T is the Hauser-Feshbach penetrability

teI‘mwhere

 

 

 

.
A\

.113:

 

T = T (E )T (E )/ z T (E)
21 1 22 2 RjE 2

This term takes account of the CN barrier penetrabilities for incident

particles of energy E1 and emergent particles of energy E2 in the

ccnter-of-mass system. The sum runs over all possible decay channels.

The spin orbit interaction is included by use of generalized trans-

(i)
2

mission coefficients T , where they are related to normal coefficients
by

T2 = ((8+1)T(+)+8T(’)) / (22+1)

The notation employed by MANDY is summarized in Pig. II-l.
Gamma ray angular distributions as a function of the mixing ratios,

8, of the gamma rays are computed using

99 _ , *. -6 *,
d9 — A0(1+A2I2(cos6)+A4P4(cose))

*
where Av = Av/AO' The series for gg-is limited to the first three

terms as higher order terms are expected to be negligible. The multi-
pole mixing ratio 0 is the intensity of the gamma transition of multi-

polarity L+l (L') divided by the intensity of the gamma transition
9:

2

*
and A4 as a function of 0 form an ellipse where 0 takes on all values

of multipolarity L. The locus of points for possible values of A

‘k

*
2 and A4

usually allows a determination of 8 with its usually narrow error

from -m to +w. Comparison with experimental values of A

limits.

The calculated cross sections are highly dependent on energy of
bombardment and angular momentum. For the range of energies (5.5 to
7.5 MeV) used in this investigation, the cross section peaks at R =
1 or 2 and falls off rapidly with increasing values nearly vanishing

for values greater than 5.

 

Notation used by MANDY
Figure II-l.

b. 1,
WI ,.
w \l_
‘ v
4 fr.
VA &.
{‘2'}
‘«.g
9}]. '

‘ w
“L .-

 

‘1‘“.

-.‘\“

"w . .

 

'u‘1 P

€j9r

1‘ ‘1

.‘l'L

r

l.‘
I

 

 

Therefore all total cross section calculations were limited to

0:856.

8. Shell Model Description

Given the structure of the states, shell—model fits can be made
to derive matrix elements of the residual interaction. Full knowledge
of the residual interaction may help to lead to a more complete under-
standing of nuclear forces.

Antimony 116 with 2:51 and N=65, falls in the region between
the 50 and 82 closed shells for both protons and neutrons. For low
excitations (below approximately 1 MeV) the states should consist of
the various couplings of the single neutron and proton orbitals plus
various collective states. If we look at the neighboring even neutron

Antimonies (odd proton) we find the ground states are dS/7 with the

order of the other orbitals being 97/2’31/2’d3/2 w1th eXC1tation

energies of 724, 771, 1072 keV respectively in 1158b and 527, 720,

117 27,28

924 keV, respectively, in Sb The lies at a higher

1111/2
. 117 115
energy and has not been observed. The odd neutron 1n Te and Sn

116 28,29

give an idea of what to expect in Sb. The ground state in

both cases is 31/2, followed by d

h11/2 (380 and 726 keV respectively), and the 97/1 lies at a higher

3/2 (330 and 497 keV respectively),

unknown energy.

The ground state configuration is expected to be (ads/2,031/2).
Nordheim coupling rules, as modified by Brennan and BernsteinBO,
Predict that the spin of the ground state is

J = [J1+J = 5/2 + 1/2 = 3

2 I

 

 

 

} S1/2’d3/2’h11/2

 

 

 

} S1/2’d3/2’h11/2

 

 

g7/2 as
4i —~+eeeeee—— d
x d5/2 33mm 1536 g5/2
P 7/2
rotons
Neutrons
116

Shell Model Orbitals in Sb.

Figure II-Z.

This is in agreement with the recent atomic beam studies of C.

6 . . .
Ekstrom 91.31: Since the g7/2 state lies at = 600 keV in the
adjacent odd antimonies, we anticipate that up the configuration of

low lying excited levels probably include the proton d up to about

5/2
600 keV, with the various neutron states. The first excited 2+
state (see chapter 7 for discussion of spin assignments) is believed
to be the spin 2 coupling of the ground state configuration.

The next lowest neutron orbital is the d3/2’ which coupled to
the dS/Z proton orbital will produce states with JTr = 1 ,2 ,3 ,4
The J = 1 state might be the 93.7 keV state and the 4+ probably is
the 410.9 keV state. It is not possible to uniquely pick out the
2+ of 3+ states with this configuration as there exist too many
possibilities. The same is true of the hll/thich yields states
of 3- to 8_.

III. THE BETA DECAY OF 116Te

A. Source Preparation

Enriched 1168n was obtained from the Oak Ridge National Labora-
tory Isotope Division in the form of a powdered oxide. This was
placed within a rabbit12 (pneumatic target transport system) for
bombardment by the MSU Cyclotron with 71 MeV 3He. Since the Q-value
of the (3He,3n) and (3He,4n) reactions are -15.66 and -26.80 MeV
respectively, the cyclotron beam was degraded to 32 MeV with an
62 mil Al absorber. The 32 MeV was chosen on the basis of calcula-
tions with the computer code CS8N13, which predicted that the cross-
section for the (She,3n) reaction would peak at that energy. After
bombardment for periods of 30 to 60 minutes, the sources were allowed
to sit for approximately 30 minutes to allow undesired shorter lived
contaminant activities to decay. Then the activities were placed

within fresh aluminum foil enveIOpes for counting.

B. Singles

The samples were counted with an 18% efficient (the full energy
detection efficiency for the 1332 keV gamma of 60Co relative to that
of a 3 in x 3 in NaI(Tl) scintillator detector with a source to de-
tector distance of 25 cm) Ge(Li) detector that has a resolution of 2.0
keV FWHM and a peak to Compton background ratio of 45:1 for the 1332
keV gamma of 60Co. The singles gamma-ray spectra data were taken at
time intervals of 2.0 hours over a period of 10.0 hours. Those Y
rays with the correct lifetime of 2.5 hours were assumed to be

9

3000.0

O+®D

@lhlbn-

10

Door

.zmomn we

HIHHH musawm

Eoum Esuuomam zmulmEEmo

QHH

mmeDZ JMZZ<IO

 

 

Doom

[£16 ’
6289 '\.

[889 -’

 

 

Jaslnd _

moomc 0+on ow

w:

oooN

6'099 x

 

 

oooH

 

 

 

('86 -

 

 

 

‘IEINNVHZJ 83d SINIIOCJ

agLa‘."

3 «'
~tht
(‘9‘

'0 t

1.‘ 7».

Nil
~0141

5

4%.
jun

a:

’Eia g

11

candidates for placement in the decay of 116Te. In all sixteen Y

rays were found with the proper lifetime.

C. Gamma-Gamma Coincidence

The detectors used were the 18% Ge(Li) detector, previously
described, and an 8% Ge(Li) with 1.95 keV FWHM at 1332 keV and a peak
to Compton ratio of 33:1. The detectors were placed with a half inch
of lead between them to reduce Compton scattering from one detector
to the other. The source was placed at the end of the sheet of lead
(which lacked about a quarter of an inch of going to the edge of the
detectors) as is shown in Figure III—2. A singles counting rate of
about 2 X 104 cps was maintained in the 18% detector which gave a
coincidence rate of approximately 300 Cps. About 7 x 106 events were
stored on magnetic tape using the MSU on-line PDP-9 computer. The
data were recovered using weighted background subtraction with the
MSU Xerox SIGMA-7 computer. The results of this measurement are

found in Table 111—1.

D. Level Scheme and Spin and Parity Assignments

The level scheme constructed (Figure III-3) consists of eight
excited states, four of which are fed directly by electron capture
decay. These four states are the 1158.3, 917.7, 731.6, and 93.7 keV
States which have beta transitions with log ft's of 5.4, 6.3, 5.5,
land 4.7 respectively. Since these log ft's are low enough that the
beta decay is probably allowed, spin and parity assignments of either

1+ or 0+ can be made to these four levels. The log ft of the beta

12

Pb Compton suppressor

\

 

 

18% Detector 8% Detector

Ge(Li) Ge(Li)

 

 

 

 

 

L_3. 1»

 

 

116

Te source

Detector arrangement for Y-Y coincidence.

Figure III-2

13

Table 111-1. Results of two parameter Y—Y coincidence

experiments from 116Te beta decay.

 

 

 

Gated Y ray Coincident Y rays
(keV) (keV)
103.0 628.7, 1055.3
180.9 550.9
363.0 103.0, 108.5
366.8 457.2, 550.9
447.8 180.9
457.2 180.9, 366.8
480.6 93.7, 157.2
550.9 180.9, 366.8
574.4 157.2
628.7 103.0

1055.3 103.0

 

 

.VFJ //
1‘ _‘:. gt:
‘33,

”The

32%.

int

14

Table III-2. Gamma rays per 1000 decays of 116Te

 

 

 

Gamma ray (keV) Intensity (Y's/1000 decays)
93.7 958.21
103.0 29.46
108.5 .47
157.2 4.088
180.9 2.12
363.0 .59
366.8 1.31
447.8 .52
457.2 1.01
466.0 b
471.4 .42
480.6 3.7
550.9 2.90
574.5 .36
583.8 .87
628.7 30.29
637.9 7.14
824.0 1.08
917 7 1.38
1055.3 6.46C
1064.6 2.32C

\_

 

 

aThe intensity for the 157.2 keV Y ray was computed from the sum of the
'Y ray depopulating the 574.4 keV level.

1118 466.0 keV Y ray was not observed in the beta decay but is known to

Eiccount for 11% of the deexcitation of the 466.0 keV level.

C
111856 intensities were computed using the branching ratios obtained from

iJi—beam experiments.

falls
5“»
1v

9
b

p

1..

15

transition to the 917.7 keV level may indicate a first forbidden
transition, but this is considered unlikely as no such shell model
configurations should exist at this low an excitation. Gamma-ray
angular distribution data (described in Chapter IV) eliminates the

0+ possibility for all but the 93.7 keV level (which is isotropic
due to its long lifetime) as they are anisotropic. Electron internal
conversion work by Pink £3.2135 show that the 93.7 keV Y ray is an E2
transition to the 3+ ground state. Therefore, all four levels fed

by beta decay are assigned a spin and parity of 1+. The 103.0 keV
level is assigned a spin and parity of 2+, as described in Chapter
VII.

The spin 2 states are not expected to have any observed feeding
by beta decay of 116Te as this would require a second forbidden transi-
tion. The spins of the spin 2 and the excited spin 3 levels were
based upon in-beam gamma-ray angular distribution and excitation func—
tion data (described in Chapter VII).

An additional gamma ray of 466.0 keV (shown depopulating the
466.0 keV level) is known to exist from the in-beam studies, but was
not seen in the beta decay of 116Te. This is not surprising in view
of the fact that this gamma ray is very weak. Since the 157.2 keV
Y ray is obscured by the large 158 keV decay peak from 117Sb, its
intensity was computed from the depOpulation of the 574.4 keV level,
as there should be no direct beta feeding to this level. The three
Y rays de-exciting the 1158.3 keV level were observed in the coincidence
data, but only the 583.8 keV Y ray was observed in the singles (due
to a low amplifier gain setting). The intensities were inferred

Using the branching ratios obtained from the in-beam measurements

discussed in Chapter IV.

16

116Sb levels from 116Te 8 decay.

 

/ II6

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5 2 Te 84
Q. . 1.5
i356
0398;}
’38 .
69%;} ”5' 7. L06 FT
1’ “a 1158.3 ./ 0.88 5.42
9 e \\
a)?
«‘96:»
‘1"? . _/
1‘ 9" -912] 0.38 8.3
\
«\q, ®
1M§$-
4.39892? "
1’ Q’ * * 731.6 / 9.38 5.5
\fg’e\‘.‘\q®gy\;b
2 ““6339 4 579.9
2 {€52 550.9
6 6
6"?
_3 “69° 988.0 __
Q) \
2* (1*
05%?
@1‘
2’ '9 6' 103.0
__1__, 9_::__§;2Jfl4§£Q//’ 9%29 $7
_3° 0.0
1188b 7': / 1000 decoys
51 85

Figure III—3.

A1
accurat

11619,,

IV. THE 116Sn(p,nY)1168b REACTION

Although the Q-value for the 116Sn(p,nY)1165b reaction is not
accurately known, it is near the value (-5.37 MeV) calculated from
the 1972 mass compilation14

Four different types of gamma-ray experiments were performed
using the 116Sn(p,nY)116Sb reaction: excitation function measure-
ments, gamma-gamma coincidences, lifetime measurements and angular
distributions.

In the first type of experiment, excitation function data were
taken from below threshold up to approximately 1.78 MeV of excita-
tion. The excitation functions provided threshold information which
greatly aided in the placement of the gamma rays within the excited
level scheme. Also these provided information on relative cross
sections as a function of proton energy. The cross sections can be
related to the spins of the levels producing a method of making these
assignments which complements the angular distribution method. Gamma-
ray branching ratios were derived from the individual spectra.

In the second type of experiment, gamma-gamma coincidences were
measured with a Ge(Li)-Ge(Li) spectrometer for excitation energies
of 1.0, 2.5, 2.8, and 6.2 MeV. Except for the case of ground state
transitions (or to the delayed 93.7 keV state) involving no coinci-
dences, this method is an excellent way to identify those gamma rays
Which belong to the de-excitation of 116Sb and is a great asset in

placing them within the level scheme.

The third type of experiment was a lifetime measurement using

a beam sweeping system. These measurements indicated that there are

17

18

two delayed states,tflu393.7 keV state with a lifetime of greater than
approximately 0.2 microseconds (not measured) and the 455.2 keV state
with a lifetime of 1.85 0.06 nanoseconds. This method is a very good
way to identify those contaminant gamma rays which are from beta decay
as they will appear with very long lifetimes.

The fourth experiment is angular distributions of the various
116Sb gamma rays for excitation energies of 400, 750, 1150, and
1830 keV. Where possible, the beam energies were chosen such that
the particular states in question were not fed from above by gamma-
ray transitions. The gamma-ray angular distributions provided

information on Spins, gamma-ray multipole mixing ratios, and gamma-

ray branching ratios.

A. Gamma—Ray Thresholds and Excitation Functions

Gamma-ray excitation data were taken from approximately 75 keV
to 1.0 MeV of excitation in 50 keV steps, and from there to 1.5 meV
in 100 keV steps. The proton beam energies ranged from 5.64 to 7.15
MeV. These data were taken with the Western Michigan University
Tandem Van de Graaff. The target was 3 116Sn foil of about 95%
purity and a thickness of approximately 1 mg/cm2 which contributed
33 keV to the energy spread of the proton beam for a beam energy of
5.5 MeV and 27 keV for a beam energy of 7.5 MeV. The gamma rays from

116Sn(p,nY)ll6Sb reaction were detected with a 10.4% efficient

the
Ge(Li) detector (with a peak to Compton of 35:1 and a resolution of
2.0 keV FWHM) at approximately 55 degress (which is close to a zero

of P2(c050)) from the beam direction at a distance of 5.5 cm. This

l9

acts to minimize angular distribution effects and allows one to more
directly use intensities to calculate branching ratios for the various
gamma rays. The charge was collected and integrated in an elec-
trically shielded piece of lead—lined aluminum beam pipe. The
integrated current was used to trigger a tailpulse generator which
was fed into detectors preamplifier giving dead-time and amplifier
pile—up corrections. The pulser peak was placed so as not to inter-
fere with Y-ray peaks and was used as a run to run normalization.

The Y-ray spectra were stored in the WMU on-line PDP—lS computer as
4096 channel spectra with about 0.3 keV per channel. Run times were
typically 1 hour with typical counting rates of 4000 cps to 8000 cps.

Gamma-ray spectra that show the growth of the 116Sb Y rays
with increasing proton beam energy are shown in Figure IV-l. The
threshold information and gamma-ray intensities obtained from these
data were crucial to the placement of several levels and their assoc-
iated gamma rays.

For neutron cross sections the neutron population of each state
was determined by subtacting the total intensities of all electro-
magnetic transitions to a particular state from the sum of the in-
tensities of all electromagnetic transitions de-exciting that state.
Internal conversion coefficients were used as in Table IV-lls. Where
the multipolarity of a transition was unknown, for this calculation
it was assumed to be Ml. Other conversion coefficient corrections
were determined to be less than 1% and were ignored. The gamma
intensities were determined by the peak fitting program SAMPO21

and the detectors' relative efficiency curves. All intensities

were normalized to the pulser peak. These relative cross sections

 

 

1 .

=22. w W W W W W .1

_

” 9'00. . I u

i 030. _

_ .4 s s o 1
s 5

. .6 o 9 a n u u w a. m u m. a m m. m m a u _

_ a. 7 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 5 .

:1 ..

 

 

C
a
0.0 —n o h
'09! “(:5 -c".".
9* :2: "sis
I
W 6.00
II

 

 

 

 

 

 

 

 

 

II

F.
0 80.0.
C' '9 .
F “O
' 0 Q0 \1 ,
l‘ 1
.A
.A
—L .1
L _L_.

ill-II. .. I . I.

 

 

 

0.3.
. Ema

L

ails
L_______.

g“ ——_—Iw§§‘62.-3‘

3 «:5. mg.“ :39 3

' I
1

3.2. 3.90 Eoom

Energy (keV)

Gamma-ray spectra as a function of beam energy.

Figure IV-l.

21

Table IV-l. Internal conversion coefficientsa used in

the excitation function calculations.

 

 

 

Gamma ray GK aL total
(keV) (K+1.33*L)
92.2 0.6518 0.0821 0.7609
93.7 1.6176 0.5088 2.2943
103.0 0.5030 0.0613 0.5845
108.5 0.4015 0.0516 0.4702
157.4 0.1429 0.0179 0.1666
180.9 0.0954 0.0137 0.1136
208.1 0.0730 0.0091 0.0851
307.7 0.0313 0.0042 0.0369

 

a .
These values were obtained from Reference 15.

U “—4
__1

11.1I

II
A
n)

H
-4.

 

22

are shown in Chapter VII where they are used as an aid to the spin
assignments.

The data were analyzed using a modified version of the computer
code MANDY10 containing ABACUS II16 as a subroutine. The simplified
program input consists of masses of target and resultant nuclei, 0-
value, beam energy, and for each level in the target (for inelastic
scattering) and the resultant nucleus, the energy, spin and parity
were included. The program calculates all transmission coefficients
for all 2 values having coefficients greater than 10.6 for all levels
energetically possible. MANDY then produces cross sections for
0+:3fl;6+ and O—égné6- for each level, using all other levels as extra
exit channels. Spins higher than 6 have cross sections that are
vanishingly small at the proton energies used here and were deemed
not necessary for the present data. Since the cross sections are
dependent upon the extra exit channels (which are also the results of
the calculation) the process must be an iterative one, until the
results match the input. The placement of Y rays within the level
scheme and all of the spin assignments must be correct to obtain
Completely correct results from MANDY for the excitation fuction
data.

MANDY uses a general statistical model approach8 to calculate

1168b as a function

the total cross sections for each level within
0f beam energy. The program assumes that a compound nucleus is formed
With no fluctuations in level density or of the density of the states
With specific spins and parities. The probability of forming the

COmpound nucleus is that obtained from the transmission coefficients

PTOduced by the program ABACUS 1116 using optical model parameters

23

from Perey and Buck17 (Table IV-Z).

The general expression for the differential cross section is

O-IO‘
.‘OQ

= 2 Av Pv(c050)
v=0,2,4...

where for the excitation functions we are interested only in the

A0 term, which gives the total cross section. The expression for

 

 

AO obtained from Chapter II and simplified is
2 (2J +1)Tx2
A = A gt = l
0 4 4(2JO+1)(281+1)

where g is the statistical spin factor and X'is the rationalized

wavelength for the incident particle. This gives the relationship

for o the total interaction cross section used by MANDYIO.

o = Z4nA = WAX T(2.Jl+1)(2JO+1)-1(281+1).1

The Jl's are the nuclear spins of the compound nucleus (CN)

levels, 8 is the spin of the incoming proton and J0 is the targets

1
ground state nuclear spin (0 for our case). The penetrability term
T is a measure of the relative probability of barrier penetration

by particles and is a function of transmission coefficients T£j(E).

T = T£j(E1) T£j(E2) /2 T£J(E)

24

.NH .wmm Eowm mum om> c0u0pd ecu cam mwoumsmwmd couusm: mshn

.NN .mmm Eouw mum .om> unmoxm .mumumemuma oeuoua exam

 

 

 

 

 

 

o . o
u u .H H
m\a<. .a M\H< a
m m
m 6\Am-uvm + a mm.o.a 1W1. mmm. + .m\A.m1uV + H mm.a3 H + 6\Amuuv + a o> 1 Auvo> n >
H e 68 e .65 e a
> N

m.e 58.0 me.o mm.a mN.H OH mam.o I o.wq acouusmz
m.a Ne.o me.o mN.H mN.H Ha M\HI<N + mam.oux.ee accuowm
A>6zv Abe Ame Ame Ame A>6zv A>6zv comaoaz
Om> .m w my» OM Q3 O>

 

 

.>oz cw comaosc mnu mo xwuwcm mmmEIMOIHoucmo ecu mw m wmuoEmwma one .flmu m\H<mm.H mswpmu
we mumnam vmwpmno AHEpoch: m ou map umnu mw .Auvo> .Hmwucmuoa escasoo was .mucmwoflwwmoo

cofimmfiEmcmuu mo mcofiumaaofimo ego a“ cam: mpmumEmpma cam Hmwucmuoa HavoEIHmoHuao may mo Epcm .~1>H magma

25

The sum extends over all open channels, including inelastic scattering,
by which the CN state can decay. The transmission coefficients
depend upon the particles' center of mass energy, and orbital and
total angular momenta 2 and j, respectively.

The sum in the total cross section expression is made over all
possible values of jl and jZ’ which are the total angular momenta
of the incoming protons and outgoing neutrons. Since this sum
involves the spins of the intermediate compound-nuclear states,
parity conservation and the angular momentum coupling rules require
a different sum over the penetrability term for each final excited-
state spin and parity. Since the target has J1T = 0+ and the outgoing
neutrons are mostly 2 = 0, the spin of the final state is determined
predominately by the angular momenta of the incident protons. At
these energies the incoming protons are mostly 2 = 2. Therefore
the cross sections are expected to be largest for J values of l and 2.

The proton transmission coefficients were calculated using the
local optical model parameters listed in Table IV-Z. The neutron
transmission coefficients were calculated using the local equivalent
Optical model parameters of Perey and Buck17. It was assumed that
the energy dependence would allow the use of the proton parameters
at proton energies as low as 5.5 MeV and the neutron parameters as
high as neutron energies of 2 MeV, i.e. within the energy range used
in these experiments .

All known inelastic proton channels (12) below 2.9 MeV were
used along with all known open neutron channels in each MANDY calcu-

lation.

To eliminate possible systematic errors introduced by Optical

30081

26

model parameters, the cross sections, both experimental and calculated,
were normalized to a level having a known JTT (in this case the 93.7

keV level). Internal consistency of the present experimental results
indicate that these possible errors are minimal. It is believed that

a high density of unobserved states above approximately 1 MeV of
excitation was responsible for the observed disagreement (the experi-
mental values were much lower than theory) for states in that energy
region. Comparisons of these cross-section ratios are made later in

Chapter VII.

B. In-Beam Gamma-Gamma Coincidence Measurements

Proton beams of 6.54, 7.28, 7.99, 8.4, and 11.75 MeV (lab)
were obtained from the MSU Cyclotron for the different in-beam
coincidence measurements. The target used was a 15 mg/cm2 116Sn
foil enriched to approximately 95%, and rolled from the metal powder
which was obtained from the IsotOpes Division of Oak Ridge National
Laboratory. The detectors used are briefly described in Table IV-3.

The detectors were positioned as shown in Figure IV-2. The
lead block between the detectors has a 1.3 cm diameter hole drilled
almost through it and serves as a shielded beam stop as well as an
attenuator for Compton photons scattered from one detector into the
other.

Two experiments consisted of a typical two parameter, fast-
slow coincidence arrangement with constant-fraction timing discrimina-

tion. The single-channel analyzer window set on the output from a

time-to-amplitude converter was slightly smaller than the approximately

 

11.1-7 __

Detector l I ,

 

 

 

I Detector 2

 

; .
, I .1
. 7n
I Ge(Li) I :_ J I Ge(Li)
‘ I_____.. -1_1 I
I .
I.
Pb BEAM STOP and
"COMPTON SUPPRESSOR"
L_.J l__11_4__4
0 1 2 3 4 5
SCALE (CM)

Arrangement for in-beam Y-Y coincidence.

Figure IV-2

28

Table lV-3. Ge(Li) detectors used in in-beam Y-Y

 

 

 

measurements.

Ep(MeV) Detector l Detector 2
6.54 4.5% 7.0%
7.28 4.5% 7.0%
7.99 4.5% 7.8%
8.30 4.5% 7.8%

11.75 10.0% 7.0%

 

The detectors are listed by their efficiency for the full energy de-
tection for the 1332 keV gamma of 60CO relative to that of a 3 in

X 3 in NaI(Tl) scintillator detector with a source to detector distance
()f 25 cm. The energy resolution for these detectors ranges from 1.9

l<eV to 2.2 keV FWHM for the 1332 keV gamma of 60CO.

29

70 nanoseconds between the beam bursts.

The last three experiments were performed as three parameter
gamma-gamma-time experiments. The TAC output was preserved, along
with the energy information, for later analysis.

Coincident events were stored on magnetic tape as pairs or
triplets of channel numbers, and sorted Off-line using weighted back-
ground subtraction.

The short half life of the ground state (15 min) resulted in
a large radioactive build up of beta decay within the target. At
equilibrium nearly half of the detected activity could be attributed
to the beta decay.

The spectra produced by the 6.54 MeV protons contained about
5 X 106 events taken during a 2 day period. The 7.28 MeV spectra
contained close to 8 X 106 events and the 11.75 MeV spectra more than

55 X 106 in the same time duration. Typical singles counting rates

ranged from 1.5 X 104 to 2.0 x 104 counts per second in the detectors
with up to 700 cps of coincidence events. The beam current required
was typically about 2 nanoamps.

Numerous programs were used to recover the data from the mag-
netic tapes. The first program (used for the Ep = 6.54 MeV data)
allowed 10 gates to be recovered simultaneously from tapes containing
Up to 1.8 X 106 events of 2 parameter data. Three parameter data
(approximately 3.5 X 106 events per tape) were initially recovered
with a similar program. Finally our most recent program (Chapter VI)
will recover up to 120 gates of 2 or 3 parameter data, simultaneously.

EXecution time is only slightly longer than the original program thus

giving a savings of an order Of magnitude in computer time for cases

I)
1‘3“:

1“!
.A‘

u

IECI‘

\

n.\~

éOUE:
with

30

where large numbers of gates need to be recovered.

The integral spectra, along with some representative gated
spectra from the coincidence experiment with Ep = 11.75 MeV, are
shown in Figure IV-3. Fifty-nine Y rays were definitely identified
by fast coincidences to be from 1165b. The energies of the 116Sb
Y rays are listed in Table IV-4, and the coincidences observed between
these y rays are listed in Tables IV—S through IV—9. All the gated
spectra can be found in the Appendix.

The positions of the levels within the level scheme shown in
Figure IV—4 are consistent with the coincidence and excitation func-
tion data. Dots denote Observed coincidence relationships between
Y-ray transitions entering and leaving a state. The spin assignments
(except that Of the ground state) are based upon the present work
and will be discussed in detail in Chapter VII.

All levels built upon the state with a measurable lifetime
(the 455.2 keV state) have no transitions to other levels indicating
that they may be negative parity states which Ml decay until they
reach the lowest possible negative parity state where they must
undergo an R-forbidden El transition.

Because Of high Compton background and the large number of
transitions present, it is possible that some ground state and isomeric
transitions have not been identified. Several difficulties were en-
COuntered during the construction of the level scheme from problems
With unresolvable doublets in the spectra. Two Of these are the
48C).6 keV Y's and the 550.9 keV Y's which were determined to be doublets
af'ter great effort. Difficulties were also encountered with the large

117S 116Sb Y

158.5 keV Y ray from the beta decay of b. Two of the

31

 

 

 

 

 

 

 

 

 

 

L

 

 

 

 

us 'E6Zl
US°86ZI
I
4 II US '286 ‘
) us °zc6
‘I
I
I)
I ZIL (
I
1'829
6'05;
9.0,? “119
Z'vzv
2'90? 6 019
0'898
T'8EE Z'ZSE
0°vzz
V'LSI
us 'SEI O'EOI
2‘26
L4___,- 1. - - - - - - - -
O O O O O m <7 (*1
Q in C no O O O O O O O
N Ln N O In C Ln 1—1 H r-4
°‘ \0 q N o <r m H

Integral and representative gated spectra from the 11.75 MeV coincidence experiment.

Figure 1V-3

Table IV-4. Gamma-ray energies3 from

32

116

Sb.

 

 

 

 

1 02.2 410.9 653.9
2 93.7 424.2 705.0
3 103.0 432.6 712.0
4 108.5 447.8 762.1
5 157.2 455.2 778.5
6 157.4 457.2 785.6
7 176.7 466.0 815.1b
8 180.9 470.6 824.0
9 208.1 471.4 867.5
10 224.0 480.6b 868.6
11 294.1 518.0 870.3
12 307.8 550.9b 874.7
13 338.1 574.5 894.4
14 352.2 583.8 907.7
15 363.0 590.1 917.7
16 366.8 596.1 948.4
17 380 612.5 1025.9
18 388.9 621.5 1055.3
19 395.6 628.7 1064.6
20 404.2 637.9 1129.2
8Errors are approximately 0.1 keV for energies less than 600 keV and

range from 0.2 to 0.5 for energies above 600 keV.

These Y rays have been determined to be doublets.

33

 

 

 

Table IV-4a. Gamma—ray calibration energies used to
determine energies in 116Sb.

EY(keV) Source Ref.
88.036:0.008 10906 23
122.061:0.010 57CO 23
136.47li0.010 57CO 23
165.853i0.007 1390a 23
279.189i0.006 203Hg 23
391.688:0.010 113$n 23
513.996i0.016 85Sr 24
661.638i0.019 13705 24
846.790i0.030 56CO 25
898.021:0.019 88y 24
931.800:0.050 1168n 26
1173.208i0.025 60CO 24
1238.300i0.020 56CO 25
1293.538i0.040 1165n 26
1332.49110.041 60CO 24
1771.41010.030 56C0 25
1836.130i0.040 88x 25
2015.360i0.030 56C0 25

 

 

34

Table IV-5. Results of two parameter Y-Y coincidence

with Ep = 6.54 MeV

 

 

 

Gated Y ray Coincidence Y rays
(keV) (keV)
103.0 108.5, 352.2, 363.0, 471.4, 550.9, 628.7
108.5 103.0, 363.0
157.2 8 157.4 103.0, 352.2, 480.6
352.2 103.0, 157.4
363.0 103.0, 108.5
480.6 157.2
550.9 103.0

628.7 103.0

 

 

35

Table IV-6. Results of two parameter Y-Y coincidence

with Ep = 7.28 MeV

 

 

 

Gated Y ray Coincidence Y rays
(keV) (keV)
92.2 103.0
103.0 92.2, 157.4, 208.1, 307.8, 352.2, 363.0,

471.4, 550.9, 628.7, 712.0, 778.5, 1055.3

108.5 103.0, 363.0

157.2 a 157.4 103.0, 208.1, 352.2, 455.2, 480.6, 388.9
208.1 103.0, 157.4, 352.2

294.1 550.9

307.8 103.0

352.2 103 0, 157.4, 208.1, 388.9, 590 1, 880.a

960. , 1025.9

363.0 103.0, 108.5, 621.5, 762.1, 870.3

366 8 103.0, 457.2, 550.9

395.6 103.0, 628.7, 638.9

404 2 307.7, 410.9

410 9 92.2, 404.2, 470.6

424.2 93 7, 480 6, 705.0, 815.1, 867.5, 907.7
447.8 103.0

455.2 8 457.2 366.8, 785.6, 874.7

4466.0 103.0, 307.7, 410.9, 629.3

470.6 a 471.4 103.0, 410.9

480.6 157.2, 424.2, 653.9, 762.1

 

 

36

 

 

 

Table IV-6. Continued
Gated Y ray Coincidence Y rays
(keV) (keV)

546.23 103.0, 550.9, 457.2

550.9 103.0, 180.9, 294.1, 366.8, 546.23, 829.a
874.7

612.5 550.9

628.7 103.0, 395.6, 363.0, 550.9, 653.9, 735.3

653.9 480.6

705.0 424.2, 518.0

712.0 103.0

762.1 103.0, 363.0, 480.6, 471.4, 574.5

815.1 424.2

870.3 363.0

874.7 457.2, 550.9

880.a 352.2

907.7 424.2, 518 0

1055.3 103.0

¥

. . . . ll
aThese gamma rays seem to be in c01nC1dence with 6

Sb Y rays but were

not placed within the present level scheme.

37

 

 

 

Table IV-7. Results of three parameter Y-Y coincidence
7.99 MeV

Gated Y ray Coincident Y rays

(keV) (keV)

103.0 157.4, 307.8, 352.2, 363.0, 471.4, 550.9,
628.7, 712.0

108.5 363.0

157.2 8 157.4 103.0, 208.1, 352.2, 455.2, 480.6

208.1 157.4, 352.2

307.8 103.0

352.2 103.0, 157.4, 208.1

363.0 103.0, 108.5

404.2 410.9

410.9 404.2

424.2 480 6, 705.0

455.2 8 457.2 157.4

470.6 410.9

480.6 157.2, 424.2

550.9 103.0, 366.8

628.7 103.0

705.0 424.2

4.3

DD

38

Table lV-8. Results of three parameter Y—Y coincidence

with Ep = 8.4 MeV

 

 

 

Gated Y ray Coincident Y rays
(keV) (keV)
103.0 157.4, 352.2, 363.0, 550.9, 628.7
157.4 103.0, 208.1, 352.2
208.1 103.0, 157.4, 352.2
307.8 103.0
352.2 103.0, 157.4, 208.1
363.0 103.0
410.9 92.2, 404.2
480.6 424.2

550.9 103.0

 

 

39

Table IV—9. Results of three parameter Y-Y coincidence

with Ep = 11.75 MeV

 

 

 

Gated Y ray Coincident Y rays
(keV) (keV)
92.2 307.8, 338.1, 410.9
103.0 92.2, 108.5, 157.4, 208.1, 294.1, 307.8,

352.2, 363.0, 471 4, 550.9, 570.73, 590.1,
628.7, 712.1, 778 5, 868.6, 1055.3

108.5 363.0

157.2 8 157.4 103.0, 208.1, 352.2, 380., 388.9, 432.6,

455.2, 480.6, 868.6

178.6 380.

208.1 103.0, 157.4, 352.2, 455.2, 388.9

224.0 103.0, 338.1, 410.9, 708.8

294.1 103.0, 550 9

307.8 92.2, 103.0

338.1 92.2, 103.0, 224.0, 307.8, 410.9, 682.3

341.33 735.7a

352.2 103.0, 157 4, 208.1, 380., 388.9, 590.1
868.6

363.0 103.0, 108.5, 621.5, 629.8

366.8 457.2, 550.9

388.9 103 0, 157.4, 208.1, 352.2

404.2 410.9

410.9 92.2, 224 0, 338.1, 404.2, 470.6

424.2 480.6, 705.0, 815.1, 890.8

 

Table IV-9. Continued

40

 

 

 

Gated Y ray Coincident Y rays
(keV) (keV)

432.6 103 0, 157.4, 352.2

447.8 103 0

455.2 157.4, 208.1

470.6 8 471.4 103.0, 410.9

480 6 157 2, 424.2, 518.0, 762 1

482.3 338.1

546.28 550.9

550.9 103.0, 294.1, 366.8, 570.73, 635.3

570.7a 103.0, 550.9

590.1 103.0, 352.2

621.5 363.0

628 7 103.0

705.0 424.2

712.0 103.0

778 5 103.0

868.6 103.0, 157.4, 352.2

894.4 103.0

R
\

aThese gamma rays seem to be in coincidence with 1168b Y rays but
were not placed within the present level scheme.

 

4|

 

Level scheme for 116Sb.

116
51

Figure lV—4

42

rays lie very close in energy (157.2 and 157.4 keV) to this huge
decay peak, causing problems with the resolution of these peaks.
The 157.4 keV peak can be resolved at higher energies where the
intensity becomes comparable to that of the 158.5 keV Y ray. However,
the 157.2 keV Y ray cannot be resolved as it is too weak and too close
to the 157.4 keV Y ray. It's existence has been indicated by the

116

coincidence data, both from the beta decay of Te and the in-beam

gamma-ray experiments.

C. Lifetime Measurements

A proton beam of 7.3 MeV (excitation Of 1.93 MeV) was obtained
from the MSU Cyclotron for the in-beam lifetime measurement. The
target used was the thick target described in the Y-Y section. The
detector used was a Low Energy Photon Spectrometer (LEPS) which has
very good timing characteristics in the few nanoseconds region.

The detector was positioned at 90° with respect to the beam
direction. Preamplifier pulses from the detector were used to start
a time-to-amplitude converter which was stopped by a pulse from the
CYClotron R.F. unit.

The data was collected by the MSU Sigma 7 computer as two
Parameter (energy vs time) events. Ten windows of equal width (4.052
ms) were set upon the time axis. The data were then sorted into ten
Single parameter spectra using these windows.

Analysis of the data was done using the time centroid shift of

116S

the delayed peak relative to that from a prompt peak. Two b

y rays (352.2 and 455.2 keV) were found to have measurable lifetimes

#\

10

10

10‘

10

10

10

10

10

43

Figure IV—5.

Comparison of a prompt Y ray to a delayed.

 

fTVUU‘

‘

r

f1 T'U'T

T

v Irvul

 

T r T1 ‘__

     
   
 

t = 1.85:.O6nsec

1
’2

352.2 keV

363.0 keV

\
/ \1

L m- J J 1

0 2 4 6
time (band #)

Laan

1

A I A All

I

L ‘4‘

JIALULI

_L__l

 

44

A>mxv zwumcm xmulmeamo

 

 

 

com com 005 com OON OOH
. _ . .;.:aé.:1111l1 11 _ :11 .4
1. .7.
.mucmamuammme mefiummaa new swumcm %mu1> m> mEHH _
.81: 35w; W
L.
fl
w\
r 88.484 n .0 5mm: H...\
mm >3 me a
baa .H
O .
nmoaa > Mommm \\
>Ox mmq -1 .
T 1.11. . 1/ 1
H H» ....... 11.811
dflH.,i%- II vamp umfioum
IIHIhWIAIIIHB I
r P p p -

 

 

Time (band #)

45

(only the 93.7 keV Y ray has a longer lifetime). The centroid shift
found (mean life) was 2.66i0.08 nsec which gives a halflife of 1.85i0.06
nsec.

The multipolarity, L = l, for the 352.2 keV transition, as
obtained from the angular distribution experiments described in
Chapter IV Section 0, indicates that the transition must be hindered
by a factor Of 3500 if it is El and by 100 if it is M1. Electric
and magnetic dipole transitions in odd A nuclei in this region are
known to be hindered by these amounts.
The neutron single particle for negative parity states must be
hll/Z’ assuming that negative parity states produced by protons lie
considerably higher in energy. Since the lowest lying states are

either (Nd ) or (Nd ) the resultant El transitions

5/2' “d3/2 5/2’Vs1/2
would involve changing the neutron from a J of 11/2 to 3/2 which would

be a fi-forbidden transition and therefore probably hindered.

D. Gamma-Ray Angular Distributions

Proton beam energies Of 5.95, 6.25, 6.65, and 7.32 MeV were
obtained from the MSU Cyclotron for in-beam measurements Of gamma-
ray angular distributions. The target used was the same target as
used in the excitation function measurements. The detector used
was an 8% efficient EDAX Ge(Li) detector.

The detector was positioned as shown in Figure IV-7, with angles
from approximately 15 degrees to 90 degrees available for use. The
beam was stopped in a small lead cup placed at zero degrees. Those

Y rays which were produced from the beam hitting the beam stOp had

46

“Ouomumv

sap-» Aaavmo Nw

neuowumn :Ououa umfiuumn .
/ mommuzm Hm acumsmmm pm

       

BOOCwB

'0 9v- '6 ' l

woman umwume *

 

 

 

deuamx .EEmNo.o

Arrangement used for Y-ray angular distributions.

Figure IV-7.

adefini
greater
easily.

Th1
compute
verters
from 15
many p0
to incr

forlh

ielvels ‘

47

a definitely unique angular distribution, which gave 5 to 8 times
greater intensity at small angles, allowing them to be disposed of
easily.

The data were stored in the MSU Cyclotron Laboratory's Sigma 7
computer using the Northern Scientific 50 MHz analog to digital con-
verters (ADC's). Data were collected in a random order of angles
from 15 to 90 degrees to minimize possible systematic errors. As
many points as possible were duplicated to check reproducibility and
to increase confidence in the data. Typically, data were accumulated
for 2 hours at each angle.

The first experiment at 5.95 MeV produced only the 93.7 and
103.0 keV Y rays. The normalization was produced by detecting the
elastic protons with a silicon detector at an angle of 45 degrees
(on the side Opposite the Ge(Li) detector). A single channel analyzer
window was set upon the elastic events. Every tenth pulse from the
elastic events was used to trigger a tailpulse generator which was
then fed into the detectors preamplifier making possible dead-time
and amplifier pile up correction. The pulser peak was placed so as
to not interfere with any Y ray peaks. The results of this first
run indicated that, to within very small errors, the 93.7 keV‘transi-
tion is isotropic. Although the pulser normalization was included
in later runs, it was found that much better consistencies were ob-
tained by using the intensity of the 93.7 keV Y ray as the normaliza-
tion.

Although the thickness Of the target and the density of states
above 400 keV Of excitation make it difficult to selectively populate

levels with an appreciable yield, it is possible to choose energies

of Nita
lying Ste
4.35 IIeI'I
from I113}
Framed
:EY’BIS .

Prcd‘dC ed

of IAII I Ch

the high‘
set of If
Peal

311mb.

using thl
91112018
321

id an

Tables I

psitn'e
between ‘
:xperimer

11:0 the

48

of excitation such that very little or no Y-ray feeding from higher
lying states is observed. The second angular distribution (E =

6.25 MeV) populated the levels up to 612.5 keV with very little feeding
from higher states to this last level. NO serious perturbations were
produced by the three possible weak Y rays which could feed lower
levels. The experiment with the third beam energy (Ep = 6.65 MeV)
produced angular distributions from an additional five levels, none

Of which could be gamma fed from above.

The final experiment was performed at an excitation higher than
the highest known state (1481 keV) in 116Sb producing an additional
set of levels not known to be gamma fed from above.

Peak intensities were derived from the peak fitting program

SAMPOIS, and fit to the equation

W(0) = AO(1+A2P2(c050)+A4P4(c050))

20

using the least squares fitting computer code GADFIT . The parameters
extracted from the fit are AO (the intensity integrated over all
solid angles), A3, and AZ. The A; and AZ'S measured are found in

Tables IV-10 through IV-12.
The angular distribution data were analyzed using the modified
MANDY8 program described in Section IV-A. For each Y ray, 180 values

0f the gamma ray multipole mixing ratio (0) for 0:03-2éd :J +2 for both

2 3

POSitive and negative parity were calculated. The differences Obtained

between the positive and negative parity values are smaller than the

‘k *
experimental errors. The experimental values for A2 and A4 were entered

into the program which calculated the limits of 0 for each 0 ellipse

Iabl

.415
V|fi

49

 

 

 

 

 

Table IV-lO. Results of angular distribution experiments
at 5.95 and 6.25 MeV.

Ep(MeV) E (keV) A; A: 6

5.95 93.7 -0.002:0.025 —0.015:0.038 a
103.0 -0.065:0.013 0.003i0.020 0.00<6<0.11

6.25 103.0 -0.065:0.010 0.018:0.014 6:0.07b
108.5 -0.017:0.115 0.076i0.l68 0.40<0<5.67
307 8 0.542t0.090 0.049i0.131 0.07<6<0.34
352.2 -0.26-i0.034 0.022i0.047 -0.03<6<0.07
363.0 -0.287:0.027 0.035i0.037 -0.02<6<0.03
410.9 0.641i0.019 0.086i0.027 0.67<6<0.78
424.2 —0.254t0.031 0.012:0.043 -0.31<0<-0.07
455.2 0.300:0.066 -0.082i0.096 -0.14<6<0.14
480.6 -0.283:0.068 0.036:0.095 -2.36<6<-0.02
518.0 -0.l76i0.030 -0.023i0.040 0.21<6<0.47
550.9 -0.173:0.070 0.027i0.099 0.03<6<0.81
574.5 -0.214i0.l48 0.133i0.210 -3.27<6<-0.11

aThe 93.7 keV Y ray loses its angular correlation due to its long

lifetime.

b . .
No error limits were computed as the ellipse dld not pass through the

data box.

8 was assigned by the closest point on the ellipse.

50

 

 

 

Table IV-ll. Results of angular distribution measurements
with Ep = 6.65 MeV.

EY(keV) A; A: 6

92.2 -0.373:0.054 -0.089:0.070 6=—0.03a
103.0 -0.044:0.005 0.001:0.007 0.02<0<0.09

108 5 0.013:0.030 0.028:0.043 -0.11<6<0.02
157.28157.4 -0.214:0.034b —0.044:0.049 0.02<0<0.09b
208.1 -0.376:0.095 -0.086:0.125 -0.12<6<2.05

307 8 0.458i0.016 —0.032:0.022 0.11<6<0.18
352.2 -0.218:0.032 0.044:0.045 -0.09<0<0.00
363.0 -0.272:0.021 0.043:0.029 6=—0.02a
366.8 -0.017:0.031C -0.04010.051 6:0.23 or -9.52‘3"C
404.2 -0.046:0.029 -0.014:0.041 —0.09<0<0.02
410.9 0.563i0.011 0.008:0.016 6:0.73a

424.2 -0.l78i0.004 -0.001:0.005 -O.11<0<-0.07
455.2 0.225:0.023 -0.024:0.033 -0.02<0<0.18
457.2 -0.230:0.014 -0.010:0.020 -0.27<0<-0.14
466.0 0.221:0.020 -0.171:0.030 0=-0.11 or 1.803
480.6 -0.20820.006b -0.0l3i0.008 6=-0.14a’b
518.0 —0.206i0.027 —0.018i0.039 0.34<0<0.81
550.9 -0.168:0.008b 0.01020.012 0.34<6<0.42b
574.5 -0.07410.020 0.050:0.029 0=~11.43 or 0.113
628.7 -0.006i0.014 -0.020i0.020 -0.23<0<0.29
637.9 -0.065:0.024 -0.038i0.035 5=-0.97a
712.0 -0.230:0.023 -0.037:0.033 0.02<0<0.07
778.5 -0.420:0.021 -0.017:0.029 -0.12<6<-0.05

 

 

‘

aNO error limits were computed as the ellipse did not pass through the

data box.

6 was assigned by the closest point on the ellipse,

b
These data are a composite from an unresolved doublet.

c
The ellipse for these J

2

values lie entirely within the data box.

51

Table IV-12. Results of the angular distribution

at Ep = 7.32 MeV

 

 

 

Ey(keV) A A4 0

92.2 -0.208:0.063 -0.045t0.079 —0.03<6<0.11
103.0 -0.034:0.005 0.005i0.006 0.02<6<0.09
108.5 -0.037:0.024 -0.003t0.035 -0.11<0<0.19
157.2+157.4 -0.163i0.0153 -0.004to.021a a

180.9 -0.100:0.034 -0.054:0.044 0:1.38b
208.1 -0.268:0.041 —0.117t0.059 6:0.00b
294.1 -0.374:0.051 0.084:0.079 —0.14<6<-0.03
307.7 0.194:0.019 -0.083:0.023 -0.12<0<-0.03
338.1 052310.100a —0.224:0.13Ba a

352.2 -0.182i0.016 —0.008:0.022 -0.19<6<-0.07
363.0 -0.179:0.011 —0.009:0.014 -0.05<6<0.02
366.8 —0.044i0.016 -0.037:0.021 0:1.38b
395.6 -0.049:0.018 0.004:0.022 0.09<0<0.21
404.2 0.072:0.109 -0.047:0.140 -0.55<0<0.05
410 9 0.47l:0.008 0.028:0.010 6:1.00b
424.2 -0.109:0.007 0.002i0.008 -0.05<0<0.02
432.6 0.489:0.084 0.315i0.106 c

455.2 0.166:0.017 -0.006i0.021 0.07<0<1.19
457.2 -0.160:0.019 —0.017:0.024 -0.23<6<-0.07
466.0 0.111:0.019 -0.033:0.025 6=—0.18 or 14.30b
470.6+471.4 -0.234:0.178a —0.460t0.218a a

480.6 -0.157:0.008a 0.021:0.011a a

550.9 -0.156i0.0123 0.009:0.015a a

574.4 -0.177:0.070 -0.025:0.091 -14.30<0<0.12
590.1 -0.177:0.070 -0.138i0.092 c

621.5 0.280:O.256 0.264:0.270 c

628.7 0.093:0.053 0.027t0.070 -0.38<0<-0.31
637.9 -0.030:0.051 0.028:0.064 O.31<0<3.73
653.9 -0.053:0.079a 0.157:0.102a a

11016 11'-

EIIRGVI

703.0
713.0

763.1
778.5

'4.)
H
*— l
~J

1055.3
\
aTIIQSE d;

10 8110:
data be.

c.
)0 dete
and inc

Table 1V—12. Continued.

52

 

 

 

EY(keV) A; A; 6

705 0 -0.105:0.026 0.106i0.036 -0.02<0<0.05

712.0 -0.200:0.022 0.025:0.031 6:0.12b or
—8.14<6<-5.14

762.1 0.15050.040 0.018:0.051 —0.31<6<-0.12

778 5 —0.458:0.062 0.067:0.075 —2.36<6<-1.28 or
-0.38<6<-0.16

917.7 —0.020:0.035 —0.059:0.047 6:0.60 or -5.14b

1055.3 —0.110:0.034 -0.047:0.045 6=—1.73b

 

8These data were Obtained

from an unresolved doublet.

bNO error limits were computed as the ellipse did not pass through the

data box.

cNo determination Of 0 could be made as the data are of poor quality

and inconsistent.

1135 I

53

*

'k
and A space) which passed

(the loci of 6 form an ellipse in A2 4

nearer the data point than the errors assigned. Also the program cal-
culated the point on each ellipse nearest to the data point giving the
x2 per degree Of freedom for these points. For each Y ray one plot
was produced including the data box (the box formed by the error

bars on the data point) and the 0 ellipses for negative and positive

parity cases for each value of J The input included that used for

2.
the excitation function plus one card per gamma ray containing the
Y's energy, the level energy, the final state spin (as described in

'k * * 'k *
Chapter VII), A2, AA2 (the error in A2), A4, AA4. The spins were
chosen using the 6 ellipse plots, the x2 plots, and the excitation
data, plus overall consistency with other levels. Plots of the

ellipses and x2 can be found in the Appendix and Chapter VII.

116c

ation is
tospin I
little f1
energ)' 51

7.3 1161' 1

The
3f 30 He
lCIiQn 1

1.161, , N e

37111 a 1E
153 Sig:
The

‘6

3‘: Seen

V. THE 118Sn(p,3nY)1168b REACTION

116Sb can be studied via the 118Sn(p,3nY) reaction. This re-
action is of interest because the (p,nY) reaction populates states
to spin 3 or 4 with relatively large cross sections and has very
little feeding to states with spin 5 and greater. Proton of 30 MeV
energy should produce states with twice the angular momentum as the
7.5 MeV protons used in the (p,nY) experiments. Calculations from

13

CSBN indicate that the largest cross section exists for 2:6 for the

(p,3n) reaction.

A. Singles

The 118Sn(p,3nY)1168b reaction was performed with a proton beam

of 30 MeV Obtained from the MSU Cyclotron. The Q—value for this re—
action is -21.76 MeV with the Q—value for the 4n reaction being -29.81
MeV. Neutron cross sections were calculated using the program CSBN
which indicated that the maximum for the 3n reaction would be at 30 MeV.

188h which was rolled

The target used was a 15 mg/cm2 enriched foil of 1
from powdered metallic tin Obtained from the Isotopes Division of Oak
Ridge National Laboratory. Both a Low Energy Photon Spectrometer (LEPS)
and a larger 10.4% Ge(Li) detector were used to accumulate data in the
MSU Sigma 7 computer.

The higher spin states were enhanced, as expected, with spin 5

states being approximately 4 times as strong as spin 1 states, as can

be seen in Figure V-l.

54

Dmlvwv..HN\CInuuzmuv—.

55

 

 

 

[‘829
8 6°OSS
to 0'815
: -4 ’IIS
I-\ I
?" 9'08’7 —
C
. 2°st
0.
Z;— zwzv —
U) 6'01'7 -
10
" 0°£9£
Z'ZSE
L'AOE
17191
O'EOI
1'86
(0 ID 3'
O O O
H H H

 

V'LSI

O'EOI
Z'Z6

 

10

6'055

'IIS

9°08?

2'55?

'12?
6'01?

Z'ZSE
I'BEE

L'ZOE

4‘ p.

 

 

10
10

Comparison of singles from (p,nY) and (p,3nY) reactions.

Figure V-l

1'1

detectc

.1618le

2w

56

B. Gamma-Gamma Coincidence

The target used was the previously described 118Sn target. The

detectors used were an 8% and 9.6% efficient Ge(Li) detector. The
detectors were positioned as in Figure III-2 except the beam passed
through the block which acted only as a Compton suppressor. The
experiment consisted of a typical three parameter fast-slow coinci-
dence arrangement with constant-fraction timing discrimination. The
TAC information was preserved along with the energy information for
later analysis. Coincidence events were stored as triplets of channel
numbers and sorted Off-line using weighted background subtraction.
Approximately 14 x 106 events were collected over a 2 day period.
Although this experiment added little new information to the (p,nY)
reaction, it was able to Offer more and better information on the
cascades among high spin states and corroborate the results of the
existing low energy (p,nY) work. Observed coincidences can be found
in Table V-l and the gated spectra for the (p,3nY) coincidence re-

action can be found in the Appendix.

[3311

57

 

 

 

Table V-l. Results of three parameter Y—Y coincidence
for the 118Sn(p,3nY)116Sb reaction

Gated Y ray Coincident Y rays

(keV) (REV)
92.2 224.0, 307.8, 338.1, 410 9
103.0 157.4, 208.1, 216.3, 307 8, 352.2, 363.0,

550.9

157.2 8 157.4 103.0, 208.1, 352.2, 455.2, 457.2, 550.9
208.1 103.0, 157.4, 352.2, 380.
224.0 338.1, 410 9
307.8 103 0
338.1 92.2, 224.0, 410.9, 546.2a
352.2 103.0, 157 4, 208.1, 426.33
363.0 103.0, 157.2
410.9 92.2, 224.0, 338.1
424.2 480.6
426.38 352.2, 455.2, 546.28
455.2 157 4, 208.1
550 9 103 0, 157.2, 338.1

 

a . . . .
These gamma rays seem to be in ceinc1dence with the

116Sb Y rays but

were not placed within the present level scheme.

is 8 86
large 81110111
ta 8110 ‘81
11.1111 can
timing 1
valved '1:
record a
the p re:

fiIDL‘IlI 1

VI. EVENT RECOVERY

As a part of these and other gamma—ray spectroscopy studies a
large amount of gamma—gamma—time coincidence data have been taken, both
two and three-dimensional. Because Of large coincidence counting rates
which can be Obtained in experimental in-beam studies with nuclei con-
taining rotational structure and the large number of transitions in-
volved in Odd-odd nuclei, we have, upon occasion, found the need to
record and subsequently recover from 50 to 70 million events. With
the present computing facilities, the limitation on recovery is the
amount of core required to contain the spectra. If the core require—
ments become too large, it becomes necessary to store pages of core
temporarily on the disk. The swap time becomes prohibitively large
with a small increase in program size and consequently the data re-
covery was Often very cumbersome and time consuming.

Since a large fraction of the time needed to recover a tape was
consumed in reading, as Opposed to sorting, the total time would be
greatly reduced by reading the tape once and doing all the sorting
at the same time. This cannot be implemented because of the finite
size of core memory, so it was decided to copy from tape to disk storage
and sort it from there with the limit of 12 gates per pass through the
disk file. Storage of the entire tape on disk would require about
5 x 106 words of temporary storage, which is almost never available,
therefore, the data needed to be reduced to the smallest possible
subset as they were transferred to disk. This is accomplished in
two ways. First, if the data are 3 parameter, the TAC half words are

gated immediately using a TAC gate common to all energy gates. The

58

gates

SOIIS

scrted

59

TAC information is reduced to one bit of information which is set to
indicate background and not set to indicate a peak channel. The second
method is to immediately throw away any event whose gating side does
not appear within a gate. This method requires that gates be recovered
from only one energy axis at a time. A rather arbitrary limit of 12
gates sorted simultaneously was imposed, making necessary multiple
sorts from file. To ensure minimum time requirements the gates are
sorted into ten nonoverlapping sets, making possible a maximum of 120
gates for one pass through the tape. An array corresponding to the
range of channel numbers is set up such that the channels not used
contain a zero and those that are used contain a number from 1 to 10
corresponding to the set which contains the gate. The data are then
presorted into ten files using the set number as a file number (with
zeros being thrown away). At the same time, if necessary, the half-
words are swapped to insure the gated side appears first, removing the
need to check again. Each file is then read in turn and sorted as in
earlier programs (with weighted background subtraction for both TAC

and energy gates) with the data being punched at the end of each file
and the core being available for the next set of spectra. A block

diagram Of the program appears in Figures VI-l and VI—2.

 

60

 

 

i1

 

Read tape record

end of tape encountered

——-—-4——u-'-

 

 

 

[none throw
left

pick up event
away all channel #

0

 

 

\

 

set

check TAC
bkg flag if needed

110‘

 

 

 

check if used
in gate

not

 

 

 

 

 

swap so gate
is lst, add bkg
flag

 

 

 

store in
array for file

 

full

 

 

output to file ’

not

used

full

 

 

 

 

 

zero fill all
arrays and
output them

 

 

 

l SORT I

 

Tape reading routine in EVENT RECOVERY.

Figure VI-l.

 

advance
next f i

€1.78

18

61

from tape reading routine

 

 

 

advance to I OF

 

 

 

read file record '

next file 7 I entire
record
sorted

none left

 

 

 

 

get next event

 

stop ' MI '¢

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

all
gates
sorted
event et lst ate
to B 8
left
in gate I check left bkg I 1 I next gate
A
event to right
of gate
1 f
| check peak event to e t ,
. in
event to right
gate
of gate
in gate check right bkg add 1 to —4u
spectrum
6 event to right
subtract of gate
weighted
count

 

 

Sorting routine in EVENT RECOVERY.

Figure VI—2.

Except
the states
icrk. Firs
rep-med 11
11993.7,
the other I

angular dis

VII. DISCUSSION OF INDIVIDUAL LEVELS

Except for the ground state, all spin and parity assignments to

116

the states of Sb as shown in Figure IV-4 are based upon the present

work. First, using the results of the electron capture decay of 116Te
reported in Chapter III, the spin and parity assignments were made to
the 93.7, 731.6, 919.7, and 1158.3 keV levels. The assignments for

the other levels were made based upon the in—beam studies. The Y-ray
angular distributions were used in conjunction with theoretical pre-
dictions of MANDY to obtain the spin assignments, often giving un-
ambiguous choices. Where an ambiguity remains, experimentally determined
cross-section ratios (described in Chapter IV) were compared with
theoretical predictions of MANDY. These were particularly useful when
the state in question was of spin 4 or greater. In cases where more
than one choice remains, the multipolarities of the Y rays are examined
for reasonable and consistent values. The parities of the states are
based upon the beta decay or conversion electrons.

Delta ellipse and x2 plots are shown for those Y rays for which
angular distributions were measured. Energies for level excitation,
gamma ray energy, and proton beam energy are listed along with the
spin of the state produced by the gamma-ray transition. Spins shown
on the different ellipses and x2 plots are the possible values for
the particular state in question. The dotted line on the x2 plots
corresponds to a circle which passes through the corners of the data
box and is given as a reference to indicate which spin may be the

better choice, but is not meant to be a stringent criterion for the

62

 

choice of a g
that all stat

if any pertur

The grout
important be.
Spin (J3) in
determined t
and inferenc
states in 11

The 93_'
3136c. This
iSOtropiC a:
angUIar diS'
confirmed t]
The iDIErna
I Pay to be

 

 

 

 

63

choice of a given spin. It is assumed, except for the 93.7 keV state,
that all states de-excite rapidly enough that there is very little
if any perturbation of the directional correlations.

4.

A. Ground State J1T = 3

The ground state spin is not measured in this experiment but is
important because it is a basic starting point for use as the final

spin (J3) in MANDYll. The ground state J1T has been previously

determined to be 3+ by the atomic-beam magnetic resonance method6,
and inference from the log ft data for its electron capture decay to
states in 116Sn. The results of the present beta decay and in-beam
gamma-ray work are consistent with this assignment.

+

B. Ex = 93.7 keV J" = 1

The 93.7 keV state has a half life longer than approximately 0.2
usec. This long lifetime causes the 93.7 keV gamma ray to have an
isotropic angular distribution. A very careful measurement of the
angular distribution of this Y ray at an excitation of about 400 keV
confirmed that this is indeed the case as indicated in Table IV-6.
The internal conversion work of Fink et_al,5 has shown the 93.7 keV
y ray to be an E2 transition (0K = 1.52). Log ft measurements from

the beta decay of 116Te also confirm that this level has J1T = l+

Previo:
"ark by Ra]
02010.02
tion may b
capture de
h‘a-hnouni's
the 93.7 k
Values fro
therefore
and 4+ for
b." the era
tion data
3.03:0.06 ‘

0:

x“

64

+

c. EX = 103.0 keV J" = 2

Previous internal conversion electron measurements and gamma ray
work by Rahmouni18 gave a K internal conversion coefficient of
0.20:0.02 for the 103.0 keV Y ray, which suggests that the transi-
tion may be E1. When intensities derived from the current electron
capture decay work are used for the 93.7 and 103.0 keV Y rays and
Rahmouni's values are used for electron intensities (GK = 1.52 for
the 93.7 keV Y ray), a value for GK (103.0) of 0.67i0.07 is calculated.
Values from Hager and Seltzer19 are 0.153 for E1 and 0.503 for M1,
therefore the multipolarity must be Ml yielding possible values of 2+
and 4+ for the 103.0 keV state, of which the spin 4 can be eliminated
by the excitation function data shown in Figure VII-1. Angular distribu-
tion data in Figure VII—2 provide us with a mixing ratio of 6 =
0.05:0.06 which indicates that the 103.0 keV Y ray is nearly 100%

Ml.

+

D. Ex = 410.9 keV J" = 4

The 410.9 keV level is depopulated by two transitions both of
which have a large positive A; (Figure VII-3). For the 307.8 keV
gamma ray both the 3 and 4 values are likely. For the more intense
410.9 keV gamma ray, as shown in Figure VII-3, the values for the
Spin are more likely to be 4 or 5. The J = 5 value can be eliminated
as that would require the 307.8 keV gamma ray to be 6% M3 and 94%

E4 which is very unlikely since this transition is not delayed by

the amount expected for such a high multipolarity. The positive

parity can be assigned on the basis that the observed mixing (6 = 0.73)

00M

 

Relative Cross So cti on

65
Figure VII—I

 

 

 

 

f
h. M

AA_LL1‘ ‘u
"' j'j'

fiT

W

l03.0 keV J 455.2 keV J

_.‘I. i

T “0.,
r- t‘ ' : ‘ : 1 : ' I '0
1 ‘Jgi l '
. ”- 1', 1
I

!:-'::I 4.3-2
0- - 2 +
b 0 out
.. '3 0
b a d
" 1

4

5

 

 

 

4|O.9 keV

b

 

 

6.0 Ep (MeV) 70

Excitation functions for 103.0, 410.9,

““L

460.0 keV J

 

 

 

 

 

7.0
455.2, and 466.0 keV levels.

6.0 13p (MeV)

b)

RELATIVE 11.-

h

 

00 EL-

 

66
Figure VII-2.

 

RELATIVE x'
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A?

 

 

 

 

 

 

  
    

    

 

 

 

 

 

 

 

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93.7 KEV

A; 1

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“was 4150 4132 Again 012 690 0.8-6.3} ~03 “in 10:2 6.» as

Chi square and delta ellipse plots for the 93.7 and 103.0 keV gamma rays.

r

 

'LIP w>HF(JmDHI

0» EL-

50 J§=2

uh

67

Figure_VII-3.

 

 

 

 

 

‘ V

 

 

 

 

 

 

 

 

 

 

 

 
    

 

 

 

 

 

 

  
   

 

 

 

 

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'14-’03 4.30 432 ,g' (in Ea 6.9 as 41.1» -of2 A; alo 5.2 6.4 0.5

Chi square and delta ellipse plots for the 307.8 and 410.9 keV gamma rays.

for th:
El and
assign:

Co:
tion r
the 41

relati

68

for the 410.9 keV Y ray would be expected to be highly unlikely for
El and M2 transitions, which would be required for a negative parity
assignment.

Comparison with theoretical estimates of single particle transi—
tion rates for Y-ray de-excitation indicate that the M1 component of
the 410.9 keV y ray is hindered by a factor of approximately 1600

relative to that of the E2 component.

E. EX = 455.2 keV J = 3

An unambiguous assignment can be made for J = 3 for this level.

The Y—ray angular distribution for the 352.2 keV Y ray has a fairly
*

2

and far from the other ellipses, except for that for J = 2, however.

large negative A which places it on the J = 3 ellipse (Figure VII-4)
A spin 2 can be eliminated by the excitation function data which is
shown in Figure VII-l. The value for 6 gives 96% E1 (M1) and 4% M2
(EZ) for the 352.2 keV Y ray. The other branch (455.2 keV gamma

ray) was somewhat weaker and more difficult to analyze, however,
there exists a minimum in x2 for J = 3 giving 100% E1 (M1).

A half life of 1.85:0.06 nsec was measured for this state as
described in Chapter IV Section C. This indicates either a i-forbidden
M1 or El. Seven states lie above the 455.2 keV state which de-excite
through cascades which terminate on the 455.2 keV state and bypass
other states. This possibly indicates a difference between the
character of these eight states and the other excited states. It
is felt that thermxstplausible difference is that these states are

negative parity states constructed from the neutron orbital hll/Z'

"l h“lrlll' .uI

 

 

RELATIVE x.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  
  

 

 

 

 

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Chi square and delta ellipse plots for the 352.2 and 455.2 keV gamma rays.
Figure VII-4.

The
relati‘
from tl

rates.

distri
a rela

as sho

ES to:

Estim—

G

70

The 455.2 keV branch is hindered by a factor approximately 9.8
relative to the 352.2 keV branch compared to what would be expected
from the branching ratio based upon Weisskopf single particle esti-

mates.

F. Ex = 466.0 keV J = 3

The 466.0 keV state also exhibits the behavior of the angular
distribution for the 363.0 keV Y ray, the most intense branch, having
a relatively large negative A; giving an unambiguous choice of J = 3
as shown in Figure VII-5. The 466.0 keV Y ray is too weak to be of
any value in the determination of J from its angular distribution
data. Our excitation data (Figure VII-1) give a very good fit for
J = 3.

The 466.0 keV branch is hindered by a factor of 17.1 relative to
the 363.0 keV branch (assuming that the 466.0 keV Y ray is 100% M1)

as compared to what would be expected from Weisskopf single particle

estimates.

G. EX = 503.1 keV J = 5

The 503.1 keV level depopulates via the 92.2 keV Y ray, which
cannot be resolved from the 93.7 keV Y ray at low excitations.
Figure VII-5 shows that the angular distributions are inconclusive,
possibly allowing values of 3, 4, and 5 for J. However the data
from the excitation function give a reasonably good fit to the cal-

culated values for J = S as shown in Figure VII-6.

r V H 2
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“‘90.: ~03 -0f2 A; 020 0.2 0.» 0.3 -53, 02 A; 020 0.2 0.» 0.:

Chi square and delta ellipse plots for the 363.0 and 92.2 keV gamma rays.

Figure VII-5.

.5‘

D

L

ChibUUW

~5.

.0050

h .

0>~h°~0~l

 

 

Excitation functions for the 503.1, 517.9,

 

 

 

 

 

 

 

 

 

Figure VII-6
J rJ
.5030 keV 0 550.9 keV l 0
_ 2
L 0
3
b /
» /
f0: 4
8 * i 5
i
J; 6
§ 507.9 keV J 574.4 keV J
5 h. l I d
o L l
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3 H 2
a:
h-
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If
L
ii
5* 3
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/ IF
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. L L . L 3 5+5
4 a vvvvvv __ 6 J
6.0 E, (M) 7.0 6.0 Ep (MeV) 7-0

550.9, and 574.4 keV levels.

73

H. Ex = 517.9 keV J = 2

The 424.2 keV branch from the 517.9 keV state has a large negative
A; (Figure VII-7) which allows an assignment of J = 2. The 518.0
keV Y ray is somewhat weaker and overlaps some with the 511 keV
annihilation gamma peak. The data for this gamma ray, as shown in
Figure VII—7, allows J = 2,3,4. Excitation function data (Figure
VII—6) indicate that this state has a higher cross section than
calculated for J = 3 or 4 but not quite enough for J = 2. It is felt
that the measured values are, however, a good indication of J = 2.

Thus, a spin assignment of 2 for the 517.9 keV level can be justified.

I. EX = 550.9 keV J = 2

Three transitions depopulate the 550.9 keV state, of which two
(457.2 and 550.9 keV) give useful angular distributions. The 550.9
keV Y ray at an excitation of approximately 700 keV is relatively free
of contamination by a Y ray of the same energy from a level at 654.1
keV. The fit to theory indicates possible values of J = 2, 3, and 4
(Figure VII-8). The 457.2 keV Y ray is too weak for analysis at
this excitation but an an excitation of approximately 1.1 MeV it has
an excellent fit to J = 2 as shown in Figure VII—8. Excitation
function data, Figure VII-6, show that this level is characteristic
of J = 2. Also the depopulation of this state is to three different
states having J values of l, 2, and 3. Therefore, it is felt that

J = 2 is the best choice for the spin for the 550.9 keV state.

  
  

.
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Chi square and delta ellipse plots for the 424.2 and 517.9 keV gamma rays.

Figure Vll~7.

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Chi square and delta ellipse plots for the 550.9 and 457.2 keV gamma rays.

rigure VII-8.

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76

J. Ex = 574.4 keV J = 2

Only the 480.6 keV transition from the 574.4 keV level gives an
unambiguous angular distribution as shown in Figure VII-9. The
other three Y rays are too weak to be useful as shown in Figure VII—9
and Figure VII-10. The 480.6 keV Y ray has a fairly large negative

*

A2 making the choice J = 2 most likely. Excitation data (Figure VII—6)
also are a reasonable fit to J = 2. The depopulation of this state
produces states with J = l, 2, 3. The best choice for the spin of

this state is 2.

K. EX = 612.5 keV J = 4

The 612.5 keV state is depopulated via the 157.4 keV Y ray.
Difficulties were encountered with nearby Y rays when fitting the
data. Special care was taken to separate the 158.5 keV Y ray (from

the decay of 117

Sb) from these data. The 157.2 keV Y ray from the
731.6 keV state could not be resolved and in the angular distribution
measured at 6.65 MeV it contributed about 30% of the total intensity.
The angular distribution measured, Figure VII-10, allows J = 2, 3,
and 4 although it must be assumed that this measurement is perturbed
somewhat by the 157.2 keV transition. The excitation function data,
shown in Figure VII-ll, which are corrected for the intensity of the
157.2 keV Y ray are a reasonably good fit to J = 4. On the basis of

the excitation data and the angular distribution, we have made the

assignment of J = 4.

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Chi square and delta ellipse plots for the 480.6 and 108.5 keV gamma rays.
Figure VII-9.

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Chi square and delta ellipse plots for the 574.5 and 157.4 keV gamma rays.
Figure VII~10.

6|

Kalb.

UWOLU

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Cross Se ctlon

Relative

79

Figure VII-II

 

  

 

 

 

 

 

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Excitation functions for the 612.5, 654.1,

 

E (MeV) ..O
D

731.6, and 815.1 keV levels.

dcub

T L-
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I

80

L. Ex = 654.1 keV J = 3

For the 654.1 keV level the excitation data (Figure VII—ll) give
a good fit to J = 3. Neither the 653.9 or the 550.9 keV branch is
able to give a good angular distribution as the 653.9 keV Y ray is
much too weak, and the 550.9 keV Y ray is part of an unresolvable
doublet. At an excitation of 1.0 MeV approximately 45% of the 550.9
keV doublet is produced by the decay of the 654.1 keV state.

4.

M. EX = 731.6 keV J" = 1

The beta decay log ft of 5.5 indicates that this level probably
has J1T = 1+. As shown in Figure VII-12, the angular distribution
measurements of the 628.7 and 637.9 keV Y rays are in agreement with
this value. The 157.2 keV transition which constitutes 9% of the
decay of this level, is part of an unresolved doublet. The intensity
for the 157.2 Y ray was calculated from the intensities of the gamma

rays which depopulate the 574.4 keV level in the beta decay studies.

N. EX = 815.1 keV J = 3

The angular distributions of the 712.1 keV gamma ray shown in
Figure VII—13 has a very good fit for a J = 3 assignment to the 815.1
keV state, while that for the 404.2 keV Y ray allows values of 2, 3,
and S for the spin. The excitation function data, shown in Figure
VII-ll, clearly indicates J = 3. The minimum in x2 for J = 3 yield
mixing ratios which indicate that both branches are nearly pure

(2 99.7%) M1 (El).

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Chi square and delta ellipse plots for the 628.7 and 637.9 keV gamma rays.
Figure VII-12.

r flfM/MV.

lull. MU>HL‘<IUN‘

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Chi square and delta ellipse plots for the 404.2 and 712.1 keV gamma rays.

Figure VII—13.

The
indicati
Ell-15.

the-3r)? w

The

i5 Yew

fumztion

83

0. Ex = 820.6 keV J = S

The angular distribution data are inconclusive for this level
indicating equal likelihood of J = 2, 3, 4, or 5 as shown in Figure
VII-15. Excitation function data in Figure VII—l4 show a fit to the

theory which is consistent with J = S.

P. Ex = 841.1 keV J = (6)

The 841.1 keV level depopulates via a 338.1 keV transition which
is very weak and which also has nearly the same energy as a contam-
inant Y ray from our lead beam stop. The intensity is much too low
for measurement of angular distributions, however, the excitation

function data, shown in Figure VII—14, indicates the spin may be 6.

Q. EX = 881.5 keV J = 3

The angular distribution of the 778.5 keV Y ray shown in Figure
VII-15 indicates that only the J = 3 for the 881.5 keV state is a good
choice. The excitation function data tend to confirm this value as
is shown in Figure VII-14.

+

R. EX = 917.7 keV J1T = 1

The 917.7 keV level is observed to be fed in beta decay with a log
ft of 6.3, which indicates an allowed or first forbidden transition.
Since the angular distributions (Figure VII-16) are not isotropic
and are in agreement with J = 1, an assignment of 1+ is made to this

level, as no shell model configurations exist for the l- possibility.

82

mu

”
\a
u
5
av
-

-

9k

C van So cflon

Relative

VII-l4

 

88L5 keV

 

 

 

 

 

 

SIR? keV

/‘

 

Figure
820.6 luv J
I
2
b o
3
L I
L 4
5
.4..41H —» - - 6
84L! nv J
l
b 2
O
L
L
3
. / 4
-aLe:+5
x4- ' ' I 6
6-2 Ep (MeV) 7.0

Excitation functions for the 820.6, 841.1, 881.5, and 917.7 keV levels.

6.4 Ep (MeV) 7.0

 

Z

 

-dP ”>Hh:(luull

85

t V ' v a V T '— v j

//~\\(

.. /\
“‘v ' .
9 V,

 

 

 

' RELATIVE x'
V/

 

 

 

 

 

 

 

          
   

 

 

 

 

 

 

 

 

2.
3
-so -eo -3o o so so -eo -éo ‘o éo so so
u fl - - - - mama) - - _ - f
E, «.5 rev 6 specs rev 4
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£1- 7785 KEV
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-3 4
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-06 P 1
-JB r 2+ l '(x§£2~ 4

 

A'

 

 

 

 

“ -0.‘I -0.2 A: 0.0 0.2 03 0.3 4."! 4.2 h', 0.0 0.2 0.9 0.:
Chi square and delta ellipse plots for the 208.1 and 778.5 keV gamma rays.
Figure VII—15.

-n’ U,HP‘JH‘

 

2+

'5‘ z

.3>

86

 

 

 

flflJEWEI?

 

|
“4

 

 

-s‘o-éo-éo ‘oéo
w

 

 
     

 

 

QHGSSNHV
‘3 EU'SPVWEW

 

.0
.8
la)

5509

a i J
"3* 0.0 U

-o.e -35. 4.5,;oio oi: is os-oic -mi,gdo olz is as

 

 

 

 

'9
C

 

 

 

 

 

Chi square and delta ellipse plots for the 366.8 and 917.7 keV gamma rays.
Figure VII—16.

87

The excitation function data in Figure VII—14 show only that the cross

section is too high for J 3, and does not distinguish between J = l

or 2.

CD
[Tl
II

948.0 keV J = 4

The 294.1 keV Y—ray branch of the decay from the 948.0 keV level
*

has a large negative A2

which allows an unambiguous choice of J = 4,
as shown in Figure VII-l7. Excitation function data indicate a spin

of either 4 or S.

T. Higher Excited States

Fifteen levels were placed using y-Y coincidence data, at excita—
tion energies ranging from 992. to 1481.1 keV. Although excitation
function data and angular distribution data were collected at suf-
ficient excitation energies to produce these states, only three
states (1127.2, 1158.3, and 1222.9 keV) have analyzable angular dis—
tributions, and most fail to have sufficient data from the excitation
function measurements to allow spin assignments to be made with
any degree of confidence. These excitation function data are shown
in Figure VII-18.

The 395.6 keV transition from the 1127.2 keV level has an analyz-
able angular distribution as shown in Figure VII-l7, which indicates
a spin of 2.

The 1158.3 keV level is observed to be fed in beta decay with a
log ft of 5.4 which indicates an allowed transition with the Spin

and parity of the level being either 0+ or 1+. Only one of the

88

 

   

 

  

 

 

 

 

 

 

     

 

 

 

 

 

 

 

'3
5

+ _
‘v bl
a v ’ " ‘ 3
*- ‘ ’ \
5 b -- b-------
as "’ 3 2’ l

{+--—---- —-———----4 I

4 F 1
A A A L A ¥ A A2 A A
‘flSD ‘fiCD 'H30 0 430 3" 130 '4HD «#30 0' «ID ‘50 :so
u j g - g - muml - j g -
(”7an g-uzuEV
3, EL- mu KEV 5 4, EL-n27.2 KEV 1
£1- ZS‘IJ KEV Eo- mom 3

.3» kg-a‘ 4» £01. 4

i U 4
.s 4
‘2? 4+ 2 4
0” J» I 4
“1* H g ”27.2 4
‘o" 4} J
..‘P 4» 4

I+ y 73:5

.3» 4L 1

 

 

 

 

”as -o.V -o.2,g|o.o o: M 03-03 42‘” o: M u
Chi square and delta ellipse plots for the 294.1 and 395.6 keV gamma rays.
Figure VII—17.

Cross Section

ReIOfive

8‘)
Figure

VII-IS

 

I r r I

l045.l keV

r I

"58.3 keV

q

N
(”-501 o N

4

 

 

 

 

'r

‘4'

4
(null)

9*;
T

“27.2 keV |222.9 keV J

I
b I a:
b 2 "'
b 2 a:

0

0

b '1
1 3

 

(”OI-D u

 

 

 

 

6.6 Ep (MeV) {,0 .

Excitation functions for the 1045.1,

levels.

1

6.8 Ep (MeV) 7.2

1127.6, 1158.3, and 1222.9 keV

90

three Y rays de-exciting the 1158.3 keV state (1055.3 keV) has an
analyzable angular distribution as shown in Figure VII-19, which
indicates that J = 1, 2, or 3 are all possible values for the spin.
Since the angular distribution is not isotropic and the beta decay
is allowed, an assignment of 1+ is made to the 1158.3 keV level.
The angular distribution of the 705.0 keV gamma ray from the
1222.9 keV level, shown in Figure VII-l9, indicates the most likely

value for the spin is 3.

91

 

RELATIVE x.

 

 

 

 

 

 

A A

 

 

 

 

 

 

 

 

 

 

 

 

 

   
  

 

 

 

 

 

 

   

 

 

-so -so ~50 0 so so so -so -§o 0 so so
1.0 i fl - - AHCTANII) 1 1 -
s, -7.32 HEV a, -7.32 HEV
.9. EL-uss.3 KEV 4 EL-1222.s KEV 4
E1-1055.3 KEV E‘l- 7os.o KEV
.s’ 4'3"?“ tag-2*
.s’
.2»
-.o ,
.3 #
-.2r 2 “58.3 2 l222.9
.J.’ p 4
-.S p U U 4
-.a» 2‘4 403.9 2 45'72.
-1.o 4 L - h - 4 - - - e
o.s -o.s -o.2 A» 0.0 0.2 o.s o.s -o.'+ -o.2 A; on o.2 o.s

0.8

Chi square and delta ellipse plots for the 1055.3 and 705.0 keV gamma rays.

Figure V4i-19.

VIII. SUMMARY AND CONCLUSIONS
The Y-ray decays of the excited states of 116Sb below 1.5 MeV
of excitation have been studied via the electron-capture decay of

l
16 116Sn(p,nY)ll6Sb reaction. Nineteen of the

Te and the in-beam
Y rays observed in the in—beam studies were also observed in the elec-
tron-capture decay. The Ge(Li)-Ge(Li) Y—Y coincidence technique used
both on- and off-line was very useful in the placement of Y rays in
the level scheme. Many weak Y rays were placed in the level scheme
with the coincidence information which otherwise might not have been
placed. Also, the coincidence information is very useful in the
determination of which Y rays are doublets. There appear to be at
least ten pairs of Y rays, some completely unresolvable, which are
within one keV of the same energy. These unresolvable doublets caused
many false starts in constructing the excited state level scheme.

The combined use of cross-section ratios and Y-ray angular distribu-
tions is an excellent method of determining unique spin assignments up
to approximately one MeV of excitation. The Y—ray angular distribu-
tions are very useful for states with J = l, 2, 3 and sometimes 4,
as these states are fed strongly enOUgh that very accurate measure—
ments of their intensities may be made. Those states with J33 are
well suited to cross-section ratio determination of their Spins, as
the relative differences between theoretical predictions are larger
for these spins. Neither method can be used to determine the parity
as the experimental errors are much larger than the required sensitivities
needed to make parity determinations. There appears to be a breakdown

in the ability of MANDY to handle relative cross-section ratios at

92

93

excitations above one MeV, as the experimental values are much less
than predicted in this region. A possible explanation for these devia-
tions is that above one MeV many levels exist which cannot be dis-
tinguished with our present methods and therefore these levels cannot
be used explicitly as extra exit channels in MANDY, thereby causing
the predictions for the observed states to be much too large.

Although the results reported here produce some new insights
into the systematics of this region near the 2:50 closed shell,
more information is needed before a good understanding of the be-
havior of the nuclei in this region can be obtained. The shell model

16

structure of the states of 1 Sb cannot be inferred from the available

data. With more data on this nucleus (e.g. internal conversion elec-

tron data) and systematics of the other Sb odd-odd nuclei the struc-

ture may become more evident.

REFERENCES

10.

ll.

12.

13.

14.

15.

16.

17.

18.

19.

20.

REFERENCES

D. 0. Elliot et_al., Phys. Rev. 5, 202 (1972).
W. B. Chaffee, Thesis, Michigan State University, 1974.

B. G. Diselev, V. R. Burmistrov, Yadern. Fiz., 8, 1057—62
(Dec. 1968).

O. Rahmouni Le Journal De Physique, 29, 550 (1968).

R. W. Fink, G. Anderson and J. Danstele, Arkiv. Fysik., 19,
323 (1961).

C. Ekstrom et_al., Nucl. Phys. A226, 219—228 (1974).
W. Hauser, H. Feshbach, Phys. Rev., 81) 366 (1952).
E. Sheldon and D. M. Van Patter, Rev. Mod. Phys., 383 143 (1966).

E. Sheldon and P. Canterbeing, J. Appl. Math. Phys. (ZAMP)
18, 397.

E. Sheldon and R. M. Strang, Comp. Phys. Comm., 1, 35, (1969).

MANDY computer program written by E. Sheldon and D. M. Van Patter,
Rev. Mod. Phys., Vol. 38, #1, Jan. 66.

K. L. Kosanke, et_al:, Annual Report, Michigan State University
Cyclotron, page 45 (1970,71).

CS8N T. Sikkeland and D. Lebeck University of California, Berkeley.
Oak Ridge National Laboratory, 1972 Mass Compilation.

R. S. Hager and Seltzer, Nuclear data, Vol. 4, Numbers 1 8 2,
Feb. 1968.

E. A. Auerbach, 'ABACUS-II', Brookhaven National Laboratory,
Preprint BNL-6562.

F. Perey and B. Buck, Nucl. Phys. 32, 353 0962).

O. Rahmouni, Compt. Rend., Ser. A 8 B 267: 736,8 (Oct. 7, 1968).

Edited by K. Siegbahn, Alpha—, Beta- and Gamma-ray Spectroscopy,
Vol. 2, page 905, R. E. Bell.

 

GADFIT, computer code written by R. A. Warner, Michigan State
University Cyclotron Laboratory, unpublished.

94

21.

22.

23.

24.

25.

26.

27.

28.

29.

30.

31.

95

J. T. Routti and S. G. Prussin, Nucl. Instr. and Meth., 22,
125 (1969).

F. Perey, Direct Interaction and Nuclear Reaction Mechanisms,
(Gordon and Breach, Science Publishers Inc., New York, 1963).

R. C. Greenwood §t_a1,, Nuclear Instruments and Methods, 17
(1970) 141, 158.

R. G. Helmer et 31., Nuclear Instruments and Methods 96.(1971)
173,196.

J. B. Marion, Nuclear Data 51» 3014319 (1962).

R. J. Gehrke, et_al,, Idaho Nuclear Corporation, Idaho Falls,
Idaho.

G. Berzins and D. Berry, private communication.
G. Berzins 33.31., Nucl. Phys. A104, 241,262 (1967).
R. Helmer, Phys. Rev., 155, 1263,4 (1967).

M. H. Brennan and A. M. Berstein, Phys. Rev., 120, Number 3,
927,33 (1960).

J. P. Schiffer, Annals of Physics, 66, 798,809 (1971).

APPENDICES

96

APPENDIX A

Integral Coincidence and Gated Spectra from the

Beta Decay of 116Te.

 

 

Figure A. Integral coincidence and gated spectra from the beta

decay of 116Te. Background subtraction using the

adjacent continuum has been included.

97

'rrr
>

 

 

 

 

wuwmucwl mmuo sum 0
H > w n HcHH

P D

1 . . . .
'
9
Z
8 (3
o All k
.L rt «7 M
. no ,6
v /_ E
S o 0
6 u /_
r1. S
I Z u
.6 .
(0
CL S g I
. U TL 0
‘ TL er.
U - O
Hmummucwu> >moom mum: we
oHH
P P 0
I . 4 q
r
U
S
f/ .r/
C6 0 .
. . /_ T. 6
n . Co Co
I g o
I T. T. . I.
6 9 TL
I CL S 9 Tl
76 Z u S T.
6 . u 9
(c S S T.
a I u 0
S T. (L
I S u o o
u .0

Figure A.

 

 

 

98

 

 

 

4
4
E'SSOI

 

mumw >mx o.moH

mumw >ox o.omH

mumw >mx o.mom

mama sax m.©em

P

6'099

6'095

Z'LSV

 

 

 

'8OI

S

 

I
0
CC
0

A

 

 

Figure A - continued.

99

rial ..

 

.wh

 

 

 

114‘}

 

 

“.. . . . .-nfi..¢r.. _
mums sax w.ass
some >8: N.amq

mumw >mx c.cws

mama >4; a.0mm

8°99£

8'998

 

TL
8
O
6

‘

6°081

Z'LSI

 

6'081

Figure A - continued.

A

 

 

100

 

mama >mx s.sam

:..... . u . . _

mumw >mx w.mwm

D
4 4 44 4 ‘4 4‘ 44 44 44 ‘4

mumw >mx n.mmo

waaw >mx m.mmo~

 

T.
C...
A
Z

 

 

 

OTEOI

 

 

 

44t1414I4I:4III:III||||||4|\\\\144

Figure A - continued.

101

APPENDIX B

Integral Coincidence and Gated Spectra from the in-beam

1

 

l6Sn(p,nY—Y)ll6Sb Reaction at beam energies of 7.3 and

 

11.75 MeV and the ll88n(p,3nY-Y)ll6Sb Reaction at 30 Mev.

 

Figure B—l. Integral coincidence and gated spectra from the in-beam

116Sn(p,nY-Y)1168b reaction at 7.3 Mev.

102

 

 

157.4 kev gate

 

 

 

 

   

Q) _
U 1
CO
00

> c
O.)

x i

m .

g; .

4—4 :

i

.I

J

J

T.

A

.a

1

, -‘

0 9E ;
i

J

.3

.J

O'EOI ——
__J

A A

103.0 keV gate

V'LSI

E'SSOI

 

 

us 'E6ZI
>
(I)
2
M
.4
II
0..
LL}
L;
O
“-4
H .US
53 286
00
G)
u
C‘.
4 4—4
4
1
.1 L 8Z9
: 6' 99
1 0
J '119
j 9'08’7
j 2'72?
1 (you;
01:92
Z'ZSE
47191
O‘EOI

 

 

 

Figure B—l.

 

103

 

 

 

 

 

 

 

 

4
4 . J
- 4
4 4
1 4
4 “_
J I
4
:-’ 8 8
so w ’ 3 &
> > - > >
,3; 6'SZOI jg __ g; g
N [\ -4 <1: «5
”m“ :2 ._ a g
1;
1'069 g
f 6'OSS
4?
.3 ‘
6'886 ': ;
_ Z‘ZSE ;
‘- °S°s .‘
I'8OZ . 1---; -
T'LSI “I 7191
mm 0m :1! “0‘
4‘
\ L A A A A A A A A A A A A

 

 

Figure B—l continued.

 

104

 

404.2 keV gate

 

6°E7fv

 

8'£O€

 

OJ 0)
U H
CO (0
OD DC
> :>
Q) Q)
.54 .M
\D 00
u; «S
C\ \O
m m
6°8£9 -
[’8Z9 7
i
O'EOI

A A A A A A

Figure B-l continued.

 

Z'lSV

O'EOI

363.0 keV gate

{'048 4

I'Z9l4

 

 

 

 

105

 

 

 

 
  

 

 

 

 

p. .
r449 35.. u L?
1444114 144444 4411 . . . a 3. .1....¢4..4.4 1441144....‘J. era-1.414.. .411..c111:.! 4‘. 6.14.
T A
6
z
v . A
Z
hu/
4 /_ .
O .7
o 0
v 9 .7 .
38 >3 903 z
4 l4 4444 I 444 44*! 44 4444 44! , . .. ...I‘Il11‘4.11 i.141‘1!‘1¢v.11441a1 . .
r 00 _ i
,6 Q, Q” ,6
O I. ..|. E
I. . C. .
v o g o ,— .
L I
A
v 0 .
g
. .r/
. 0 w .
mama >mx N.smq .
9
. a
v A
v A
r 4
v A
oumm >mx w.mss
. 00 I. i
l. 8
.7 S
v I. 9
V
CC
9
. m .9
«Em >4 . 8
g N E

 

Figure B-l continued.

106

 

“l¢l“11 1“ ‘1 ‘ {‘114‘1 ‘11}

 

1 ‘1‘1

mumw >mx c.0wq

 

 

 

 

“‘ 1 ll! 1“! [‘1 “‘

mumw >mx o.omm

i E :3

 

€5'()SS

6'01?

 

CL
0;
9
8

 

O'EOI

 

O'EOI

 

 

Figure B—l continued.

107

 

‘A‘J‘ ‘ ‘ “ ‘1 ‘1‘ 1" ‘fl‘ “l‘1‘11‘11‘1

 

 

TL
0
CL
0

mumw >mx N.m~o

.. ~.. .

 

 

6'OS§
9'S6E

mumw >mx o.~mo

 

 

 

1114 447

‘i‘ 1‘1 4‘ _
4< 4 141.1 - 1.1 141 41414141111141.3111

A

6'LI§

 

Z'VZV

mumw >mx o.mo~ A

 

 

()7E131

gm 2 2:

 

 

Figure B-l continued.

 

 

T___ *a.‘

 

 

 

r

 

lqt<111dlq l‘l 1 III 4

mumw >mx _.NoN

mumw >mx o.mmm

mumw >mx d.m~m

i E 2;

 

6'099

9°087

Z'LSV

Z'VZV

0"EFBE

‘_: rd

 

 

 

A

A

 

Figure B-l continued.

109

 

Z'ZSV

 

6'099

mumw >mx N.¢Nm

6'LIS

Z'VZV

mama >mx N.Noo

.‘ - , t s Q a... ‘. _ - I . ‘ a. ll ‘ Q
. . . _

 

Z'ZSE

muww >mx m.mm0~

a g :2: I...

 

O'EOI

 

 

 

Figure B-l continued.

 

 

110

Figure B—2. Integral coincidence and gated spectra form the in-beam

116Sn(p,nY-Y)ll6Sb reaction at 11.75 MeV.

111

 

108.5 keV gate

O'E9E

D'EOI

 

 

. l J u

1“ JunUl--LA4- ..I .. _

 

 
 

103.0 keV gate

 

 

92.2 keV gate

5‘01?

 

I'BEE

 

L'LOE

-J»‘|IIAL

I

‘A‘.

'119

 

 

'E6ZI

X-axis integral

'OE6 .

['829

6'099

0‘
mo O\'T
MMr-JN

1'802
V'LSI
'EOI

 

 

Figure B-2.

112

 

 

 

 

 

Q)
t; 3% 3 ‘3
°° on go 30
> > > >
3 .3 .3 .3
F: O H r
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2 $97 Z'SSV
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Figure B-2 continued.

 

113

 

 

11¢ 14113111441114

. 1. 1.. .q- ..-.. . , ._. ..-1..Q1..d.i¢-Iifi

'Z6

Z

0°€OI

mumw >mx 5.50m

 

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mumw >mx H.wmm

 

 

1 11> g b»..- tr 1 .-

 

7 L91
O'EOI

mumw >m3 ~.Nmm

.
4111 - l 411 {1113'

S'IZ9

9'801

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mumw >m3 o.mom

A

 

 

 

Figure B—2 continued.

 

 

404.2 keV gate

6°OIv

 

395.6 keV gate

114

388.9 keV gate

['829

1 b

Z'ZSE

I'SOZ

O'COI

 

Figure B-2 continued.

366.8 keV gate

 

6'099

Z'LSV

 

 

115

 

 

 

.41-“. :1!

1‘1!“.l"i 1“

c .v . . “‘li‘¢. - A “1Jl1 .

 

9'OLV
Z'VOV
I'BEE
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'Z6

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7°LSI

.
C...
0

mumw >mx w.mqq

9°08?

 

 

Figure B-2 continued.

116

 

 

 

I
S
I.
mumm >mx N.mmq w,
. c . 44 ~ . q. a .‘ ._.. .. . a. c. .c 1‘s. u... ‘.--AI.J..4..O «1‘ 1 44i~.]¢.- . . A- I
. . fl. .. .2... q .fiwflfl- .J.
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T. (L
m. Wu
mmumw >m3 c.35q a ©.oNq ,o

 

 

 

 

a. 15 . all J ‘0 1 is .c 'n .I ‘i‘!<‘11 ‘1—‘flq
. .

.
k

 

I'Z9L

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1 2°72?

8'99E i

mumw >mx m.onn

TL
g
I.
Z

 

Figure B-Z continued.

 

T'V6Z

O'ECyt

 

117

 

 

 

mumw >m3 5.05m

mumw >mx H.0om

Z'ZSE

 

mumw >m3 m.NHo

. : _ _. _ . . . ._ .;.a.:
, .,.. _

 

mumw >mx m.H~o

r

 

 

t» O
o,
E
my

 

Figure B-Z continued.

118

 

mumw >mx m.mmo

mumw >03 o.mo~

‘

mumw >m3 o.-~

a

mumw >m3 m.mma

.-;:-..Js .a:..::q;q.l4;.

I
no
CL
wu
J_w._;_.f__. .mi; :1
. m.

A

 

 

TL
0
CL
0

 

 

 

r

Figure B-2 continued.

 

119

1025.9 keV gate
868 6 keV gate

 

Z°ZSE Z'ZSE
V'LSI
O'EOT O'COI

 

Figure B-2 continued.

120

Figure B-3. Gated spectra from the in-beam 118Sn(p,3ny-Y)ll6Sb

reaction at 30. MeV.

121

 

11311114114141 113%
4
Cu

mumw >m3 N.No

mumw >m3 o.mofi

 

muaw >m3 «.5mfi

 

 

mumw >m3 H.woN

 

.r/
TL
0
6

L'LO

 

 

V'LSI

Z'ZSE

 

 

Z'ZSE

 

 

Z’ZSE
T

7'1

 

 

’

Figure B—3.

122

mum» >mx o.q-

 

mama >m3 N.~om

mama >m3 H.wmm

 

 

1‘11‘1!‘ 1‘1

mumw >mx ~.~mm

by

6'OIV

6'01?

qSLII

I'BEE

_

.12}:

Z
Z
V
0

T'QOZ

 

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.1..

O'EOI
Z°Z6

 

V'LSI

O’EOI

 

Figure B-3 continued.

 

 

123

O'EOI

mama >mx o.mom

 

 

‘ 1 {‘14 1‘1“} 1‘}

 

z A
— Z
.7 ,0
Co . 7v .
C. no .
Ru .6
T. cu T. .
u Co
C.—
mumw >ox $.0Hq C. .

. a _ é _ ._..

 

 

mumw >mx N.qNa

Z'ZSE

 

 

T.
S
L
o

h/

mama >a3 “.mmq

 

Figure B-3 continued.

Figure C-1.

124

APPENDIX C

Angular Distributions of the Various ll68b Y rays

Obtained from the 116Sn(p,nY)ll6Sb Reaction with

pp: 5.95, 6.25, 6.65, and 7.32 MeV.

 

Gamma—ray angular distributions obtained with the
proton energy at 5.95 Mev. The solid line represents
the least sqares fit to W(8) as explained in the text.
The fit is normalized to 1 at 900. The data in the
lower right is normalized to the isotropic 93.7 keV

gamma ray.

125

 

1.1

103.0 keV

  

   

 

 

)-
k 1.0.!
5
u:
p.
2:
r4
—0.065:0.0l3
.9. I IA: = 0.003:o.020
Ll: 93.7 keV 103.0 keV (N=93.7 keV y)
>' LJ). I I, I
’- I
54
=3 I
w i
p.
:2
f4
*
A = -0.P02:0.025
$3.. 2
* I
AA = —0.0lS:0.038

 

 

 

ANGLE

Figure C—l.

0’10" zd’ao"Ho"56’30775’803so"o'10"26’3o"Ho‘sfi's???ao‘ 30‘

ANGLE

 

 

126

Figure C—2. Gamma-ray angular distributions from the 116Sn(p,nY)116Sb
reaction at 6.25 MeV. The data are normalized to the

isotropic 93.7 keV Y ray.

INTENSITY

INTENSITY

1.1..

1.0 .

127

 

108.5 keV I

—0.017i0.115

0.076t0.168

TD #fv %

352.2 keV

   
 

O.260i0.034

0.022:0.047

 

2.2 .
2.0 .
1.8 -
1.8 -
15+ .
1.2 .

1.0 4

103.0 keV

-0.065t0.010

0.018i0.014

.D *ru »

 

A

307.8 keV

I

 

0.542t0.090

0.049i0.131

 

 

 

L l

0’10720730‘ Ho" 50°30" 73’ ao‘so"o’1o" 20‘ 30" H6“ so" so" 70" so“ so“

ANGLE

Figure C—2.

ANGLE

 

INTENSITY

INTENSITY

2.8 q
2.”! -
2.2 -
2.0 _
1.8 .
1.8 .
1H .

1.2

128

 

410.9 keV

 

455.2 keV

O.6Ali0.019

0.086i0.027

*
2
*
z.

O.300:0.066

-0.082i0.096

 

pie-i:

 

 

 

363.0 keV

 

424.2 keV

-o.287:o.027 I

0.03Si0.037

 

A =

 

-O.254i0.031

0.012i0.043

 

 

0' 10 ° 20" said“ so" so" 70‘ 807' so"o'1a'° 20" 30" HOT°SO°BOV° 7o" 80'” 30"

ANGLE

Figure C-2 continued.

ANGLE

INTENSITY

INTENSITY

129

 

 

 

 

   

 

 

 

518.0 k V 574.5 k V
1.1. e e I
1.0- I
I
.8-
.8.
I
I
.7-
3% >3:
A2 = -O.176t0.030 A2 = -O.214i0.148
* *
.8. A4 = -0.023:0.040 { A4 = 0.133:0.210
1‘1“ 480.6 keV 550.9 keV
I f
1.0.
.9.
08-1
.7. I i
it *
I A2 = -0.283t0.068 A2 = -O.l73f0.070
7': ‘l’t
8 ! A4 = -0.036t0.095 A4 = o.027:o.;)99
0°10 ° 20‘ 30° 90" so“ 30‘70" 871530’0" 10 ° 20" 30‘ Ho“ sh" 85° 70‘ so“ 90‘
ANGLE ANGLE

Figure C—2 continued.

“m5

130

Figure C-3. Gamma—ray angular distributions from the 116Sn(p,nY)ll6Sb

reaction at 6.65 MeV. The data are normalized to the

isotropic 93.7 keV Y ray.

INTENSITY

INTENSITY

131

 

 

 

1.1,.
103.0 Kev 157.2 & 157.4 keV
f

1.0 d //"—r
.8 a
.8 -1

k
.7.. A2 = -0.044f0.005 A2 = —O.214i0.034

* *

A!+ = 0.001:0.007 A4 = -0.044i0.049

92.2 k)V 108.5 k V
1.1. L e
I
1.0 .. I ,
I I i

.8 -
.8 e
.7 4
08 d ‘k *

2 -0.373t0.05& A2 = 0.013i0.030

* a
.5_‘ A4 = —0.089i0.070 A4 = 0.028i0.043

 

    

 

 

 

ANGLE

0°10 ° 20’ 30° H0“ 50°30“ 70° 80’ so

Figure C—3.

’0’ 10 ° 20’ 30'“ 40" 50° 30° 70‘ 80° 30°

ANGLE

 

INTENSITY

INTENSITY

132

 

2J1. 307.8 keV

1.8 ..

1.8 ..

I
a)
1
.b »rv »

363.0 keV

0.458t0.016

-0.032i0.022 .

-O.272t0.021

bfl-Nfl'

0.043:0.029

 

1'1“ 208.1 keV

1.0 .4

.3.

 

L

    

352.2 keV

-O.376i0.095

-0.086:0.125

 

 

—O.218i0.032

0.044t0.045

 

 

0'13’ 2?:30‘ L+0"so":.-‘.0I°70' 80'90‘0'10 '20'37’H07’50‘ 80"70' 80" so"

ANGLE

Figure C-3 continued.

ANGLE

INTENSITY

INTENSITY

133

 

 

 

 

LJ
4 404.2 keV 424.2 keV
1.0.
:8-
-8« .. *
A2 = -0.046:0.029 A2 = —0.l78:0.004
* *
A4 = -o.014:0.041 A4 = —o.001:0.005
J7.
366.8 keV 410.9 keV
~k
23* A2 = 0.563i0.011
*
2.0. A4 = 0.008t0.016
9:
A2 = —0.017:0.031
108.. it
A4 = -o.040:0.051
1J3.
1H.
11!.
1'05] '— fi—a-

 

 

 

 

 

 

v

0' 10 " 20" 30“ H0“ so“ so" 70’ 80‘ 30'0'107‘ 20" 30° 40‘ so" 807 70" 80'” 301'

ANGLE ANGLE

Figure C-3 continued.

 

INTENSITY

INTENSITY

L4

1.0

1.5

lfii

1.3

1.2

IA

1.0

.3

134

 

1 457.2 keV

q

-O.230i0.014

-0.0lOi0.020

bX—Ivfi-

 

480.6 keV

/

A

II

.b »ro »

-O.208t0.006

—0.013i0.008

 

 

‘ 455.2 kev
.4

A: = 0.255:0.023
4 *

A4 = —0.024:0.033

 

466.0 keV

O.221i0.020

=—O.171t0.030

 

 

L

 

ANGLE

0'10“ 207’ 30“ 40" 507' $5 707 80" 3010' 10 "‘ 20730“ 40’ 50“ 307’ 709' 80‘ so"

ANGLE

Figure C-3 continued.

 

 

INTENSITY

INTENSITY

135

 

 

 

 

    

 

 

 

101 .J
550.9 keV 628.7 keV
I
1.0 .. W
i
.8 .
8 *
' ‘ A2 = -O.168t0.008 A2 = -0.006t0.014
A: = 0.010t0.039 A: = -0.020i0.020
.7
1.1.
518.0 keV 574.5 keV
1.0 . I
.s I
.8.
* A
2 -O.206i0.027 A2 = -0.074i0.020
* *
'7-‘ A!4 = -0.018:0.039 A4 = 0.0SO:0.029
0' 10 ° 20' 30‘ um" 50" 80° 70' 80‘ 30’0' 10 ' 20' 30" H0" 50“ Go" 73‘ 80" 30"
ANGLE ANGLE

Figure C-3 continued.

 

INTENSITY

INTENSITY

136

 

1.1.

1.0 .

.9.

712.0 keV

 

= -O.230f0.023

= —0.037:0.033

 

 

637.9 keV

bX-NX-

778.5 keV

-0.065t0.024

-0.038i0.035

 

 

-O.420i0.021

   

-0.0l7i0.029

AA

 

ANGLE

Figure C-3 continued.

0’ 107' 20‘ 30" H0“ 507’ G0“ 70" 80" 30’0' 10 '° 20" 30" N0" 50" Go" 70‘ 80" s ’
ANGLE

 

 

 

137

Figure C-4. Gamma-ray angular distributions from the 116Sn(p,n‘Y)116Sb
reaction at 7.32 MeV. The data are normalized to the

isotropic 93.7 keV Y ray.

INTENSITY

INTENSITY

138

 

 

 

1.1
103.0 keV 157.2 & 157.4 keV
1.0 .
I
.8 d
.8 1 * 7‘6
2 = —0.03410.005 I A2 = -O.l63i0.015
A A
4 = 0.005:0.006 A4 = -0.004:0.021
.7 ..
92.2 keV 108.5 keV
1.1 ..
1.0 ..
.8 q
.8 ..
A
-O.208:0.063 A2 = -0.037:0.024
.7 . .k
= -0.045:0.079 A4 = —0.003:0.035

 

 

   

 

 

 

0' 10 ' 20" 30' 90' 50' 33' 70‘ 30‘ so'o‘ 10 " 20’ 30' 90' so" 30‘ 70780; 30'

ANGLE
Figure C-A.

ANGLE

INTENSITY

INTENSITY

139

 

1‘” ‘7 208 .1. keV
1.3 ..

1.2 .
1.1 .. f
1.0 q
.3 ..
.8 ..

‘7‘ -0.268+0.041

-0.117t0.059

>
IT

.6.

    

307.7 keV

A

I.‘ 7(- N 2(-

0.194t0.019

-0.083:0.023

 

180.9 keV

102 4
101 .1

1.0 ..

—0.100t0.034

 

-0.054:0.044

 

 

 

294.1 keV

N X-
II II

b >5-

-0.374i0.051

0.084:0.079

 

 

ANGLE

Figure C-4 continued.

0’ 10 ' 20‘ 30' 90° 50‘ Go' 70‘ 80' 30‘0' 10 ’ 20' 30" '40" 50' 3070' 30‘ 30‘

ANGLE

 

 

INTENSITY

INTENSITY

140

 

 

 

 

 

  
 

 

 

 

funny: ’1:

1-1« 352.2 keV 366.8 keV
100.1 f
.8.
9k *
‘3‘ 2 -o.182:o.016 A2 = —0.044:0.016
: = -0.008t0.022 A: = —0.037:0.021
.7.
338.]IkeV 363.0 keV
2.3.
f
2.2.
2 o I k
' ~ A2 = -0.l79:0.011
1.8. A: = —o.009:ro.014
1.6-
1.».
I
1.2. ..
A2 = 0.523i0.100
1.0. A
A4 = -O.224t0.138
.8.
I
0' 10 ' 20' 30" 90" so" 80’ 70' 30' so‘o’ 10 " 20' 30‘ 40' so" 80’ 70" so" so"
ANGLE ANGLE

Figure C—4 continued.

INTENSITY

INTENSITY

141

 

1.5. 404.2 keV 424.2 keV

0.072:0.109 A

-0.109i0.007

bX—NX-
ll

DX-NX-
ll

-0.047t0.140 A 0.002:0.008

 

p
.
H
l

H

I

.3.

T

2.1. 395.6 keV 410.9 keV

2.0 .
1.9 .
1.9. A
1.7 . A
1.6 ..
1.9 .
1.3 .
1.2 .
1.1 .

1.0 d
.3 .‘

o' 10"20" 30" I10" 50" Go" 70" 30" 90’0" 10"20" 30" no" so" so" 70" 90" 90'
ANGLE ANGLE

Figure C-4 continued.

 

 
 
 
   

-0.049:0 . 018

>
II

0.471:0.008

bfl-N)!’

0.004:0.022 0.028i0.010

9"
UI

 

 

 

 

INTENSITY

INTENSITY

142

 

 

 

 
   

 

 

 

 

 

455.2 keV 466.0 keV
* 1':
A2 = 0.166t0.017 A2 = 0.111:0.019
it 3':
La. A4 = -0.006i0.021 A4 = -0.033:0.025
1.2.
1.1.
1.0.
.3
432.6 keV 457.2 keV
2.2.
it 7’:
: + = — +
2.0.. A2 0.489_0.084 A2 0.160_0.019
A :9:
4 0.315i0.106 A4 = -0.017i0.024
1.3.
1.6.
‘1'
1.9.
102. JP
1.0.
I
L I
.8-
0'10'20'30'30'50’80’70'30'30'0'10'20'30’30'50’90’70'30’30’

ANGLE

 

Am

Figure C-4 continued.

143

 

 

    

 

 

 

 

 

 

 

 

 

 

 

1;?! 550.9 keV 590.1 keV *r
V
1F
1.1.
1.0 '
E s
3 .9.
r1
.0.
* *
A2 = -O.156t0.012 2 -0.l77t0.070
.7 >9: *
‘ A4 = 0.009i0.015 T A4 = -O.l38:0.092
.6.
480.6 keV 574.4 keV
u. I
1.0.
g .8.
E .a.
07: 7‘: *
A2 = -O.157:0.008 A2 = —O.l77:0.070
* V 3':
J3. A4 - 0.021:0.011 A4 — -0.025:0.091
Mrmdn—dh—vfir :__:_. L ‘;_ e, :; .:_ ;_.:,.<:_;:, {5‘ : :
0"10'wao‘uo'so‘co'n’eo'sa'o‘m’zo'ao'aa'so'eo'ro‘eo'so‘
AISLE A“

Figure C-4 continued.

1A4

 

628.7 keV 653.9 keV
.c 7‘:
A = 0.0 :(. r - = — . r f .
1.24 I ‘2 93 )033 A2 0 O)3 0 079
A *
A4 = 0.027i0.070 A4 = 0.157f0.102

     

I

1.1.

 

1.0 .

INTENSITY

.9.

 

 

 

621.5 keV

1.7 .
1.6 .
1.5 .
1.1! .
1.3 .
1.2 .
1.1 .
1.0 .

.9 .

.8 .

.7 .

INTENSITY

 

   
 
   

J.

\2

O.280t0.256

0.264i0.270

{

I
1}

 

1..

—0.030i0.051

0.028i0.064

11’

{I
i

 

Figure C-A continued.

.3 . . . . _ . i . . . . . . . 3 ,
0'10 ' 20’ ao’qo‘so'eo' 70’90'90‘0' 10 ' 20' 30' Ho' so’ so' 70’ 80' 30'
ANGLE

ANGLE

 

IJVTElfliITY'

INTENSITY

145

 

  
  
  

 

 
       

712.0 keV 778.5 keV
101.
9%
1.0. A2 = -0.458:o.062
i:
A4 = 0.067:0.075
.9. I I
.8.. I
J’. *
A2 = —0.2oo:0.022
k
'6‘ A4 = 0.025:0.031
:5.
705.0 keV 762.1 keV
1.3. *
A2 = —O.105:0.026
*
1.2. A4 = 0.106t0.036
101. I
1.0d I
7%
.9. A2 = 0.150t0.040
1':
A4 = 0.018:0.051
.8

 

 

 

 

0'10 ' 20' 30" Ho" 50" so" 70" 80" so'o’ 1o ' 20' 30’ «0‘56' so" 70’ 36' 90'
ANGLE ANGLE

Figure C-4 continued.

- P fiLL'F“ ' ' -
E) t .-
fl

INTENSITY

146

 

"1‘ 1055.3 keV V

 

1.0 .

 

 

-O.110:0.034

 

 

-0.047:0.045

 

 

 

O k V l
‘2. 917 7 e 1
‘k
T- A2 = -00020:00035 v
1!:
A4 = -0.059i0.047
lei-I v
0 u
u 0
1.0. ‘
‘F
.31

 

 

 

 

0'10 ' 20’ 30' «0' 50" Go' 70" 90" so'
ANGLE

Figure C-4 continued.

   

”'TIWI‘QHILTIQI‘Mfiiflrflfyiflitflflgfiflfuflmfl“