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I‘.”;- IL‘MIIM ”1:13: III" m LIEI‘II'I‘J IIL‘ THF-‘w ' ~uvh‘fi'i iIBRARy Kim, Univ crsi ty This is to certify that the thesis entitled IN-BEAM Y-RAY SPECTROSCOPY OF EXCITED STATES IN ODD-MASS N=80 NUCLEI presented by Rahmat Aryaeinejad has been accepted towards fulfillment of the requirements for Ph.D. degree in .ChemianzL Major professor Date May 13 , 1980 0-7639 l‘\\ L} I'll! ad}; "'W’w OVERDUE FINES: 25¢ per day per item RETURNING LIBRARY MTERIALS: Place in book return to remove charge from circulation records IN-BEAM.Y-RAY SPECTROSCOPY OF EXCITED STATES IN ODD-MASS Ni80 NUCLEI BY Rahmat Aryaeinejad A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Chemistry 1980 ABSTRACT IN-BEAM.Y-RAY SPECTROSCOPY 0F EXCITED STATES IN ODD-MASS n=80 NUCLEI By Rahmat Aryaeinejad The level structure of the N-80 nuclei, 1“3Eu, 1“1Pm, and 139Pr have been studied using the techniques of in-beam y-ray spectroscopy. The data were obtained by measuring y-ray singles spectra, excitation functions (in 1“3Eu case), prompt and delayed y-Y coincidences, and angular distributions of the y-rays, following the (p,2ny) and (c,4ny) reactions. In all of these experiments, high resolution Ge(Li) detectors were used. For most of the levels in these nuclei, spin and parity values could unambiguously be attributed on the basis of the angular distribution data from this work and inputs from previous B-decay data. (conversion electron data and logft values). Levels in 143Eu were populated by the 11+“Sm(p,2n.y)1"'3Eu reaction. A total of 37 y-rays deexciting from 30 states was assigned in ll”Eu. The calculations were performed to explain the resulting level structure in 1l’3Eu in terms of a triaxial weak-coupling model for both prolate and oblate deformations. These calculations indicate that 1“Eu has a slight oblate deformation. The (p,2ny) and (c,4ny) reactions were used to investigate the excited states in 1“Pm and 139Pr. The half-life of the 628.6 keV iso- meric state (ll/2-) in lule was measured to be 0.63:0.02 us. In addition, Rahmat Aryaeinejad another isomeric state was found in lkle at 2530.9 keV from (6,4ny) reaction. The accurate measurement of the half-life for this state was not possible from present work, but estimated to be more than 2 us. The resulting level structure observed in 11+le and 139Pr are explained quite satisfactorily within the limits of a triaxial weak- coupling model. Finally, a survey was made of all of the energy state systematics of the low energy levels (below 3 MeV) of odd-mass Nh80 isotones. From these observations, some predictions and suggestions for future experi- ments have been made. ACKNOWLEDGEMENTS I sincerely wish to thank Dr. Wm. C. McHarris for suggesting this region of study. His expert guidance and patience during the experi- mental work and preparation of this thesis are greatly appreciated. I also wish to thank Dr. A. Galonsky for his careful review of this thesis and his helpful suggestions. Dr. Richard B. Firestone deserves my sincerest gratitude for his never-ending words of encouragement and his special advice. I further wish to acknowledge Dr. Philip Walker for providing many useful discussions and advice during the latter part of this study. Mr. W. H. Bentley has provided stimulating discussions and advice throughout the data acquisition and analysis. Finally, I particularly wish to thank Judy Schmidt for typing the final copy of this thesis under the usual pressure of a deadline and for her editorial suggestions. ii TABLE OF CONTENTS LIST OFTABLESCOOOO....0.0.0.0..........OOIOOOOOIO...... 00000 00.... LIST OF FIGURESOOOOOOIOOOOOO......OOOOOOOOOOOOOOOOO.......OOOOOOOOO CHAPTER I. INTRODUCTION................................. ........... ..... II. THEORETICAL CONSIDERATION.................... ....... ......... 2.1. Description of the Total Hamiltonian................... 2.2. Properties of the Triaxial Core.............. ..... ..... 2.3. The Model Parameters and Their Determination ........ ... III. EXPERIMENTAL APPARATUS AND METHOD.......... ..... . ........... . 3.1. Singles Experiments.... ...... ......... ....... ..... ..... 3.2. Coincidence Experiments......... ............ ........... 3.3 Angular DiStribution Experiments ................... .... IV. CHAPTER IV................................................... 4.1. 4.2. Experimental Details and Results for the (p,2ny) Reaction............................................... 4.1.1. Target and Reaction.. ................ . ......... 4.1.2. y-Ray Singles Spectra .......... ..... ........ ... 4.1.3. Excitation Functions ............... ....... ..... 4.1.4. Coincidence Spectra...... ......... . ............ 4.1.5. y-Ray Angular Distributions ............ ........ 4.1.6. The 1“Eu Level Scheme. ..................... Triaxial Calculations and Discussion ................... 4.2.1. Single-Particle States ......................... iii 11 14 14 15 18 21 21 21 24 24 28 33 33 44 44 Page 4.2.2. Negative-Parity Collective States............... 45 4.2.3. Positive-Parity Collective States............... 48 v. 139m EXPERIMENTAL RESULTS AND DISCUSSION..................... 51 5.1. Experimental Details and Results for the (p,2ny) ReactionOOOCCC......O.........CCCCOCOOCOOOOOCC00.0.00... 51 5.1.1. Target and Reaction...... ..... .................. 51 5.1.2. y-Ray Singles Spectra ......... .................. 51 5.1.3. Coincidence Spectra............................. 52 5.1.4. y-Ray Angular Distributions..................... 57 5.2. Experimental-Details and Results for the (a,4ny) Reaction........00.........0............OCOCCCOCOCOOCOOO 60 5.2.1. Target and Reaction............................. 60 5.2.2. Y—Ray Singles Spectra........................... 62 5.2.3. Coincidence Spectra............ ..... .. ......... . 67 5.2.4. Y-Rays Angular Distributions.................... 67 5.3. Construct of the 1L’le Level Scheme and Comparison...... 70 5.3.1. Level Scheme and Spin-Parity Assignments from.(p,2nY) Reaction........................... 70 5.3.2. Level Scheme and Spin-Parity Assignments from (a,4nY) Reaction........................... 78 5.3.3. Comparison Between the (p,2nY) and (a,4ny) Reaction and with Other Experimental Results.... 85 5.4. Discussion of Level Configurations ....... ............... 88 5.4.1. Single-Quasiparticle States...... ......... ...... 88 5.4.2. Negative-Parity Collective States............... 88 5.4.3. Positive-Parity Collective States ....... ........ 89 VI. CHAPTER VI 6.1. Experimental Details and Results for the (p,2ny) Reactions......................... ........ ...... ........ 91 Page 6.1.1. Target and Reaction............................. 91 6.1.2. y-Ray Singles Spectra........................... 92 6.1.3. Coincidence Spectra..................... ........ 92 6.1.4.. y-Ray Angular Distributions..................... 97 6.2. Experimental Details and Results for (a,4ny) Reaction...101 6.2.1. Target and Reaction.............................10l 6.2.2. y-Ray Singles Spectra ....... ........ ...... ......101 6.2.3. Coincidence Spectra............ ..... . ..... ......103 6.2.4. y-Rays Angular Distributions....................108 6.3. Construct of the 1”Pt Level Scheme and Comparison......113 6.3.1. Level Scheme and Spin-Parity Assignments from.(p,2ny) Reaction...........................113 6.3.2. Level Scheme and Spin-Parity Assignment for (a,4ny) Reaction............................1l9 6.3.3. Comparison Between the (p,2nY) and (c,4nY) Reaction and with Other Experimental Results....122 6.4. Discussion of Level Configurations.... ..... .... ....... ..122 6.4.1. Single-Quasiparticle States............. ..... ...122 6.4.2. Negative-Parity Collective States........ ....... 125 6.4.3. Positive—Parity Collective States........ ...... .126 VII.. SYSTEMATICS OF THE ODD-MASS N‘8O NUCLEI.......................128 VIII. SUMMARY AND CONCLUSIONS ..................... ..................132 BIBLIOGRAPHY........ ........ . ............. ... ...... .................134 APPENDICES.................. ......... ................ ............. ..138 A. Gated Coincidence Spectra of Transitions in M3Eu.........138 B. Angular Distribution Plots of 1“3Eu Transitions.... ....... 144 C. Gated Coincidence Spectra of Transitions in 1“Pm from (p,2ny) Reaction.. ........... .............. ....... ...149 V Page Angular Distribution Plots of 1“Pm Transitions from (p’an) Reaction..ooooooooooooooooooooooooo0000000000154 Gated Coincidence Spectra of Transitions in lulpm from (6,4217) Reactions...oooooooooooooooo00000000000161 Angular Distribution Plots of 1“Pm Transitions from (a,4ny) Reaction.....................................l67 Gated CoincidenCe Spectra of Transitions in 139Pr from (p’an) Reaction.....COO0.000000000000000.0.0.0.0....173 Angular Distribution Plots of 139Pr Transitions from (p,2nY) Reaction.....COOOOOOOOOO......OOOOO0.00.00.00179 Gated Coincidence Spectra of Transitions in 139Pr from (a,4ny) Reaction...............................185 Angular Distribution Plots of 139Pr Transitions from (c,4ny) Reaction.....................................206 vi 5-2. 5-3. ' 5-4. LIST OF TABLES Page Energies, relative intensities, angular distribution coefficients, and multipolarities for Y transitions in 1"’3Eu from (p,2nY) reactions.......................... 26 Summary of coincidence results for the 11mSm(p,2ny) luSEu reaction.000000ooooooooooooooooooooooooooooonoooooo 31 Energies, relative intensities, angular distribution coefficients, and multipolarities for Y transitions in lule from (p,2nY) reactions.......................... 55 Summary of coincidence results for the 11+2Nd(p,2.nY) lulpm reactionoooooooooooooooooooooooooooooooooooggg..... 58 Energies, relative intensities, angular distribution coefficients, and multipolarities for Y transitions in 1“Pm from (a,4nY) reactions................... ....... 65 Summary of coincidence results for the 11‘lPr(czt,4nY) 1‘.le reactionOOOOOOOCOOOO......OOOOCOIOOOOO0.0.0.0000... 68 Energies, relative intensities, angular distribution coefficients, and multipolarities for Y transitions in 139?: from (p,2nY) reactions.......................... 94 Summary of coincidence results for the 1"‘°Ce(p,2nY) 139Pr reaction.00coo.oooooooooooooooooooooooo000000000ooo 99 Energies, relative intensities, angular distribution coefficients, and multipolarities for Y transitions in139Pr from (“,4nY) reaCtions‘0.0000000000000000so ooooo 105 Summary of coincidence results for the 139La(a,4nY) 139Pr reaction0000000000.0.0.0...00...... ..... 00.0.0.0...110 vii 4-2. 4-3. LIST OF FIGURES Page Vector diagram of a particle coupled to a rotating core.O....00.0.0000.........IOOICOOOOOOIOOOOO......OOOOOOOOO 5 Irrotational moments of inertia as functions of Y........... 8 Low-energy spectrum of an even triaxial core as a 10 f‘mction Of YOOOOOOOOOOOOOOOO0............OOOOOIOOOOOOOOOOOO "FAST-SLOW" coincidence diagram............................. 16 The goniometer facility, showing the activation chamber and detector mounting............................... 19 Excitation functions calculated by the evaporation code ALICE for p's on a 1"”‘Sm target. Note that there are two curves for each of the Pm isotopes, one for the evaporation of an a particle, the other for evaporation of 2n + 2p.................................. 22. In-beam singles Y-ray spectrum.from the reaction, 1““Sm(p,2ny)1“3su, taken with the Ioz-effieient Ge(Li) detector placed at 125°.............................. 25. Excitation functions for seven of the more prominent lusEuYraYSOCOOOOOOOOOOOOOOO......OOOOOOOOOOOOOOOOOO ....... 29 In-beam Y-Y coincidence spectra for the reaction, 1MSme,2nY)1‘*3Eu. The integral coincidence spectrum ("all events") is shown at the top, and three repre- sentative smoothed gated spectra are shown underneath....... 30 Four representative angular distributions of 1“3Eu Y rays, together with their fits calculated by the code GADFIT. The points correspond to 90° and the backward angles, 100°, 110°, 125°, 140°, and 155°........... 34 1‘”En level scheme as determined by the 1‘*“Sm(p,zny) 1“3Eu reaction. The asterisks before " assignments indicate that we relied heavily on the 1“3GdM*9 B+/8 decay [F178] for these assignments. Also the dashed Y transitions are weak transitions seen in i"‘3Gd”""57 decay but not seen in our in-beam studies; however, they originate from levels seen in the in-beam studies. It should be noted that there are two 1059.3-keV tran- sitions in this level scheme................................ 36 viii 4-9. 5-1. 5-9. Page Decay schemes of lkacdg and 1“3de from Ref. [F178] for comparison with our in-beam studies.............. 37 Energies of calculated excited negative-parity states in ll*3Eu compared with our experimental findings. We calculated these energies using a triaxial weakrcoupling model, coupling the Uh11/2 state to a deformed core. Results for both prolate and two different oblate deforma- tions are shown; a slight oblate deformation seems indicated. Spins are shown in 2J..................... 47 Energies of calculated excited positive-parity states in 1“Eu compared with our experimental findings. We calculated these energies using a triaxial weakrcoupling model, coupling both the Udslz and Ug7/2'1 states to an oblately deformed core. Spins are shown in 2 ................................ 49 Y-ray singles spectrum of 142Nd(p,2nY)1“1Pm taken with the l7Z-efficient Ge(Li) detector placed at 1250.00.0000......OOOOOOOOIOO...O0.00.00.00.00.0.0.0.0000... 53 A detector efficiency curve for a l7Z-efficient Ge(Li) detector with a source detector distance of 20 cm.................................................... 54 Excitation functions for 1"’1Pr(oi,:m) reactions, calculated using the code CSBN.............................. 61 Y-ray singles spectrum of 1HPr(c,4nY)1“1Pm taken with 7.7Z-efficient Ge(Li) detector placed at 1250......0............‘C..................‘O..... 63 A detector efficiency curve for a 7.7Z-efficient Ge(Li) detector with a source detector distance Of 20 cmOOOOCO.....OOOIOOOO.......OOOOOOOOOOOOOOOOIOO ....... 64 Level scheme of 1“Pm obtained from (p,2nY) reactionCCOO......O....I....OOOOOOOOO......OOOOOOOOOOOOOOOOO 71 Level scheme of 1“Pm obtained from (a,4nY) reaction............OOOOOOOIOOOO......OOOOOOO ............... 79 Delayed coincidence spectrum. This spectrum enhances those transitions that feed directly or indirectly into the 628.6-keV state (t1/2 8 0.63 usec) in lule.......... ....................... 81 Time axis projection on a semi-logarithmic plot illustrating the half-life of 628.6-keV 82 state in 11+le0000000000000 ......... ...... .......... O ..... .0 ix Figure 5-10 0 6-3. 6-4. 6-5. 7-1. Page Energy levels of 1HPm. Levels in columns 1 and 2 are from present work.while levels in column 3 are from B-decay. Spins are shown in 2J................................................. 86 Y-ray singles spectrum of 1°°Ce(p,2nY)1“1Pm taken with the l7Z-efficient Ge(Li) detector placed at 1250......OI.........CCOOOOOOOOIOOOOO ..... 00...... 93 Delayed coincidence spectrum. This spectrum enhances those transitions that feed into the 822. O-keV state (t1/21= 36 nsec) and 113. 9-keV (cl/2 s 2. 6 nsec) in139Pr from.(p,2nY) reaction............ 98 Y-ray singles spectrum of 139La(a,4nY)139Pr taken with 7.7Z-efficient Ge(Li) detector placed at 12500.00.........OOOOOOOOOOOOOOO0.0.0.0000...00.00.000.00102 Low energy Y-ray singles spectrum of 139La (a,4nY)1 Pr taken with a small volume planar Ge(Li) detector placed at 90°...............................104 Delayed coincidence spectrum. This spectrum enhances those transitions that feed into 822.0-keV state (t1/2 = 36 nsec) in 139Pr from (a,4nY) reaction......................................JD9 Level scheme of 139Pr obtained from (p,2ny) reaction.......00.00..........OOIOOOOOOOC00.0.0000... ..... .0114 Level scheme of 139Pr obtained from (a,4nY) reactionOOOCOOO0.00.00.00.00.........OOOOOOOOOOOOO ..... 0.0.0120 Energy levels of 139Pr. Levels in columns 1 and 2 are from present work while levels in column 3 are from B—decay [Be69, Bu71] and levels in column 4 are from scattering reaction [Go72]. Spins are shown in 2J..... ........ .......123 The position of known states in3 odd-mass N=80 isotones. The data for 1331,15Cs, and 137La are from B-decay or a combination1 of B-decay and in-beam studies. The13Pr, “Pm, and M3Eu data are1 from the present in-beam study. The states in 39Pr above 3 MeV from (a, 4ny) reaction are not shown in this figure. Also, spins are shown in 2J....................... ............. ..129 Gated spectra of transitions in M3Eu from (p,2ny) reaction. Background subtraction using the adjacent continuum has been Figure Page included. The spectra are arranged according to increasmg energy...O.....IOOOOOOOOOOOIOOO...0........0.0138 Angular distribution plots of ll’3Eu transitions obtained from.(P,2ny) reaction. The data were tam in the 90-180. quadrant...0.006.000.0000...00000000000144 Integral coincidence and gated spectra of transitions in lule from (p,2ny) reaction. Background subtraction using the adjacent continuum has been included. The spectra are arranged according to increasing energy.....................149 Angular distribution plots of 1“Pm transi- tions obtained from (p,2ny) reaction. The data were taken in the 90-180° quadrant.....................154 Integral coincidence and gated spectra of transitions in lule from (a,4ny) reaction. Background subtraction using the adjacent continuum has been included. The spectra are arranged according to increasing energy.................161 Angular distribution plots of 11+1Pm transi- tions obtained from (a,4ny) reaction. The data were taken in the 90-180° quadrant.....................167 Integral coincidence and gated spectra of transitions in 139Pr from (p,2ny) reaction. Background subtraction using the adjacent continuum has been included. The spectra are arranged according to increasing energy.................173 Angular distribution plots of 139Pr transi- tions obtained from (p,2nY) reaction. The data were taken in the 90-180° quadrant.... ...... ...........l79 Y-integral coincidence and Y-gated spectra (identifying high energy coincidences) of transitions in 39Pr from (a,4ny) reaction. Background subtraction using the adjacent continuum has been included. The spectra are arranged according to increasing energy.....................135 X-integral coincidence and Xrgated spectra (identifying low energy coincidences) of transitions in 139Pr from (0,4n7) reaction. Background subtraction using the adjacent continuum has been included. The spectra are arranged according to increasing energy......... ...... ......197 xi Figure Page J. Angular distribution plots of 139Pr transi- tions obtained from (a,4ny) reaction. The data were taken in the 90-180° quadrant....................206 xii CHAPTER I INTRODUCTION One of the more interesting regions of the nuclidic chart for cur- rent study is the region immediately below the Nh82 closed shell. Here long chains of isotones are amenable for study, encompassing both neutron- excess and neutron-deficient nuclei; a wealth of Nd and other isomers is available; and a large number of targets is available for cross-compari- son in various in-beam experiments. The neutron—deficient Nh80 isotones are among the most interesting of these nuclei because, although they lie close to the major closed shell, they lie at a considerable distance from stability. Thus, they are transitional nuclei: They contain many well- defined shell-model states, but they lie near the edge of the onset of deformation, so many of their higher-lying states can be characterized not only as multiple particle states, but also as (deformed) collective states. Also, the juxtaposition of the h11/2 shell-model state with various low-spin states leads to a wealth of both high- and low-spin states in these nuclei. The level structures 0f l”Eu, lgle, and 139Pr have been investigated in this thesis, using the techniques of in-beam y-ray spectroscopy. Levels in 1“3Eu were populated by the (p,2ny) reaction only, whereas levels in l“Pmand 139Pr were populated by both (p,2ny) and (a,4ny) reactions. These supplement and complement other previous studies of states in these same nuclides excited by B+/€ decay. The in-beam experi- ments also tended to excite higher-spin states than those known from existing B-decay data. High-resolution single y-ray spectra, excitation functions for the various y-rays (only in the case of ll*3Eu), prompt and delayed y-Y coinci- dences and angular distributions of the y-rays in these nuclei were measured in an effort to elucidate their level schemes in as much detail as possible. This information would be of great value for the testing of existing nuclear models which could describe the resulting level structure of these nuclei. Generally, because of the weak deformation of the nuclei in this region, weakrcoupling features of the level schemes are expected. In the case of 1“Eu, calculations were performed to explain the resulting level structure in terms of a triaxial weak-coupling model for both prolate and oblate deformations. These calculations indicate that lusEu has a slight oblate deformation. The structure of the thesis will be divided into eight chapters: Chapter II discusses the theory of triaxial weak-coupling model, used in this study. Chapter III describes the many types of experimental set—ups used during the course of present investigations. Chapter IV describes the experimental and theoretical results of 1“Eu obtained from the (p,2ny) reaction. Chapters V and VI describe the experimental results of ll+1Pm and 139Pr, respectively, obtained from both (p,2ny) and (a,4ny) reactions. In Chapter VII , the systematic behavior of some of the nuclear pro- perties in the odd-mass Nh80 region are discussed. Finally, the summary and conclusion will be found in Chapter VIII. CHAPTER II THEORETICAL CONSIDERATION Since the collective model works so well for even-even nuclei in many regions of the periodic table, it is natural to attempt to extend it to odd-mass nuclei in these regions. If the properties of the even- mass isotopes are well explained by collective motions of all the parti- cles, one would expect that the addition of an extra particle should Shani to a behavior resembling that of the even-mass core but modified by the presence of the extra particle. Some of the publications [He62] used an adiabatic approximation which considers the odd nucleon to be in a definite single-particle state. This approximation is certainly inadequate for weakly deformed nuclei, where the odd nucleon is coupled to the intrinsic shape. Pash- kevich and Sardarian [Pa65] were the first to perform the calculation preposing that the model contains the weak-coupling limits as well as the strong-coupling limit and also could describe the various interme- diate regions. The model investigated in this study consists of an odd nucleon coupled to a rotating triaxial core. The odd nucleon is considered as a quasiparticle that represents either a particle or a hole or a super- position of both. For the most part the summary of the particle or hole- core coupling treatment follows a more detailed presentation of Meyer-ter- Vehn [Me75]. 4 2.1. Description of the Total Hamiltonian The angular momentum of odd—A deformed nuclei is due both to the rotational angular momentum of the core (or whole) and to the angular momentum of the odd nucleon. Figure 2-1 shows a vector diagram of an odd-A deformed nucleus consisting of a single particle coupled to a rotating core. According to this figure, a rotor with angular momentum R, representing the core of the nucleus, is coupled to the angular momen- tum 3 of a single particle to form a total angular momentum I} The total angular momentum I has the component M along the fixed axis Z and the component K along the nuclear symmetry axis 3. The projection of j'on the nuclear symmetry 3-axis is O. In the axially-symmetric case, the core angular momentum R is perpendicular to the 3-axis, and the total angular momentum I has a projection K equal to O. In a rotating system like this, the total Hamiltonian can be written: H - HR'+ HP (1) where HR and HP are the rotational and particle Hamiltonians , respectively. The rotational Hamiltonian may be written: ‘2 2 if. 14.4-1-1}. '1 +j_I,) I and j are in different frames, so a (+) operator in one acts like a (-) operator in the other with the notation of I1 = I1 i 112 and ji - j1 i ijz. The first term depends only on the total angular momentum and is a con- stant of the motion. The second term represents a recoil energy of the rotor and depends only on the intrinsic variables (including the spin variables a, j, and K). The third term is an effect of the Coriolis force on the particle in the rotating coordinate system and will be given the name "rotation—particle coupling." The total Hamiltonian is invariant .ouou wswumuou m ou omaasoo mapauuma m «0 Bahamas uouom> .HtN shaman under 180° rotations about the intrinsic axes (D2 Symmetry group). These symmetries allow the wave function to be written in the form 2 an... - VZT—‘g‘ g C‘x’a£"’(DS?xxg.’+(-)"""Dfi’-:x‘-’}a.). <3) I, .t where summation is restricted to IKI~$ I , IQI < j, (K + j) even, (9 + 1) even, and T - i1; Déi) guishes between particle and hole states, and a labels all states for a denote rotational D-functions. The index I distin- certain total angular momentum I. In this case, the energy can be simply diagonalized [HerSO] and the various limits considered afterwards. The energy levels of the axially symmetric are characterized by a single par- ticle energy and a set of rotational levels built upon the single particle state. The expression has been shown to be: . l EK(’) = E;’+B%,:l(l+ ‘)+ 5K,.,,a(—')l+ "(I+'§)}o (4) where the parameter Eél) and the decoupling parameter a depend 'in some way on the nucleon configuration, and where Eép), a 0th order energy (an "ideal" energy before the Perturbations set in) is conventionally chosen so that EK(I) will have the experimental energy. The second term in the braces, a so-called decoupling parameter, is actually a special case of the Coriolis shift operator. When K a 1/2, the wave function, symme- tized with respect to iK has a K a +l/2 and a K = -l/2 portion. These can be connected by the 1:1? shift operator. For this special case then, ““3 halves of the wave function get scrambled among themselves. In other places simply connects K and K i 1 if the states lie close by. Itj¥ The numerical solution of the energy spectrum of an odd nucleon coupled to a triaxial rotating core has been calculated as a function of the deformation 8, the asymmetry y, and the Fermi energy Af by Meyer-ter- Vehn [Me75]. The spectroscopic quadrupole moments and the magnetic moment can be written as: Qsz"-(_f (2, f)<1anQuIa>. (5) ”In a 981+ (_: (15 ;) (IGHMHId>, (6) and for the reduced 32 and M1 transition probabilities 3052; Ian —. m - i—nKI'a’HQHIaN’KZIH)’ (7) B(Ml;1¢ -* I'a') - |(1'¢'HM||1¢>IZI(21+1)- (8) Mixing ratios are defined as: _, _ s _<_____I'a'nQuIa> ‘60“ I“ ) J0” E’Vlsn (I'a'llMllIa) (9) where EY a (BI - E1») is the transition energy in MeV. The above expressions correspond to particles coupled to the rotor; the results for holes are obtained by applying the particle-hole transformations, which reverse the sign of Q(3P) and 6, but leave all other quantities unchanged (except for quasi-particles which are particle/hole combinations having all the B's reduced). 2.2. Properties of the Triaxial Core The three moments of inertia can be written as: J, = Jog-sin: (7-%mc), K =1.2.3. (10) These moments of inertia are shown as function of Y in Figure 2.2 and the corresponding lowest states of the triaxial even rotor are given in MSUX-BO-ZOB Prolote Oblote 0° 30° 60° Figure 2-2. Irrotational moments of inertia as function of y. 9 Figure 2-3. Besides the ground state rotational band, a second 2+ state and other additional states are seen to come down in energy as a function of Y. marking the triaxial region. The energies of the first and second 2+ states have been expressed analytically by Davydov et al. [Da58] as: g 93FJ81-723in’ (37) ‘. " . ll 1 ” 2.1, 4sin’(37) ( ) and the transition probabilities to the ground state as: Isa-:2; 2:.»o*)-—Q:— 10D: 3 ”2““ (3———-’—) (12) #9— 85in (3y where the upper sign refers to the 2? state and lower sign to the 2: state. A general analytical solution for the even triaxial rotor at Y - 30° has been given by Meyer-ter-Vehn [Me75]. Since two moments of inertia are equal& :33 at y =- 30°, as seen in Figure 2-2, the Hamiltonian becomes axially symmetric about the l-axis for y = 30° and can be written as h. = aERf+4(R§+R§)]. (13) with a = 3fl2/8¢,. Due to the symmetry, the angular momentum i has a sharp projection a on the l-axis, a has to be an even integer. The energy spectrum is obtained as: E... = a[a=+4’-' \>\ ‘\‘~ 55:. /' l!’} o \ " ’4'- U? E -./\;\>\\//‘\4;2// [I 6 NF 40 - \\ ’ I V \\ ///I \ '* I. \\_\~‘~§%l"/' I, (*4- .I u zo/c ./ \ . 2 + _. 2. Figure 2-3. Low-energy spectrum of an even triaxial core as a function of y. 11 In connection with the low-excited odd-A spectrum, one is interested in the lowest states of the core spectrum, in particular, in the first and second 2+ state. 2.3. The Model Parameters and Their Determination The free parameters of the model are 8, Y, and Af. For a particular odd-A nucleus, 8 and y will be determined from the lowest excited states of the adjacent even nuclei, and A will be determined from the Nilsson 1" level scheme. All other parameters are chosen as a smooth function of the mass A; e.g. k.and A, or as a function of B and A, e.g.ét . k - f drr*(f(r))’k(r) = 206/A*(MeV). (16) 0 consistent with the splitting of the hll/z shell in the Nilsson level scheme. The inertia parameter 5% is determined by the relation, #12}, - 204/5247" (MeV) (17) The pairing energy is chosen as: A a 135/A (MeV) (18) consistent with odd-even mass difference in the mass region lOO‘=A‘=200. The procedure to determine 8, Y, and if is ambiguous for several reasons: i) The low-energy spectra of even transitional nuclei differ in general from those of a perfect triaxial rotor, and there are different ways to adjust B and y. ii) In a number of cases, the first excited energies of the even nuclei are rapidly changing with mass number so that the question arises which of the two neighbors or which average of them should be taken. 12 iii) Furthermore, there is evidence in some cases that the odd nucleon polarixes the core so that the parameters of the even neighbors are not quite applicable to the odd-A nucleus. The parameter Y can be determined from the energy ratio of the second 2+ state to the first 2+ state, by using equation (11). For particle spectra (if below j-shell), the (A-l) neighbor is chosen as reference nucleus and, for hole spectra (if above the j-shell), the (A + l) neighbor is chosen. Since the energy spectrum of the even triaxial rotor is symmetric about Y - 30° (see Figure 2-3), this procedure cannot distinguish between prolate triaxial shapes 0° < Y < 30° and oblate triaxial shapes 30° < Y < 60°. The information to which side a certain nucleus belongs has to be taken from the odd-A spectrum. The parameter 8 is determined by average,E2+ a [E2+(A‘1) + E2+(A+l)]/2. of the first 2+ energies of the (A-1) and the (A+l) neighbor, and using the equation, 1224 1/2 A7/3 22+ x (Y)] . (19) where §2+ is taken in MeV, and the y-dependent factor is equal to: Asin2(3Y) , (20) x(Y) = 9-[81-7251n2(3Y)]1/2 The position of the Fermi energy Af relative to the j-shell on which the unique parity states are built determines the particle or the hole character of the system. For a given j-shell, Af is estimated from a Nilsson level scheme for Y = 0°. This estimate is sufficient as long as A is located outside the j-shell level scheme. In cases where Af pene- trates the j-shell appreciably, the fine adjustment of if has been 13 performed by fitting approximately the first (j - 1) state of the odd-A spectrum. In this work, A is given in the form if . (Af~61)/(€2-el) f for particle spectra and if - (6(j+1/2)-Af)/(e ) for hole (j+1/2)-e(j-1/2) spectra,where ev with v a l, 2,.....j + 1/2 are the single-particle energies of the j-shell. The computer program TRIAX, which was the modified program used by Meyer-ter-Vehn at Lawrence Berkeley Laboratory, was used for numerical calculations. This program calculates energies, wavefunctions, moments, and transition probabilities of the triaxial-rotor-plus-quasiparticle model. CHAPTER III EXPERIMENTAL APPARATUS AND METHOD To arrive at the.inebeam.level scheme constructed during this inves- tigation, both standard and new techniques of y-ray spectroscopy were used. This chapter describes in a general way the apparatus in current use at Michigan State University for Y-ray measurement. It has.been divided into three sections in order to explain some significant general charac- teristics of the Y-ray spectrometers employed in this study for 1) singles, 2) coincidence, and 3) angular distribution experiments. 3.1. Singles Experiments The basic components of the singles Y-ray spectrometer used in the present study were: a) a Ge(Li) detector cooled to liquid nitrogen temperature (77°K), b) a room temperature PET (field-effect transistor) preamplifier and bias supply, c) a pulse shaping amplifier with pole-zero compensation, d) an analog-to-digital converter (ADC) or multi-channel' analyzer (MCA), and e) a data-readout system. The data analysis in the present study was carried out on the Michi- gan State University Heavy Ion Laboratory's XDS Sigma-7 computer. Peak centroids and areas were determined off line by the peak-fitting code SAMPO [R069], which was especially useful in stripping unresolved multi- plets. Gamma-ray energy measurements were made by first computing least squares quadratic calibration equations from centroid channel numbers of well-known standard energies and then computing the energies of "unknown" 14 15 Y-rays from their measured centroids. Gamma-ray.re1ative intensities were established with the aid of a detector efficienCy versus photon energy curve for energies ranging from 30.keV to 23MeV. 3.2. Coincidence Experiments Coincidence spectra have played an important role in the present research. Since the vast majority of nuclear excited states have very short half-lives as compared with our ability to measure them, coinci- dence units with resolving times on the order of nano-seconds can be used to study those transitions which are in fast or "prompt" coincidence with one another. In this manner, coincidence spectra are a useful tool for determining the relationships of the observed Y transitions. By considering energy sums, relative intensities, excitation functions, and angular distribution functions, along with coincidence relationships among the various Y-rays, it was usually possible to construct a unique level scheme. The most important and most extensive type of experimental data which were taken for this study consisted of three-parameter (EY x BY x t) coincidences. In such an experiment, two detectors were placed about 5 cm from.the target at 180° with respect to each other. Gates could be set not only on gamma peaks, but also on any desired time intervals.' Consequently, various half-lives could be determined and used efficiently in searching for unknown transitions or isomers. A block diagram of the electronics set-up for the 3-dimentional coincidence experiments is shown in Figure 3-1. The Y-rays in a true coincidence event have a distinct relationship in time, which enables us to distinguish them from random chance coincidences.‘ The necessary time 16 Source ‘Ge(Li) 2 fi Ge(Li) ' DeieftoHDeiezcior iPreomoE r—JT near 1 l T. F. A] [I'. RAJ r“—J—IlLineor U.Arnp p. l _ Delay , [ [ct-7m. [:Ac §Hcfitol __ Timing .' Timing S C A ' ' SC A - F f , - 680 . Generator 2 2 [ Delay A 2 :3 3 + a _ i i i i v i U U“ U [X-ADC W-ADC Y-ADC J w Even? x Y Event Event [W Figure 3—1. "FAST-SLOW" coincidence diagram. l7 selection can be accomplished by using a time-to—pulse-height converter (TAC). In order to measure elapsed time precisely, the TAC.require8 input pulses that provide accurate information concerning the time at which a particular nuclear event occurred. The spectroscopic amplifier distorts the shape of pulses from the preamp, decreasing rather than enhancing the steepness of the risetime of an incoming pulse.‘ This in turn makes accurate timing measurements more difficult. For this reason, our timing signals are derived from the preamp pulses before they are passed through the spectroscopic amplifier. As the preamp pulses still need amplification, they are sent through a timing filter amplifier (TFA). It is found that the time for a peak to reach a set fraction of its maximum value is almost time-invariant. The constant fraction timing discriminator (CFTD) makes use of this invariance by setting an effective triggering threshhold at a fraction of the full height of the input pulse. In order to generate the prOper pulse shape for this type of triggering, the input is branched into two paths. In one leg of the system, the input is attenuated to a fraction of its original height. In the other path the pulse is inverted and delayed by a time interval known as the shaping delay. Both signals are then added together to form a signal with a zero crossing. The constant fraction timing discriminator then uses a zero crossing discriminator to generate a logic pulse which is suitable for input into the TAC. The fast timing network generates the needed logic inputs for the TAC, but it also has a tendency to trigger on noise. This can prove to be a real problem if the energy range of pulses to be studied includes low energies. To eliminate these pseudocoincidences we make use of the ("slow") coincidence module. The slow timing network uses logic pulses generated from the energy signals (after amplification, 18 shaping and passing through a timing single Channel analyzer [TSCA]) and from the corresponding TAC.pulse to determine if a pair of Y—rays forms a true coincidence event. Then, for each true coincidence event, the slow timing opens a gate to the ABC's, allowing the TAC output and the y-ray energy signals to be analyzed and then collected on magnetic tape under a computer program called IIEVENT [Au72]. By sorting the Y-rays into= sequential time intervals, the prompt as well as the delayed Y-rays could be studied with chance or random background subtracted. The data recorded on tape are recovered later, off-line, using a program called KKRECOVERY [KKREC]. The Sorting process takes about 30 minutes per tape (3 million events) on the XDS Sigma-7 computer, and up to 120 spectra (2048—channel) can be generated in the sorting process. 3.3. Angular Distribution Experiments ' One can obtain additional information about energy levels, spins, and transition multipolarities by measuring the angular distribution of Y-rays emitted from aligned states formed by nuclear reactions. When the incoming particles impinge upon the target nuclei with velocity i, they align the nuclei such that the angular momentum vectors (f'x m?) are all predominantly in a plane perpendicular to the beam. As these nuclei decay by emitting electromagnetic radiation, they lose some of the original alignment with each transition. Although the mixing ratio of dipole and quadrupole radiation cannot be very precisely determined using these distributions, the qualitative information contained in the shapes of the curves can be helpful in confirming placement of Y-rays in the level scheme. Figure 3-2 shows a portion of the goniometer chamber in one of its many experimental configurations, here used for angular distribution l9 .wcwuczoe pompouop use possess :oHu:>fiuum Al 039533 ecu mafiZosm .zuwafiomw nouoECHcow use .Nln 4 il‘qllll . ., a, mo :38 _ .\ oczwwm .i.§ 20 . experiments in this study (The goniometer facility provides a number of other conveniences that are useful for Y-ray spectroscopy experiments). A large arm extends to both sides of the unit and provides a mounting for one or more detector packages (cryostat, dewar, preamp, etc.). This arm rotates about the vertical axis of the main body and is controlled either by the local control box or a remote control panel. The targets are held in a vertical ladder arrangement in the center of the chamber. Three 2.5- x 5.0-cm target frames can be mounted in this holder. Vertical movement of the ladder for target selection, as well as rotation of the target plane with respect to the beam, can be controlled remotely or locally. Dead-time and amplifier pileup corrections, as well as run-to-run normalizations, were made by using the digitized output from a beam current integrator to trigger a Berkley Nucleonics Corporation model No. BH-l tail-pulse generator. The pulser was in turn connected to the test input of both the angular distribution and the monitor detectors' preampli- fiers. The resulting pulser peak in the y-ray spectrum was placed so as not to interfere with y-ray peaks. CHAPTER IV 1“3Eu EXPERIMENTAL AND THEORETICAL RESULTS The 1“3de+g B-decay has been used previously to study the excited states in 11+3Eu [Va73, W176, F178]. The 1""“Sm(p,2n'y)”31m reaction was used for this study in order to populate many high-spin states not populated by the B-decay. Many experi- ments such as Y-Y coincidences, excitation functions for the various Y-rays, and angular distributions were carried out in order to construct the level scheme. In the last sections, a triaxial weak-coupling model is used to explain the experimental level scheme. 4.1. Experimental Details and Results for the (p,2nY) Reaction 4.1.1. Target and Reaction The states in 143Eu were excited by the 1"‘L‘Sm(p,2nY)1‘*3Eu reaction using a 30-MeV p beam from the MSU (SO-MeV) sector-focused cyclotron. The target was prepared by vaporizing Sm enriched to 95.10% 1MSm (obtained from Oak Ridge National Laboratory) onto a thin C backing. The target was 200-300 pg/cm2 thick and the C backing 25 ug/cm2 thick. Excitation functions calculated by the compound-nucleus evaporation code [ALICE] are shown in Figure 4-1. From these it can be seen that the primary contaminants produced directly by the 30-MeV p beam were ll”‘Eu, 1“Sm, and to a lesser extent, 1“2Eu. Their decays also produced readily identifiable Y rays from states in 1“Sm, 1"‘3Stn, ll+3Pm, 1“28m, and lksz. These predictions were observed in the experiments and accounted for. 21 22 Figure 4-1. Excitation functions calculated by the evapora- tion code ALICE for p's on a 11+"Sm target. Note that there are two curves for each of the Pm isotopes, one for the evaporation of an a particle, the other for evaporation of 2n + 2p. 23 HSUX-OO-OC. p+|445m ("5Eu; total) I II m~\ oncoooooooooo\v\oloioll :———-P_ b IOOOO . o o m 3.5 cozmom- mmoco 3O 4O 50 60 70 Energy(MeV) 20 IO 24 4.1.2. Y—Ray Singles Spectra The 1“Eu singles Y-ray spectra were taken with a loz-efficient (with respect to a 7.6 x 7.6-cm NaI(T£) detector for the 60Co 1332.513- keV peak; source-to-detector distance, 25 cm) Ge(Li) detector having a resolution of 2.4 keV FWHM (for the 60Co 1332.513-keV peak). They were normally taken at an angle of 125° from the beam direction [to minimize angular distribution effects, 125° being a zero of P2(cose)]. Typically, a beam current of ~2 nA was used and the detector was placed 20 cm from the target, resulting in a count rate of ~6000-7000 cps. A singles Y—ray spectrum taken over a 2.5-h period is shown in Figure 4-2. A total of 37 Y-rays was assigned to 11”flu on the basis of singles spectra and the excitation and coincidence experiments discussed below. These are listed in Table 4-1 together with their relative intensities; also, Table 4-1 includes angular distribution coefficients and conversion coefficients which will be discussed later. The energy calibrations were performed by counting simultaneously with 60Co, 226Ra, and 116Ho‘11 radio- active sources and also using some ll’3Eu Y rays already characterized from l"30d B+/e decay [F178] as secondary standards. The errors quoted for the energies include estimated errors in the standards and are based primarily on the reproducibility of a peak and its height above back- ground. Where the energies were known more precisely from 1l+3Gd decay, these values were adopted. The errors on the intensities are based pri- marily on the reproducibility of a given peak. 4.1.3. Excitation Functions The y-ray excitation functions were obtained with p beams having energies of 30, 35, and 40 MeV. The Y rays were detected with the 10%- efficient Ge(Li) at ~90° from the beam direction and 5 cm from the target. 25 ISUI-OO-OQQ 6 Io .- O. 1 a g E". o a a a a, I .- Z: 8 s ‘JIO h Io‘ '05. .. (D I'- Z 3 <3 0 2000 2500 CHANNEL NUMBER Figure 4—2. In-beam singles Y-ray spectrum from the reaction 1L"*Sm(p,2nY)“*3Eu. taken with the lOZ-efficient Ge(Li) detector placed at 125°. 26 Table 4-1. Energies, relative intensities, angular distribution coeffi- cients, and multipolarities for Y transitions in ll*3Eu from (p.2nY) reactions. Relative Angular Distribution Energy Intensity Coefficients Miultipolaritya E:Y IY AZ/Ao Ak/Ao (keV) 117.57:o.05b 3.7 :0.2 isotropic --- M2 131.1 i0.lb 0.30:0.08 0.10:0.03 -- --- 204.7710.05b 5.0 10.4 isotropic --- -- 210.9 10.1b 1.1 i0.3 -o.55:0.12 --- M1 248.4 10.1 1.6 10.2 -0.39eo.10 0.15:0.10 -- 258.8 io.1 7.7 io.5 --- -- M1 271.94:0.03b £100 isotropic -- M1 340.5 a0.3 1.0 10.1 -- --- -- 389.47i0.05b 1.5 $0.2 isotropic --- E3 442.3 20.1 11.9 $0.8 -- —-- -- 463.0 40.1 2.8 :0.2 --- --- --- 497.3 :o.1b weak --- --- -.. 588.00i0.03b 12.7 i0.8 -0.41:o.02 0.03:0.02 Ml+E2 601.7 :0.2 7.5 20.7 0.90:0.40 -- --- 625.23i0.08b weak -- --- --- 668.10t0.03b 27.3 i1.6 -0.68i0.03 -0.02a0 04 M1+E2 776.8 £0.1b weak -- -- M1 or E3 785.56i0.06b 8.7 :0.5 0.23:0.06 -0.04i0.03 E2 798.89to.06b 8.2 :0.5 -0.22i0.01 0.09:0.02 E2 810.4 to.2 1.6 :0.3 --- --- --- 27 Table 4-1. (cont'd.). Relative Angular Distribution Energy Intensity Coefficients ‘Multipolaritya BY IY Az/Ao Au/Ao (keV) 824.4330.09b 10.3 30.6 0.0930.02 -o.023o.06 E2 830.1 30.1” weak ——— --- --- 836.3 30.1” 4.2 30.3 --- -.. --- 850.5 30.1 1.8 30.3 -- --- ..- 906.9630.06b 5.6 30.6 --- --- 32 916.5330.05b 2.4 30.4 0.3130.03 -o.0330.04 E2 984.93:0.05b 3.9 30.3 0.153o.08 0.063o.1o M1+E2 1059.3 30.1b'c 8.3 30.5 0.2430.04 -o.0730.05 --- 1063.6 30.1 3.2 30.3 0.393o.1o --- --- 1072.2 30.1 2.4 30.3 0.2730.14 --- --- 1143.9 30.1 2.0 30.2 --- --- --- 1151.3 30.1 2.4 30.3 —-- -.. --- 1272.7 30.2 2.3 30.3 -0.1530.10 0.0830.06 --— 1386.7 30.6 0.2030.05 -- -—- -.. 1404.56:0.07b 3.6 30.3 -—- b 1807.14i0.07 19.6 11.3 0.72:0.48 aTransition multipolarity assignments taken from conversion electrons, ref. [W176]. bThese Y-rays were also seen in the decay of 1“36d where the precision in energy was greater. The in-beam studies yielded essentially the same energies, so we have adopted the more precise energy values from [F178]. cThere are two 1059.3-keV transitions in the level scheme; see text. 28 The beam intensity was held as constant as possible (£202) from experi- ment to experiment, the integrated beamecurrent was recorded, and a pulser was included in the spectra to allow reliable normalization of the spectra from one experiment to another. The results for seven pro- minent Y-rays are shown in Figure 4-3, where the intensities have been normalized to the intensity from the 30-MeV reaction. (It should be mentioned that this excitation function procedure was also very useful in eliminating impurity Y-rays from competing reactions.) 4.1.4. Coincidence Spectra The Y-Y coincidence spectra were obtained with a 30—MeV p beam. The lOZ-efficient Ge(Li) detector and a 7.7Z-efficient Ge(Li) detector (energy resolution 1.9 keV FWHM) were used. A standard three-parameter (EY x 5% x t) fast-slow coincidence set-up with constant-fraction timing was used. The coincidences were recorded event-by-event on magnetic tape for off-line sorting with background subtraction. (For more details, cf. section 3-2). Some coincidence spectra are shown in Figure 4.4. The integral coincidence spectrum (all coincidence events as displayed from the 102 Ge(Li) detector) is at the top, and three representative gated spectra are shown below it. Because of the relatively larger backgrounds that had to be subtracted from these gated spectra, they were smoothed (three- channel) to enhance the peaks. The raw spectra and the complete set of gated spectra are shown in Appendix A . A summary of the coincidence data is given in Table 4-2. 29 .mamu > :mm:~ ucocfiaoud woos may mo so>om new mcoauocsw coaumufioxm .muo oppwfim gas: 33cm cased ow mm Om n _ .. 9.38 .. «.0 cm._hwi @90me 3.2: T m.mm0_ L v.0 N mmoom m 352. V w L . m I 0 O r... 3 D. m T ,/ IJQJO 3v . U m... .M r o._ _ — N.- w¢0100-x3m2 30 MSUX— 80 .045 5 3 «3:03 jlntegrol Coincidences '0 t: 33:6 - ‘ I ¢ e' 3: \\ 5. ‘ ,, '7 :668.l-kerGote 200' .. /¢5 "2 it"? - .' § N 600 '9 k I- !2 V -30 a N - a i 1' ° '8 3 {a c IOO' \/ — " ‘ c l E + ’ ‘ o . : 3 442.3-keV Gate 0. L- - 7 a5 ". n m _ co 0 - . .5 200 ‘f 3 g 3 - I 73 1 o IOO'MW o I 0. :27l.9-ke§/ Gate "' /E n /¢=, : q 400- 3 2 an” ' - 000 v o. \ 7’29. 3 200- 5 I w . \/ I ‘ 500 1000 I500 Channel Number Figure 4-4. In—beam Y-Y coincidence spectra for the reaction, 1““Sm(p,2nY) 11+3Eu. The integral coincidence spectrum ("all events") is shown at the top, and three representative smoothed gated spectra are shown underneath. 31 Table 4-2. Summary of coincidence results for the 11+"’Sm(p,2nY)1“3Eu reaction. Gated Y-Ray (keV) Coincident Y-Rays (keV) 117.57 271.94 131.1 668.10 204.2 258.8, 340.2 210.9 588.00 248.4 668.10 258.8 204.2, 340.2 271.94 117.57, 497.3, 785.56, 984.93, 1059.3, 1063.6, 1404.56 340.2 204.2, 258.8, 463.0 389.47 -- 442.3 668.10, 810.4, 1059.3 463.0 340.2 497.3 271.94, 984.93 588.00 210.9, 625.23, 776.8 601.7 916.53 625.23 588.00 668.10 131.1, 248.4, 442.3, 810.4,' 836.3, 850.5, 1059.3, 1272.7 776.8 588.00 785.56 271.94, 1063.6 798.89 830.1 810.4 442.3, 668.10 824.43 1143.9, 1386.69 830.1 798.89 32 Table 4-2. (cont'd.). . Gated Y-Ray (keV). Coincident Y-Rays (keV) 836.3 . 668.10 850.5 668.10 906.96 --— 916.53 601.7, 1072.2 984.93 271.94, 497.3 1059.3a 271.94, 442.3, 668.10 1063.6b 271.94, 668.10, 785.56 1072.2 916.53 1143.9 824.43 1151.3 916.53 1272.7 668.10 1386.69 824.43 1404.56 271.94 1808.9 -- aThere are two separate ~1059.3-keV Y's. bPerhaps there are also two separate ~1063.6-keV Y's. 33 4.1.5. Y-Ray Angular Distributions The p—beam energy for obtaining the Y-ray angular distributions was again 30 MeV. The lOZ-efficient Ge(Li) detector was rigidly mounted with its cryostat on the arm of a goniometer with the face of the detector 15 cm from the target. The data were collected at 90°, 100°, 110°, 125°, 140°, and 155° with respect to the beam direction. The angles were taken in random order for the various experiments, and data were typically collected for 2.5-h at each angle. The 271.94- and 117.57-keV isotropic transitions were used as an internal normalization for the spectra taken at different angles. After the normalization of the Y-ray peak areas, least-squares fits to the experimental angular distributions were made, using the computer code GADFIT [GADFIT]. The fits were made to the equation: I a 1 + (AZ/A0)P2(c080) + (Au/A0)Pu(cose). The parameters extracted from the fit, A2/A0 and Aale, are included in Table 4-1. Angular distribution coefficients not listed in the tables were for transitions that were very weak or that were parts of multiplets and consequently had very large errors. Where a good fit for Au/Ao could not be obtained, the data were refitted with the value for A4/A0 set equal to 0. Some representative angular distributions, together with their calcu- lated fits, are shown in Figure 4.5. The complete set of data with fitted curves is shown in Appendix B. 4.1.6. The 1”3Eu Level Scheme Coincidence information, intensity balances, conversion coefficients, and excitation functions for individual Y-rays were the primary factors used to construct a level scheme for 1L'3Eu. Secondary factors were energy I.2 I. 0.4 O. 3 Y “ l.7 |.6 lniensi |.5 L4 |.3 |.2 LO 0.9 Figure 4-5. 34 MSUX-BO-OBZ 588.0 keV I I T I T T j— I I 668.l keV . A =-0.4Ii-0.02 A2--O 03:0 02 A2=-0.68i 0.03 " 4" ° ' A4=’0.0210.04 ‘ _. 785.6 keV 9'5-5 “V . A2=0.2330.06 i 42:03: 30.03 3 - A4=-O.04i'0.03 A4=-O.03 30.04 ' 3 KS" 1 30° l 50° L 76° 1 95° “3° 1 30° L 55° L 70" 1 90° Blob Four representative angular distributions of 1L'3Eu Y rays together with their fits calculated by the code GADFIT. The points correspond to 90° 110°, 125°, 140°, and 155°. and the backward angles, 100° I 35 summing relationships, input from the known lkacdm+g decay scheme [F178], and angular distribution data. The spin and parity assignments were made on the basis of angular distribution coefficients, conversion. coefficients, and input from the 143de+g decay scheme. The resulting level scheme is shown in Figure 4-6. For comparison, the level scheme of 1L'3Eu obtained from the decay of 173de+g is shown in Figure 4-7. Speci- fic details of the construction of the level scheme and J1' assignments are discussed next. Ground, 271.94-, and 389.47-keV States The most intense Y transition in the in-beam, as well as the off- line, experiments is the 271.94-keV transition, which is in coincidence with the 117.57-keV transition (and with six others - cf. Table 4-2). 0n the other hand, no other Y rays appear to be in coincidence with the ll7.57-keV transition. This leads to the adoption of a cascade, with the 117.57-keV transition on top of the 271.94-keV transition, and places states at 271.94 and 389.51 keV. The upper state is also depopulated directly by the 389.47-keV transition, and this energy is adopted for the state. The ground state has been reported to have JTr I 5/2+ [Ec72], and the 271.94- and 389.47-keV states have been assigned 7/2+ and 11/2', respec- tively, on the basis of the multipolarities of the three above Y transi- tions and the logft values for 1“3de B-decay. Also, in the ll'3de decay studies, the 389.47-keV state was measured to have a half-life of 50.0:0.5 usec. In this present work it has been found that the 117.57- and 271.94- keV transitions are definitely isotropic and the weaker 389.47-keV transi- tion probably isotropic. Although this information does not allow one to n , comment further on the J assignments, it is consistent with the long Figure 4-6. 36 ...I I. .I‘ 0'} ‘\ o b‘ ‘5 5.0.}? “I x ' u ‘ ”(.5 __ Mi?” 23592 1211' \ 1.‘ “29‘ My / 23732 F ~$€:T 1. -ie Zuni- I V‘s—.5: ‘ Lam-LL O 1112 13121: ~15 a”? or‘ mass mzi 13121 ~.° . 556) 2121-2 '912‘ (\\6\ P ‘3' 'I 20133 I l v 5‘ Q” t l I u 1 \ ‘5' . 1 1 ' 13°15‘93“ 030; L j___.La.Q.l.I. , :3. i T 60“” ;. , ‘ 13239 I O ' . . \ ' 1112' 1 ' ' I 3“.” ’3’ 0 Iraq-L - ' I v o ‘— ‘31L '1 1 1 l x’ .\ Pp_ 9 132113 T Y’r v o 5’ \\ '1112: 1 2 ' 1 <18": 130a? l I I r ' T .9 I I I l I I S" Q? i 1 1 1 1 1 h 449” H: : : ~ ~.' “9.33 I I I I ' "5| .0 LILL'ZL—\ - . I 1 I I 6999- 3, ‘0‘} 1331-2 51 ' 1 1 . . 1 \°\b. 9 F‘fi :Uzz’ r 1 1v 5 f I Q m-Q‘I‘..QQ \q.—.fi__—/ 13 6 I I 1 I 9J1, to q‘ «'fl 523‘ .7 - I v 1 r I v '0‘ o m I 712 - i 3 ‘E f f I «9‘9‘5: o 3: ‘5— 1213-29 "‘2 I r! r I v : 912‘ [Li if z I 99 J9: o 9174? 5M1? " 1 ' ‘9 9‘. iijmuu I I I . 0' 1112-312 312) . ' I ' ‘3” IQEI I I l I | I : : N N : ' . . 61 «N :NUN 999 I I ‘\ \- ' ' I I a a bfifio." 4 ' .112+ : l 1 ' "‘ g1“!— cox—M 7— ‘V r o \ ‘ “1112‘ 311 ,1 no ; i j i 5“ .'\ ° 3139-47 . . 9 9 '712" i 1 {10‘5” 271 94 x w A I" U '5/2+ o ll+3Eu level scheme as determined by the 1L'L'Sm(p,2nY)1L'3E2u reaction. The asterisks before JTr assignments indicate that we relied heavily on the 1°3de+9 B+/e decay [F178] for these assignments. Also. the dashed Y transitions are weak transitions seen in 143de+g decay but not seen in our in—beam studies; however, they originate from levels seen in the in-beam studies. t should be noted that there are two 1059.3-keV transitions in this level scheme. 37 "/2' llZax ll2’ O 3956c I43 0. 6.4 MeV (est) 64Gd79 3+ 6' §\ 9‘0 bu- Q.“ LOG FT I/2.3/2+ __}°‘ _ of." _ _ 0216/ %.l I 6.4 I/2.3/2“ _[ (F; __ _ _ I543.o I.2 6.4 66B6\ \ .\ O I/2 3/2‘.’ \ 5:09 \ 1‘ / 1 9L \OO‘QQ- 8I2 :/ 7.2 5.9 «\ 5x + I 63.0“. 166 V2 II 3, 46:.:/ 34.2 5.4 3/2 I ”96¢ 2588 56.3 5.2 5/2” , 3 2.6lmin Decay schemes of 1“Gd? and 1“’3de from Ref. [F178] for Figure 4-7. comparison with our in-beam studies. 38 0a“ I" M 1121...; I“36:1 64 79 9 us 61 IYJ 3.. @1146 56% I FE Egfii aniezstz N7 6.! (35%” Figure 4-7. (cont'd.). 39 half-life of the 389.47-keV state (plus the complex feeding into the 271.94-keV state). 258.81-, 463.7-, and 804.1-keV States The other set of low-lying states, presumably of lower spin, has the interconnecting transitions of 204.77, 258.81, 340.5, and 463.7 keV. Coincidence relations among them and the intensity balances lead to the placement of levels at 258.81, 463.7, and 804.1 keV. The first two were observed in 1“3Gdg decay [F178]; the 804.1—keV state has not been pre- viously observed. Spin assignments for these states were not possible from angular distribution coefficients because all the Y transitions were very weak and had large errors on the values for the transition intensities. How- ever, the 258.81- and 463.7-keV states were assigned 3/2+ and 1/2+, res- pectively, from ll‘3Gdg decay; presumably their major components are the was/2 and Irsl/2 single-particle states. Not much can be said about the 804.1-keV state. Its being connected to the 463.7-keV state indicates more that it is related to the 51/2 state than what its spin is; for example, it might be [2+ x s1/2]1/2+, 3/2+, 5/2+ —- any one of these would selectively deexcite to the 463.7- keV state. On the other hand, one might anticipate some feeding from the many higher-lying 9/2 states (cf. below) to a 5/2 state, making 1/2+ or 3/2+ the preferred assignment. Arguments based on missing transitions are rather weak, however, so one is more safely left with the possibili- ties, 1/2, 3/2, or 5/2. 977 . 47-keV State This state feeds into the 11/2" 389.47-keV state by the 588.00-keV transition. Although the 50.0-usec tl/2 of the 389.47-keV state makes 40 this impossible to confirm by a direct coincidence measurement, the other coincidence relations with the 588.00-keV Y confirm this placement, as did the extensive coincidence relations from 1“3de decay. From 1“3de decay the 977.47-keV state was tentatively assinged 7/2‘. However, if the 588.00-keV transition is a mixed Ml/Ez transition, the Jr assign- ment is restricted to 9/2'. 11/2', or 13/2‘. The ll/2' value is ruled out because of the large negative value of A2 and the small positive value of At. The fact that this state is not fed by Y rays from high- spin states indicates that it most likely is not in the yrast sequence, eliminating J7r - 13/2'. Below we shall show that the 1057.57-keV state has J1r - 13/2' and receives feeding from the high-spin states. It thus appears to be the 13/2' yrast state, making the possibility of a lower- lying 13/2' state unlikely. This state can therefore be assigned 9/2‘. 1057.50-keV State The coincidence information between the 785.56- and 271.94-keV 7's places this state. It was also seen in 1“3de decay, where it was tenta- tively assigned 9/2+ or 11/2+. The 52 multipolarity of the 785.56-keV transition allows J1r values from 3/2+ to ll/2+. The angular distribution data for this transition, however, can be fitted by only two values, 3/2+ or 11/2+. The positive value of A2 and small but negative value of Al+ indi- cates the transition is a stretched E2, eliminating an otherwise possible 4- 7/2 . From 1“3de decay 3/2+ can clearly be ruled out, leaving J1r - 11/2+ for this state. 1057.57-keV State Again, the SO-usec t1/2 of the 389.47-keV state prevents a direct coincidence measurement to place the 1057.57-keV level feeding into it, 41 but the eight other transitions seen in coincidence with the 688.10-keV transition place the 1057.57-keV level quite securely. This type of argument will not be belabored henceforth but applies equally well to many of the states discussed below. This level was also placed in 1“3de decay and tentatively assigned 13/2’. The M1+E2 mixed multipolarity of the 668.10-keV transition limits its J1r to 9/2‘, 11/2' or 13/2‘. The large negative A and small A“ rule out 11/2‘. Since the 668.10-keV y 2 is seen so intensely in the in-beam experiments, yrast arguments lead to a preference for the higher spin, i.e., l3/2‘, for this state. 1188.36-keV'State This state, placed by coincidence information from its deexciting 131.1- and 210.9-keV transitions, was confirmed by the strong 798.89-keV transition feeding the ll/2‘ 389.47-keV state. The pure £2 multipolarity of the latter transition could indicate a stretched quadrupole transition, but the negative A2 and A“ values establish it to be a J +IJ pure quadru- pole transition. Its J1T would thus be ll/2’. The tentative 9/2' assign- ment reached from 1“3de decay data is believed to be incorrect because the negative A“ value also rules out a mixed Ml/Ez multipolarity for the 798.89-keV transition. 1213.90-keV State The 824.43-keV transition that deexcites this state to the ll/Z' 389.47-keV state is an 32, which limits its JTr to 7/2‘ through 15/2'. The angular distribution coefficients limit this further to 7/2‘. (The value of A2 is too small for a 15/2“ + ll/Z- transition; cf. the 785.56- keV transition from the 1057.50-keV state.) This state was left unassigned in the 1“3de decay studies: J7T = 7/2' should not be allowed with a 42 logft value of 6.5. However, if it is assumed that much of the intensity of the 824.43-keV transition in 1“3de decay results from missing unde- tected transitions from higher-lying states [F179], then a considerably higher logft value, consistent with the 7/2' assignment, is expected. 1256.87-keV State For the 984.93-keV transition that deexcites this state to the 7/2+ 271.94-keV state, Wisshak et al. assigned M2+E3 mixed multipolarity. According to the argument in Ref. [F178], this assignment was wrong because of the use of an incorrect GK value -- the latter calculation indicated Ml+32 multipolarity. The in—beam angular distribution results of the experiment are consistent with a (stretched) quadrupole transition Since the experimental UK is (6.9 i 1.4) x 10'3, and the calculated “K is 1.6 x 10.2 [Ha68] for an M2 and 3.4 x 10"3 for an 32 transition, the M2 can be excluded. Thus, the 1256.87-keV state has J1T a ll/2+. 1306.00-keV State The 916.53-keV transition (although it has a fairly large error in intensity) deexciting this state appears to be a pure stretched 32. Its angular distribution pattern restricts the J1T value of the state to 7/2- or 15/2‘. Yrast considerations suggest a preference for the larger value of 15/2‘. (Also, the A2 is uncomfortably large for a J + J + 2 transi- tion.) 1331.2-keV State + + The J1r of the state is restricted to 3/2' or ll/Z' because of the angular distribution coefficients of the 1059.3-keV transition (whose multipolarity has not been determined). The 3/2i value can be ruled out because the (p,2ny) reaction is not likely to populate low-spin states at 43 higher excitation energies. (Also, again the A2 appears to be too large for a J-fiJ + 2 transition.) From the 1“3de decay data 3/2i can also be excluded. An 11/2' assignment would require the 1059.3-keV transition to be M2, and, although this cannot be definitely ruled out, we prefer the 11/2+ assignment. (Also, see the remarks below about a second, weaker 1059.3-keV transition.) 2378.2-keV State This state, the last one for which it was possible to make a unique JTr assignment from the in-beam data, has its JTr restricted to 11/2' or 19/2' because of the large A2 value. Its decay solely to the 15/2' state and its large papulation in the (p,2ny) reaction would lead to a prefer- ence for 19/2'. Other States The remaining states in the level scheme in Figure 4-6 were placed on the basis of coincidence data, corroborated by B-decay data and energy sums. Their J1r values could not be determined uniquely from the present experimental data; however, some JTr values could be excluded on the basis of the angular distributions. Also, some of these states observed in the in-beam work had their assignments made from 1“3de decay - these are indicated by asterisks on the level scheme. And five transitions have been included (dashed lines) that were seen in 1“3de decay but not in the in-beam experiments. It is worth mentioning that there are two 1059.3-keV transitions: in addition to the one deexciting the 1331.2-keV state (cf. above), coincidence data indicate another, weaker one deexciting a state at 2559.4 keV. 44 4.2. Triaxial Calculations and Discussion A total of 31 states in lggEueo, many of which had not been populated by 143Gd 8 decay, was deduced from our in-beam.y—ray experiments. For the purposes of discussion these states can be classified in three cate- gories: l) single-quasiparticle states, 2) negative-parity collective states, and 3) positive-parity collective states. 4.2.1. Single-Particle States The four states at 0-, 271.94-, 389.47-, and 463.7-keV can, as ex- pected, be described as consisting primarily of the was/2, 697/2'1, "911/2: «31/2 single-quasiparticle states, respectively -- four of the five possible single-proton states between 2 = 50 and z - 82. These states have not been confirmed as single-particle states by direct trans- fer reactions (no target exists for a straightforward reaction), but similar states have been populated with large spectroscopic factors at comparable positions in N - 82 nuclei [Ne70]. These four states in the N = 82 isotones have also been successfully analyzed by de Takacsy and Das Gupta [Ta76] as single-quasiparticle states. It is important here to mention that the 3/2+ state at 258.81-keV probably does not consist primarily of the nd3/2 single-quasiparticle state. The major component of the "dB/2 state, which is more fractionated than the other four single-proton states, lies above 400—keV in the other N a 80 odd-mass isotones [Le78]. Thus, it is unlikely that it should lie at such a low energy in 1"’3Eu. (A state observed at 819.9-keV from 1“3Gdg decay may very well contain a major portion of the "d3/2 wave function.) Also, the calculations (discussed below) show the 258.81—keV state to consist primarily of the was/2 state coupled to the 2+ 1"’ZSIn core. 45 4.2.2. Negative-Paritngollective States There are a number of hopefully equivalent ways to describe and interpret the more complex, higher-lying states for odd-mass nuclei in this general region: From the standpoint of B decay alone, a three- quasiparticle (or multi-quasiparticle) approach has worked quite well [Ep71], and it has the advantage of simplicity, almost an exaggerated simplicity. The other extreme of this picture is to use a weak coupling (decoupling) model in which the single-quasiparticle states are coupled to simple phonon excitations of the 1l+2Sm core. A rather qualitative version of this, using the five single-proton states coupled to the 2?, 0T, 2;, 4:, and BI vibrational states, was discussed in ref. [F178]. The two most noteworthy recent quantitative approaches are the triaxial weakrcoupling model described by Meyer-ter-Vehn [Me75] and the inter- acting boson-fermion model of collective states developed and described by Iachello and Scholten [I379]. These calculations have been performed using a computer code modified from that of Meyer-ter-Vehn; unfortunately, the only extant calculations of Iachello and Scholten relate to the odd- mass Eu isotopes above M a 82. Thus, the discussion will be limited here to the triaxial weakrcoupling model and it is hoped that in the near future the interacting boson-fermion calculations can be extended to 1“Flu and its neighbors. The negative-parity collective states in 1“3Eu are expected to con- sist primarily of the "fill/2 state coupled to a triaxial core. The lowest excited states of the adjacent even-even nucleus [Le78], 1“23m, were used in order to determine the deformation parameter 8 and the asymmetry para— meter 7. Since the triaxial model applied to the even-even neighbor(s) does not distinguish between prolate (O°$YS30°) and oblate (30°sys60°) , 46 deformations, the calculations were performed for both types. The results are shown in Figure 4-8. For a prolate shape (Y = 23.5°) the agreement with experiments is not good, either in the energy separations or even in the ordering of the levels. The calculated energies of the second 11/2‘ state (1897.0 keV), the first 9/2' state (1186.0 keV), and the first 13/2' state (1508.0 keV) are considerably greater than the experimental values. Also the prolate calculation places the first 7/2' state at 979.0 keV; if it were to lie this low, it should have been seen experimentally. These contradictions place doubt on 1‘*3Eu being prolate. Actually, a prolate- oblate shape transition between N a 77 and N - 79 in the GoNd isotopes has been reported by Gizon et al. [6178], so 1“3Eu might be expected to be oblate. Calculations were made for oblate shapes at both Y = 36.5° (60°-23.5°) and Y = 60°. The agreement with experiments is much improved, both in the level ordering itself and in the energy separations of the lower states, with the exception of the first 15/2‘ state. The calculated energies of the first 9/2‘ (900.0-keV), first 13/2‘ (1058.0), first 15/2' (1365.0), second 11/2‘ (1386.0), first 7/2’, (1472.0), and first 19/2‘ (2655.0) states at Y = 36.5° confirm the oblate shape for 1l+3Eu. Additional evidence for triaxiality includes the second and third 11/2- (1386.0- and 2295.0-keV)states,as well as the second and third (2220.0- and 2506.0-keV) 9/2' states, in decent agreement with their experimental counterparts. Thus, the higher-lying states appear to favor a triaxial description in preference to a pure oblate shape. 3.5 3.0 in Excitation Energy (MeV) b 0.5 0.0 Figure 4-8. 9’ u 47 '80! cIO-OC" Prolote Exp. Oblote 7823.5' 7836.5“ y=60° ,8: O.l43 £20.54 I8=OJ25 A= 0.94 Mev A=O.94Mev A=O.94Mev xf=0.8 1,808 $930.8 Energies of calculated excited negative-parity states in 1l+3Eu compared with our experimental findings. We calcu— lated these energies using a triaxial weak-coupling model, coupling the "hll/Z state to a deformed core. Results for both prolate and two different oblate deformations are shown; a slight oblate deformation seems indicated. Spins are shown in 2J. 48 4.2.3. Positive-Parity Collective States The positive—parity states can be generated by coupling the "ds/z and flg7/2-1 states to the triaxial core. Here the results are consider- ably poorer because of the ease of mixing with close-lying states having the same positive parity. In Figure 4-9 the results of the calculations using the oblate shape Y of 36.5° are shown for coupling "pure" nds/z and wg7/2'1 to the 1“ZSm core. The nd3/2 coupling leads to the 3/2+ state 258.81-keV. This indi- cates that the 258.81—keV state is primarily a collective state and not the «d3/2 single-quasiparticle state. In fact, the nd3/2 state has been observed at 405.0 and 403.9 keV, respectively, in lggPr and lgiPm, and lies even higher in the other N a 80 odd-mass isotones. The calculated 1/2+ state from the "dslz coupling lies at 789.0 keV and could correspond to either the 804.1-keV state observed in our experi— ments or the 812.9-keV state observed in 11“3Gdg decay. The second 3/2+ and second 1/2+ state from this coupling are predicted to lie at 1546.0 and 1929.0 keV, respectively. No such low-spin states were excited near these energies in the in-beam experiments, but the two 1/2+ or 3/2+ states found at 1543.0 and 1723.6 keV from 1“3Gdg decay might have a loose correspondence to them. The ng7/2‘1 coupling predicts the first 11/2+ state to lie at 1061.0 keV. This corresponds to the experimental state found at 1057.50 keV. Finally, the “dB/2 coupling predicts a 9/2+ state lying at 732.0 keV, and the ng7/2‘1 coupling, one at 950 keV. The experimentally observed 9/2+ state at 906.96 keV deexcites directly to the ground state and not through the 271.94 keV state. This would indicate that it con- sists primarily of the Irds/2 coupling. 49 MSUX-IO-OCC ______ + ——a 3+ _ 9+ _ + _ é + . 2'5 A fi+ — I9; t 3+ —-9+ ":— II ,I5 5* 3+ 71 :I: :3" 7” 719:6 ——-ll"' "_\_ + _, :29" 9+ 9i i -—\ 7+ ' a I =—-—-ll ,I9 9+ 3 7+ II" \"54' ,. ...—‘54- 9" 3* a — 5 3+ l' 2 l5- __”1 1 ‘2 __f ... l5" ‘2 __<_-—\——‘II‘.3— __/-—/7+ '6 I.o- 5+ "ti- ‘- "’"+ 4 II‘I 7+ ”—9“ """" 9+ ._______|'*—4r--- I+' 9*” .+ 0.5- ____|+ 5 - —---ll: 3"". 4;... —————— 7+ 60 5+---- 5+ d5,2 + core 97/2+ core y=36.5° ExP- 7:365" fi=0.|50 B=0J54 A=0.94 A=0.94 76f3(3.6’ 7tf=u=o zosmaowwmm Houseman < .NIm ouswfim “>9: Stocm >3”. I». OOON 000. 00m 00m 00. on 0000 . _ 1 fl]. . d,. . . a . . AUh: I L r 1 Ha r I 3 n u w n. I..- .O. N. 3 I . 3 1 I? Y L “I’. r - D. n 1 8 ... u w T 6628 3x5 4.: . r . . . _ P . . . . p. _ . _. h P p .u p 1 AV— n 55 Table 5-1. Energies, relative intensities, angular distribution coeffi— cients, and multipolarities for Y transitions in 1“Pm from (p,2nY) reactions. Relative Angular Distribution Energy Intensity Coefficients Miultipolaritya E Y I Y Az/Ao Au/Ao (keV) 196.620.1b ;18S.7:11.2c -o.oz:o.01 -o.oz:o.01 Ml 197.310.2b ? ..- --- --- 208.720.1b weak -.. -.. -.. 247.4:o.2 1.5:o.2 -o.2s:o.12 —o.03:o.19 --- 324.620.1b 6.8:0.5 -0.08:0.02 0.05:0.03 Ml 402.6:0.2 2 --- ..- -.. 403.820.1b 31.3:1.9 -o.1o:o.02 0.04:0.02 Ml+EZ 431.820.1b 5100 isotropic --- M2 438.8:0.l 12.7:1.2 ~0.28:0.22 0.25:0.25 E2 524.9i0.2 weak -- --- --- 531.3:o.2 3.2:o.3 0.15:0.08 0.19:0.11 -- 538.5:0.2 l8.9il.2 -o.34:o.02 0.02:0.02 Ml 607.9:0.2 3.6:0.5 -0.06:0.06 -0.06:0.10 --- 628.620.1b 7.1:o.5 0.01:0.02 0.01:0.04 --- 640.5iO.2 weak --- -—— --- 653.920.2b 1.2:o.1 ..- ..- --- 684.720.2b 28.9tl.8 -o.77:o.01 0.06:0.02 M1+E2 694.0:0.2 8.4:0.8 -o.11:o.04 0.09:0.06 --- 702.1:o.1b 5.4:0.6 -o.9o:o.03 -o.15:o.06 --- 728.3iO.lb 12.8:0.8 -o.05:o.03 -0.60:0.ll -- 749.6:0.1 3.4:o.4 --- --- --- Table 5-1. (cont'd.). 56 Relative Angular Distribution Energy Intensity Coefficients Multipolaritya EY IY AZ/AO AH/AO (keV) 777.610.1b 35.8:2.1 0.27:0.01 -o.os:o.01 22 785.310.2b lO.6:0.8 -o.34:o.04 0.04:0.06 22 820.6:0.2 1.9:0.6 --- --- --- 827.9:0.3 1.4:0.5. --- --- --- 837.110.1b 29.9:1.9 0.20:0.03 -o.06¢o.04 --- 858.5:0.3 l4.1:0.8 0.26:0.01 -o.02¢o.01 --— 882.010.1b 29.5:l.8 0.26:0.02 -o.11:o.oa --- 911.4:o.2b 16.1:l.0 0.04:0.02 0.12:0.02 E2 924.7iO.3 weak --- —_- --- 956.5:o.3 9.8:0.7 -o.3o:o.07 -o.03:o.12 -- 995.710.2b 6.6:0.5 0.44:0.06 0.06:0.09 --- 1008.7:o.3 5.0:o.4 -o.43:o.04 -0.10:0.06 —-- 1037.5:o.3 4.1:o.3 0.35:0.09 -0.03:0.l6 -- 1045.9:o.4 3.5:o.3 0.14:0.01 -o.13¢o.oz --- 1153.3:o.3 1.0:o.2 -o.49:o.05 -o.14:o.11 --- ll63.0:0.3b 3.4:o.3 0.29:0.03 -0.ll:0.06 --- 1242.5:o.4 1.7:o.2 -o.1s:o.oe -o.os:o.09 -—- 1495.9:o.4 1.9:o.2 --- --- --- l786.3:0.4 0.6:0.2 --- --- --- aTransition multipolarity assignments taken from conversion electrons, ref. [Ke77]. bThese y-rays were also seen in (o,4nY) reaction. Therefore, the Y-ray energies are the average of (p,2nY) and (a,4nY) reactions. cPart of this intensity belongs to 197.3-keV transition. 57 lGZ-efficient Ge(Li) detector (energy resolution 2.6 keV FWHM), were used. More detail on the electronic set-up is discussed in section 3.2. A resolving time of 21 z 100 nsec was also used. In Appendix C, important coincidence gates which were used to make the level assignments are shown. The coincidence information was used to construct a tentative level scheme. The data from the angular distribution and singles spectra were then used to lend support to the level scheme. Construction of the level scheme and spin assignments will be discussed in section 5-3. A summary of the coincidence data is given in Table 5—2. 5.1.4. Y-Ray Angular Distributions The p beam.energy of 25 MeV was obtained for the Y-ray angular distribution experiment. The detector used was a l7Z-efficient Ge(Li) detector. The detector was positioned as discussed in section 3.3. The set of angular distribution data for lkle consists of spectra taken at 90°, 100°, 110°, 125°, 140°, and 155°. The angles were taken in random order for the various experiments and data were typically collected for 2.5 h at each angle. The 431.8-keV isotropic transition is used as an internal normaliza- tion for the spectra taken at different angles. Peak intensities were derived from the peak fitting program SAMPO [R069], and fitted to the equation I =- 1 + (AZ/A0)P2(cose) + (Au/A0)P1,(cose) using the least squares fitting computer code GADFIT [GADFIT]. The para- meters extracted from the fit, A2/A0 and Aulao are included in Table 5-1. The A2 and Au values for 196.6- and 628.6-keV transitions turned out to be close to zero, as we expected them to be isotropic due to deexcitation 58 Table 5-2. Summary of coincidence results for the ll*sz (p,2nY) 1L”Pm reaction. Gated Y-Ray (keV) Coincident Y-Rays (keV) 196.6 197.3, 431.8, 531.3, 607.9, 640.5, 653.9, 684.7, 694.0, 777.6, 820.6, 911.4, 956.5, 995.7, 1045.9, 1163.0, 1495.9, 1786.3 208.7 196.6, 431.8, 1037.5 247.4 538.5 324.6 403.7 (402.6 +,403.3) 196.6, 324.6, 728.3, 749.6, 911.4 431.8 196.6, 208.7 438.8 -—- 531.3 196.6 538.5 247.4, 924.7 607.9 196.6 628.6 --- 640.5 196.6, 1037.5 653.9 196.6, 777.6 684.7 197.3, 702.1, 785.3, 858.5 694.0 196.6, 911.4 702.1 684.7 728.3a 402.6, 882.0 749.6 403.8 777.6 196.6, 653.9, 820.6, 995.7, 1008.7 785.3a 684.7 820.6 196.6, 777.6 827.9 196.6, 777.6 59 Table 5-2. (cont'd.). Gated Y-Ray (keV) Coincident y-Rays (keV) 837.1 1037.5 858.5 684.7 882.0 728.3 911.4 196.6, 402.6, 694.0 924.7 538.5 956.5 196.6 995.7 196.6, 777.6 1008.7 196.6, 777.6 1037.5 196.6, 208.7, 640.5, 837.1 1045.9 196.6 1163.0 196.6 1495.9 196.6 1786.3 196.6 aThere are two transitions with this energy in the level scheme. 60 from the 628.6-keV isomeric state. The values of Az/Ao were, in general, more reliable than the values of Aa/Ao and could be used to estimate the mixing ratios for the more intense transitions. The data with the fitted curves for some of the Y-rays are shown in Appendix D. 5.2. Experimental Details and Results for the (0,4nY) Reaction 5.2.1. Target and Reaction By using an a beam, the high spin excited states in lule were populated via the 1L'lPr(01,4nY)1L*1Pm reaction. A target was prepared by drying a thin slurry of 99.9% enriched 1“1Pr203 onto a thin formvar backing. The a-beam particle beam was produced in the MSU sector-focused isochronous cyclotron. The beam current required for these experiments was about 10 us for most experiments and was readily obtainable for the runs. The reaction cross section for (o,xn) reactions as a function of alpha particle energy was calculated using the code CSBN [CSBN] which is shown in Figure 5-3. The maximum cross section for (0,2n) through (0,4n) reactions are spaced about lO-MeV apart. According to Figure 5—3, the best alpha particle energy for (0,4ny) reaction in order to minimize the production of contaminant Y-rays would be 54 MeV. At this energy, the amount of contaminant production (a,3n) and (0,5n) is about 4% of the total cross section. The highest energy alpha beam, 47 MeV, which could be obtained by the cyclotron was used for the 1‘*1Pr(01.,4nY)1“‘1Pm experiments. By using a 47¢MeV alpha particle, the amount of the main contaminant lusz is going to be about 34% of the total cross section. The other contaminants pro- duced directly to a lesser extent would be ll+3Pm and 1“Nd. The EC/B+ decay of 1l+1Pm and 11+2Pm also produce identifiable Y-rays from states in 61 (a, Xn) on '4'Pr 3N LIN 5N +’*“ y—e O H I CROSS SECTION IN MILLIBARNS 10" ° 1° LA§°ENE§°6Y IR? MEVSO 8° 7° Figure 543. Excitation functions for ll+1Pr(o,xn) reactions calculated using the code CSBN. 62 1“Nd and 1”Nd respectively. These predictions were observed in the experiments. Some other impurities came from the reaction of alpha particles with oxygen in the target. 5.2.2. YrRay Singles Spectra The detector which was chosen for the singles experiments was a 7.7%- efficient Ge(Li) detector (with a resolution of 1.9 keV FWHM). This detector was placed at 125° with respect to the beam direction and the counting period was typically about 2.5 h at counting rates of 46000- 8000 cps. A capper-cadmium absorber was used to shield the detector from x—rays which would otherwise dominate the spectrum. In Figure 5-4, a singles Y-ray spectrum is shown. The general experimental techniques and data analysis used were the same as discussed in section 3.1. Several radioactive sources,such as 60Co, 1528u and 226Ra,were used to perform energy calibrations. An efficiency curve for the detector was obtained (Figure 5-5) and relative intensities for the transitions were determined. A total of 33 Y-rays were assigned to lkle from (0,4nY) reaction on the basis of singles spectra and coincidence experiments discussed below. Energies and intensities of peaks that are believed to belong to 11”Pm are listed in Table 5-3. The relative intensities of those transi- tions which were part of doublets and were not able to be resolved are indicated by question marks. In general, Y-rays are not listed in this table unless coincidence information demands that they should be. Since most of the contaminants are known to be lusz, 1“Nd, and lthd, the energies of these Y-rays are not included. Also, this table includes angular distribution coefficients and transition multipolarity assignments which will be discussed later. 63 3500 3000 CHANNEL NUMBER 2500 .2225 3a 3260 - - .cm «2| e2e... 0.:nI - 11 EN?- m b n 3 . nnvI II 604.47 62 II o..nm\m.o~eI «... .MOVI no..- nan! ,, m nu ndvnl 2 mVQNnII ¢A¥MII Banzl Eu 0 Elmo? saws, com I . 5 . 0.00 I IN DON 02.9 ms... 00% EQN!\ O .6..- w ...af l Edna mfi:!\. - 62»! $28. Educ? nxnmzl - , u b 5 5 4 O w W0. 0 m Y-ray singles spectrum of 1"'1l’r(01,4ny)“’1Pm taken Figure 5-4. with a 7.7%-efficient Ge(Li) detector placed at 125°. 64 .30 cm mo museumav Heuomumn Imuusom m sags nouumumc Afiqvmu ucmfioamwmuum.m m new m>uso kucmfiqumm Heuomumv < .mlm muzwfim 393 >995 >om in 0000 000m 000. 00 00m 00. on . q . —44 _. 4‘ 1 . . _a. 1. . q F*U_ T L T .. H r. L m m u w m u N. I L. .o. a L ...: r H j J m r l «a w 4 nu w M .M n. Lao. r L w .5828 2..va $2. W F L m p h n — .L p p p p p b — . p p p P . 1 no. 65 Table 5-3. Energies, relative intensities, angular distribution coeffi- cients, and multipolarities for Y transitions in 1“1Pm from (o,4ny) reactions. Relative Angular Distribution Energy Intensity Coefficients Multipolaritya EY IY Az/Ao Au/Ao (keV) 108.9:o.2 2 -.. --- --- l40.6:0.2 10.3:1.2 -o.13:o.07 -o.03:o.1o --- 196.610.1b 338.1:8.6c -0.06:0.06 -o.02:o.07 Ml 197.320.2b ? ..- --- ..- 206.6:0.2 weak --— _—— ..- 203.730.1b 2 --- -.. -.. 218.6:0.2 3.1:o.2 --- ..- --- 315.4:o.1 33.8:O.8 -O.18i0.05 0.02:0.07 '--- 324.6:0.1b 5.7:o.3 -0.26:0.07 0.02:0.09 Ml 346.3:0.2 10.9:o.4 -o.44:o.03 -o.01:o.o4 --- 381.3:o.1 106.6:2.S -o.11:o.03 0.02:0.05 --- 403.8iO.1 2.7:0.4 -- -- Ml+E2 426.9:0.1 21.2:o.9 -o.39:o.04 0.03:0.05 --- 431.8:O.1b 2100 0.02:0.02 0.04:0.04 M2 455.1:o.2 7.8iO.7 0.30:0.06 0.04:0.08 -- 464.810.2 5.1:o.5 -o.22:o.os 0.12:0.07 -- 628.6:0.lb 6.1:O.4 0.07:0.05 0.04:0.04 —-— 639.0:o.1 43.9:1.1 -o.02:o.03 0.02:0.04 --- 553.9:o.2b 4.2:o.s -o.so:o.07 0.08:0.10 --- 684.7:o.2b 11.2:0.4 -0.89i0.02 0.08:0.03 Ml+E2 66 Table 5-3. (cont'd.). Relative Angular Distribution Energy Intensity Coefficients Multipolaritya EY 1'Y AZ/Ao Au/Ao (keV) 702.1:o.1b 3.5:o.3 -o.59:o.02 0.01:0.03 --- 728.3to.1b 22.3to.5 0.23:0.03 -o.02:o.os --- 777.6i0.lb 10.3:o.2 0.32:0.04 0.01:0.06 32 735.3:o.2b 1.3:o.2 -o.93:o.09 0.27:0.12 £2 837.1i0.lb 3.1:o.2 0.22:0.08 -o.oe:o.12 --- 882.010.1b 35.1:2.1 0.06:0.02 -o.02:o.04 --- 911.420.2b 1.4:o.2 -- --— 22 990.8:o.2 16.0:o.4 -o.22:o.02 0.02:0.03 -- 995.7:o.2b 4.810.2 0.41:0.03 0.03:0.04 -- 1020.3:o.3 5.1:o.2 -o.03:o.03 -o.04:o.04 --- 1112.7:o.2 4.1:o.2 -o.15:o.04 0.18:0.05 --- 1163.0:o.3b 1.5:o.1 0.15:0.06 0.02:0.09 --- 1359.6i0.4 weak --- ..- --- aTransition multipolarity assignments taken from.conversion electrons, ref. [Ke77]. bThese y-rays were also seen in (p,2nY) reaction; therefore, the y-ray energies are the average of (p,2ny) and (a,4ny) reactions. cPart of this intensity belongs to 197.3-keV transition. 67 5.2.3. Coincidence Spectra Using the same geometry and electronic set-up described in section 3.2, three-parameter coincidence events were recorded on five magnetic tapes, each containing 3 x 106 events. The detectors used were both of large volume (7.7% and l6Z-efficient) and the TAC resolving time was about 21 a 4 nsec. The coincidence gates for most of the transitions which have been placed are shown in Appendix E. The coincidence information was used to construct a tentative level scheme. The data from the angular distribution and singles spectra were then used to lend support to the level scheme. Construction of the level scheme and spin assignments will be discussed in section 5-3. The results of the coincidence measurements are summarized in Table 5-4. 5.2.4. y-Rays Angular Distributions A 47-MeV a-beam produced by the MSU cyclotron was used for y-ray angular distribution experiments. The 7.7Z-efficient Ge(Li) detector was mounted on the arm of the goniometer apparatus as described in section 3.3. The data were collected at 90°, 110°, 125°, 140°, 150°, and 160° with respect to the beam direction. The angles were taken in random order for the various experiments, and data were typically collected for 2.5 h at each angle. A normalization was provided by using a stationary l6Z-efficient Ge(Li) detector. The resulting distributions were fitted to an expansion of Legendre Polynomials to give the experimental Az/Ao and Au/Ao coeffi- cients. These are listed in Table 5-3. The A and A” values for 196.6-, 2 431.8- and 628.6-keV transitions turned out to be close to zero; we 68 Table 5-4. Summary of coincidence results for the 1MPr (o,4ny) 1“Pm reaction. Gated y-Ray (keV) Coincident y-Rays (keV) 108.9 324.6, 403.8, 728.3 196.6 197.3, 346.3, 426.9,_431.8, 455.1, 464.8, 653.9, 684.7, 777.6, 882.0, 911.4, 995.7, 1112.7, 1163.0 208.7 196.6, 431.8, 728.3 315.4 728.3, 882.0 324.6 108.9, 403.8 346.3 197.3, 381.3, 822.0 381.3 206.6, 426.9, 455.1, 639.0, 882.0, 1112.7 403.8 108.9, 324.6, 728.3 426.9 206.6, 381.3, 455.1, 639.0, 1020.3, 1112.7 431.8 196.6, 346.3, 381.3, 426.9 684.7, 882.0 455.1 381.1, 426.9, 639.0, 728.3 464.8 197.3, 728.3, 882.0 628.6 --- 639.0 197.3, 381.3, 455.1, 882.0 653.9 196.6, 777.6 684.7 197.3, 381.3, 639.0, 702.1, 785.3 702.1 684.7 728.3a 108.9, 197.3, 315.4, 464.8, 882.0 777.6 196.6, 653.9, 995.7 785.3 684.7 882.0 196.6, 315.4, 381.3, 431.8, 464.8 639.0, 728.3, 1020.3, 1112.7 69 Table 5-4. (cont'd.). Gated y-Ray (keV) Coincident y-Rays (keV) 911.4 196.6, 990.8 990.8 196.6, 911.4 1020.3 882.0 1112.7 197.3, 381.3, 882.0 1163.0 196.6 aThere are two transitions with this energy in the level scheme. 70 expected them to be isotropic due to deexcitation from the 628.6-keV isomeric state. The angular distribution coefficients not listed in the table were either part of unresolvable multiplets or too weak for accurate peak fitting. These coefficients were then compared to theore- tical values [Ya67] to aid in assigning spins. The values of A2/A0 were, in general, more reliable than the values of Aule and could be used to estimate the mixing ratios for the more intense transitions. The data with the fitted curves for some of the y-rays are shown in Appendix F. 5.3. Construct of the 1”1Pm Level Scheme and Comparison The proposed level schemes for lule, both from (p,2ny) and (u,4ny) reactions, were constructed based primarily on the coincidence informa- tion, intensity balances, conversion coefficients and delayed-coincidence spectra [in the case of (0,4n7) reaction]. Secondary factors were energy_ summing relationships,input from the known 1415mm+g decay scheme [Ep72, Ke77], and angular distribution data from this study. The spin and parity assignments were made on the basis of angular distribution coefficients, conversion coefficients, and input from the 1“18mm+g decay scheme. This section will be broken into three parts: 1) level scheme and spin~parity assignments from (p,2ny) reaction, 2) level scheme and spin- parity assignments from (0,4ny) reaction, and 3) comparison between these two reactions and with other experimental results. 5.3.1. Level Scheme and Spin-Parity Assignments from (p,2ny) Reaction The resulting level scheme from (p,2ny) reaction is shown in Figure 5-6. Specific details of construction of the level scheme and JTr assign- ments are discussed next. 71 .CCwuummu A>:m.mv 509w nmcwmuno Emflsa u: mamsom Hm>oq 00 .0 8&2: ludfia g % m.~-om-x3w$ .oum muswam 72 Ground, 196.6-, and 628.6-keV States The most intense y transition in the in-beam as well as the off- line experiments is l96.6-keV transition, which is in coincidence with the 431.8-keV transition (and with others -cf. Table 5-2). 0n the other hand, no other y-rays appear to be in coincidence with the 431.8-keV (except 208.7-keV transition which is visibly weak — see 431.8-keV gates in Appendix C). This leads to the adoption of a first excited state at 196.6-keV. This is completely consistent with the systematics of this region, and placement of the 628.6-keV state which decays to the 196.6- keV level via the 431.8-keV transition and to the ground state via the 628.6-keV transition also results. The J" of the ground state of 1“P111 is known to be 5/2+ [Ya75 and Ec72], and the 196.6- and 628.6-keV states have been assigned 7/2+ and 11/2', respectively, on the basis of the multipolarities of the 196.6- and 431.8-keV transitions and logft values for 1”18mm B-decay. The half-life of 628.6-keV state was measured by several people. The latest measurement was 0.59 nsec [Ke77]. In this work, the half-life of this isomeric state has been measured from (0,4ny) reaction to be 0.63 usec - cf. section 5.3.2. Because of the isomeric nature of the 628.6-keV state, one expects the 196.6-, 431.8-, and 628.6-keV transitions to be definitely isotropic. In fact, this was proven from both (p,2nY) and (0,4ny) to be true (e.g. see the values of A2 and A“ for the 196.6- and 628.6-keV transitions in Table S-l). Although this information does not allow us to comment further on the J" assignments, it is conceivable to believe J7T assignments from ll”Sm“ B-decay both by the systematics of the region and by the fact of the long half-life of the 628.6-keV state are reasonable. 73 403.8-; 438.8-, and 728.3-keV States These states are the other low-lying and presumably lower spin states. The fact that 438.8-keV transition is not in coincidence with any transition leads to the placement of a level at 438.8 keV. This level has been reported to have J1r - 1/2+ with some feeding from the many higher-lying,lower-spin states [Ke77]. Therefore, it is not unusual not to see these low-spin states at such a high excitation energy in (p,2ny) reaction. Spin assignment for 438.8—keV state was not possible from angular distribution coefficients because of their large errors. However, J1T 8 1/2+ assignment,on the basis of the multipolarity and the logft value for 1”18mg B-decay, seems to be appropriate considering both the shell model and nuclear systematics. Also, absence of any transitions in coincidence with 438.8-keV transition in (p,2nY) reaction is another evidence for this spin assignment. From the 403.8-keV gated spectrum (which includes 402.6-keV gate as well) shown in Appendix C,one can see evidence for coincidences with the 324.4- and 749.6-keV transitions (the rest of the y-rays are in coinci- dence with 402.6-keV transition). The intensity balances suggest levels at 403.8 , 728.3 , and 1153a3keV. The 403.8-keV transition is a mixed Ml/EZ transition; therefore the JTr assignment is restricted to 3/2+, 5/2+, or 7/2+. The 5/2+ value is ruled out because of the large negative value of A2 and the small posi- tive value of A“. The logft of 5.8 for this level from 1HSmgdecay and the missing transition from this level to the 7/2+ level at 196.6 keV, rule out J1T = 7/2+. Thus, 403.8-keV state has J1T a 3/2+. The 728.3-keV state feeds into the 5/2+ ground, 7/2+ 196.6-, and 3/2+ 403.8—keV states by the 728.3-, 531.3- and 324.6-keV transitions, 74 respectively. From 11+18mg decay, M1 or £2_multipolarity was assigned for the 324.6-keV transition. Our data is consistent with almost pure M1 multi- polarity which limits J1r for 728.3-keV state to l/2+, 3/2+, or 5/2+. The 3/2+ value is ruled out because of the negative value of A2 and the small positive value of A“. On the other hand, the lack of a long half-life for this state rules out the possibility of M3 multipolarity for $31.3- keV transition and therefore‘J1T - 1/2+ can be ruled out. The angular distribution coefficients for this transition give more support to elimi- nate 1/2+ assignment (any transitions deexcite from l/2+ should be iso- trOpic), and to accept S/2+. Also, logft of 6.8 for 728.3-keV state from 1“18m9 decay is consistent with 5/2+ assignment. 804.5-kev State The coincidence information between 607.9- and 196.6-keV y's places this state. It was also seen in ll+1Sm.” decay, where it was tentatively assigned 9/2+ or ll/2+. With the ll/Z+ assignment, the 607.9-keV transi- tion would be pure 32 and with the 9/2"’ assigmnent 1: would be mixed M1/E2. The angular distribution coefficients, even with such large errors, prefer 9/2+. 837.1-keV State This state was placed by coincidence information from its deexciting 208.7- and 640.5-keV transition as well as by its energy sum relationships. The angular distribution coefficients of 837.1—keV transition that deexcites this state to the 5/2+ ground state limits its J1r to 1/2+ or 9/2+. From the 1“18mm decay data, 1/2+ can be excluded. Also, the deexcitations of 640.5- and 208.7-keV transitions into 196.6- and 628.6-keV states do not confirm a 1/2+ assignment. Thus, the 837.1-keV state has J7r = 9/2+. 75 974.2-keV State The coincidence information between the 196.6- and 777.6-keV [second strongest transition in (p,2ny) reaction] y's places this state. The 777.6-keV transition was reported to have El or 32 multipolarity. The angular distribution coefficients are consistent with a stretched £2 transition which limits its J1T to 3/2+ or ll/2+. From 1“Sum decay, spin 3/2+ can clearly be ruled out, leaving J1r t ll/2+ for this state. It is not hard to believe the tentative 9/2+ assignments reached from 1515a? decay data to be incorrect because the negative};1+ value rules out a mixed M1/E2 multipolarity for the 777.6-keV transition. Also, Eppley's et al. argument about 974.2-keV transition to ground state (this transition has not been seen in in-beam) in order to eliminate 11/2+ assignment, is a very poor argument. 1108.0-keV State Again, coincidence relationships between 196.6- and 911.4-keV transi- tions places this state at 1108.0 keV. The small positive value A2 and the large positive value of A“ for 911.4-keV transition, are consis- tent with J + l to J pure 32 transition which restricted the J1r assign- ment to 5/2+ or 9/2+. The 5/2+ value can be ruled out because the (p,2ny) reaction is not likely to populate low-spin states at higher excitation energies. From the 1“15mm decay data we can also exclude 5/2+. There- fore, J1r for the 1108.0-keV state would be 7/2+ 1153.3-keV State This state has been placed on the basis of coincidence information and energy sums of 524.9-, 749.6-, 956.5-, and 1153.3-keV transitions (not seen in 1”1311194“ decay). These deexcitations restricted the JTr 76 + . of this state to 7/2 which is also consistent with angular distribution coefficients of 956.5- and 1153.3-keV transitions. 1167.1-keV State This state feeds into the 11/2- 628.6-keV state by the 538.5-keV transition (although the long half-life of the 628.6-keV state makes‘ this impossible to confirm by a direct coincidence measurement, the other coincidence relations with the 538.5-keV confirm this placement as did the extensive coincidence relations from 1“18mm B-decay). If the 538.5-keV transition is a M1 transition (Table 5-1), the J1r assignment is restricted to 9/2', 11/2', or 13/2'. The ll/Z' value is ruled out because of the large negative value of A2 and the small positive value of A The fact that this state is not fed by y-rays from a high-spin state 1+. indicates that it most likely is not in the yrast sequence, eliminating J" = 13/2' (below we shall show that the 1313.3-keV state has J" - 13/2' and receives feeding from the high-spin states). Thus, the 1167.1-keV state has JTr - 9/2‘. 1242.5-keV State The coincidence relationships between 196.6- and 1045.9-keV transi- tions and also the 1242.5-keV cross—over transition place this level at 1242.5-keV (not seen in 1”1Smg+m decay). The J"T of this state is restricted to 3/2i, 7/2i, or ll/Zi because of the angular distribution of the 1045.9- and 1242.5-keV transitions (whose multipolarities have not been determined). The 3/Zi value can be ruled out because the (p.2ny) reaction is not likely to populate low-spin states at higher excitation energies. The fact that this state has not been observed in the (a,4ny) reaction and has a large negative value of A“ for the 1045.9-keV transition, 77 n i w + ' rule out J a ll/2 , leaving J = 7/2‘ for this state. A.7/2' assign- ment would require the 1045.9- and 1242.5-keV transitions to be a mixed El/MZ, and although this cannot be definitely ruled out, the 7/2+ assign- ment is most likely preferable. 1313.3-keV State Again, the long half-life of the 628.6-keV state prevents a direct coincidence measurement to place the 1313.3-keV level feeding into it, but the five other transitions seen in coincidence with the 684.7-keV transition place the 1313.3-keV level quite securely. The 684.7-keV transition is reported to have M1 or E? multipolarity [Ke77]. The angu- lar distribution coefficients are consistent with a mixed MllEz transi- tion. A large negative value of A2 and small positive value of A“ restrict the JTr to 9/2‘ or 13/2‘. Since the 684.7-keV transition is seen so intensely in both (p,2ny) and (0,4ny) reactions, yrast arguments lead us to prefer the higher spin, i.e., 13/2‘ for this state. 1359.6ekeV State This state has not been seen in B-decay. The angular distribution coefficients for the 1163.0-keV transition restricted its JTr to‘7/2t or ll/Zi. The small positive A2 and the large negative A“ are more likely consis- tent with J + 2 to J stretched £2 transition. An ll/Z’ assignment would require the 1163.0-keV transition to be M2, and, although this cannot be definitely ruled out, one would prefer the 11/2+ assignment. 1414.5-keV State The coincidence relationships between 538.5- and 247.4-keV transition and 785.3-keV energy sum places this level at 1414.54keV. The JTr of this state is restricted to 11/2“ or 9/2' because of the angular distribution 78 coefficients of the transitions deexciting from this level. 151 0. 6-keV State This state has been observed both by (p,2nY) and (0,4n7) reactions (not seen in B-decay). The angular distribution pattern of 882.0-keV transition, deexciting from this state, is consistent with a stretched E? and restricts the J1r value of the state to 7/2’ or 15/2'. Yrast con- siderations lead us to prefer the larger value of 15/2‘. Other States The remaining states in the level scheme in Fig. 5-6 were placed on the basis of coincidence data, corroborated by B-decay data. Their J1r values could not be determined uniquely from our present experimental data; however, some JJr values could be excluded on the basis of angular distribution coefficients and the first spin assignments are more pro~ bable. Also, some of these states observed in (p,2ny) reaction had their assignments made from 1“Slum-W decay —- these are indicated by asterisks on the level scheme. It is worth mentioning that there are two 728.3-keV and two 785.3-keV transitions in the level scheme. 5.3.2. Level Scheme and Spin-Parity Assignments from (0,4ny) Reaction The proposed level scheme from (0,4n7) reaction is shown in Figure 5-7. The intensities are normalized to 100 for the 431.8-keV transition strength. It should be mentioned here that this transition is part of a doublet (there is a 433.7-keV transition coming from 1“2Pm). In the level scheme there are also more y-ray intensities going into the 628.6-keV state than coming out (about 11% more). Finally, the placement of those states (12 states) that depopulate directly or indirectly into the 628.6-keV isomeric state is based on the 79 .:0wuummu A>:q.cv Scum nocfimuno Em~:~ mo mausom Hm>mq 0m .0 Can—:1 h.~:°.ux3ml .anm muamae -80 delayed coincidence spectrum as well as prompt coincidence spectra. The 431.8-keV delayed gate (shown in Figure 5-8) enhances those transitions that feed into the 628.6-keV state (t - 0.63 nsec) in lule. To 1/2 obtain this spectrum, the Xraxis was gated on the 431.8-keV transition and time-axis was gated on the proper side of the TAC spectrum. Specific details of construction of the level scheme and JN assign- ments are discussed below. Ground, 196.6-, and 628.6-keV States Again, the most intense Y transition in (0,4n7) reaction as well as the (p,2nY) reaction and off-line experiments is 196.6-keV transition. Its coincidence relationship with 431.8-keV and energy sums place the first excited state at 196.6-keV and the isomeric state at 628.6 keV. The latter decays to the 196.6-keV via the 431.8-keV transition and to the ground state via the 628.6—keV transition. The half-life of this state was measured to be 0.22:0.01 usec by Arl't et al. [Ar70], 0.7:0.02 nsec by Werner et al. [Wa7l], and 0.59:0.02 nsec by Kennedy et a1. [Ke77]. From the coincidence experiment for the (a,4ny) reaction, the half-life of this state could be measured. A FAST- SLOW coincidence system with two Ge(Li) detectors and a Time-To-Amplitude Converter (TAC), were used (c.f. section 5.2.3.). The TAC resolving time was about 21 ~ 4 nsec. The X-axis was gated on the 431.8-keV transition and the Y-axis was gated on the entire spectrum above 4SO-keV. The time spectrum after background subtractions is shown in Figure 5-9. A prompt peak in the time spectrum is due to prompt-coincidences of 433.7-keV y-ray with other transitions in lusz. Using the computer code KINFIT [Dy7l], the half-life for the 628.6-keV state turned out to be 0.63:0.02 nsec. 81 noon menu muowuumcouu omosu moocmnco anuuoodm mane 00.0w .am~:A ca atom: me.o u ~\Hpv oumum >ox|o.m~c onu one“ mauoowfincfi no hauooufin mum—>52 .52qu0 00a. . 000. _ . . _ 1‘ 1‘ _ 8 . .c. w .v/ «n \ .uumy_7o n: ,_. .-w a a _ a 9 m ... w o .2 200 33.00 >mxum..m¢ .aauuoodm oucmpaocuoo vohcaon 00m. a 2'99'2" V'QIE' 6'90? - .mnn «names EZGI— l O K) "IBNNVHD 83d SiNflOD 00. 00. 00m COUNTS PER CHANNEL 82 I04 3- '0 1.90.63t0.02p.5 '7 ’2 10° J. I. I 2 3 4 TIME (#5) Figure 5-9. Time axis projection on a semi-logarithmic plot illustrating the half-life of 628.6-keV state in lklpm' 83 As mentioned in section 5.3.1., because of the isomeric nature of the 628.6-keV state, the 196.6-, 431.8-, and 628.6-keV transitions are isotropic. In fact, this was proven from (0,4ny) reaction to be true (e.g. see the values of A2 and A“ for these transitions in Table 5-3). Therefore, J” assignments for 196.6- and 628.6-keV states are not possible. From 1“8111’” B-decay, the J“ for the ground-, 196.6-, and 628.6-keV states were assigned to be 5/2+, 7/2+ and 11/2', respectively. It is conceivable to believe these J" assignments, both by the systematics of the region and by the fact of the long half-life of the 628.6-keV state, are rea- sonable. 403.8- and 728.3-keV States The other set of low-lying states has the interconnecting transitions of 324.6-, 403.8-, and 728.3-keV. Coincidence relations between 324.6- and 403.8-keV transition, and 728.3-keV energy sum lead to the placement of levels at 403.8 and 728.3 keV. Because the 403.8-keV transition was seen as weak in (0,4n7) reaction, the angular distribution coefficients could not be measured for this tran- sition. Therefore, the J1r a 3/2+ assignment from (p,2ny) reaction (dis- cussed in section 5.3.1.) was adopted for 403.8-keV state. The 324.6-keV transition deexciting from 728.3-keV state is reported [Ke77] to have M1 or E2 multipolarity. Our data is consistent with an almost pure Ml which limits J17 for 728.3-keV state to l/2+, 3/2+, or 5/2+. By using the same arguments as the (p,2ny) reaction, the 1/2+ and 3/2+ assignments can be ruled out, leaving J7T = 5/2+ for this state. 837.1-keV State This state has been seen in the (p,2ny) reaction, but 108.9—keV 'transition from this state into 728.3-keV state is missing in the (p,2ny) 84 reaction. Instead, the 640.5-keV transition from this state into the 196.6-keV state has been observed in the-(p,2ny) reaction and not seen in the (0,4n7) reaction. The angular distribution coefficients are consistent with the J1r s 9/2+ assignment discussed in section 5.3.1. 974.2-, 1108.0-, 1313.3-, 1359.6-, 1510.6-, 1628.1- 1969.9-, 2015.4-, 2098.8, and 2238.9-keV States These are other states which have also been observed in the (p,2ny) reaction. Generally, the placement of these states are based on the coincidence information, delayed-coincidence spectrum, intensity balances, and energy summing relationships supported by both (p,2ny) and (a,4ny) reactions. The J1r assignments for these states were made on the basis of angu- lar distribution coefficients and transition multipolarities. Where there was a large error in the A2 or AL+ values in one case, the values from the other case were chosen. Some other states which have not been seen in the (p,2ny) reaction will be discussed next. 1055.5-keV State The coincidence relationships between 426.9- and 455.1-keV transitions, intensity balance, and the 882.0-keV energy sum lead us to place a level at 1055.5-keV. The angular distribution coefficients for 426.9- and 455.1-keV y's restricted the JTr of this state to 11/2‘ or 13/2‘. The fact that this state is not fed by y-rays from high-spin state indicates that it most likely is not in the graSt sequence, eliminating JTr = 13/2" (as discussed“ in section 5.3.1. The 1313.3-keV state has 3“ 13/2‘ and receives feeding 85 from the high-spin states). Thus, the 1055.5-keV state has J1r - 11/2‘. 1891.95! 2530.9-, 2554.3-, 2703.7-, and 3004.6-keV States These states are the high-lying and higher spin states which are seen only in the (o,4ny) reaction. The tentative J1| assignments made for these states are based on the 52 and A“ values of transitions deexciting from them. Except for 1891.9- keV state, no unique JJr assignment was possible. The 2530.9-keV state has a specific significance. The fact that the 639.0- and 1020.3-keV transitions deexciting from this level have an isoe tropic nature (see Table 5-3 for their A2 and A“ values) and no-y-rays seen feeding to this level, would lead us to believe that this is most likely an isomeric state. The half-life measurement for this state was not possible from the (a,4ny) coincidence data, but estimated to be more than 2 nsec. . 5.3.3. Comparison Between the (p.2ny) and (a,4ny) Reaction and with other Experimental Results States in lkle deduced from the present work are compared with the ll+1Smm'"? 8+/EC decay [Ep72, K277] in Figure 5-10. Levels in columns 1 and 2 are based on the (p,2ny) and (a,4ny) reactions reported here while levels in column 3 are from s-decay. The state at 1055.5~keV as seen in the (a,4ny) reaction by no means is identical with the 1046.4-keV state observed in B-decay. Many high-spin states have been observed from the (a,4ny) reaction not seen in B-decay or the (p,2ny) reaction as one expects due to higher angular momentum transfer by alpha particles. Also, a num- ber of levels exist which were populated in one or two of the three types of experiments. 86 Figure 5-10. Energy levels of lule. Levels in columns 1 and 2 are from present work while levels in column 3 are from B-decay. Spins are shown in 2J. 3.0 2.5 N 0 Excitation Energy (MeV) 0.5 0.0 87 l9‘,|5' l3',l7' l5', I l' "'-'-:N.Qv eouu seem. es Anon: e.~ a N\~ev sense >oxue.mae sen een loose em 1 ~\le. ooson >ox1o.-m sen Ceca too“ easy mcoauumcotu smog» assesses asuuomdm mash .aauuoodm mococaocfioo vo>mamn .mn::;. .mccoeu OOON 000. O 8 9 .11 nhv AHV . q/v .hv mmwnkv q/u ./ mjb hH.mmm .1. .1.Anv n0. 11. n». .hv u...nv .0 O 7.01 . Z 1. .l . .9 n». .11 .1e nu. nHv PI.IL r AHV no 960 8.8.2. >mx-m.m: - p 9'92? 09172 V'GIZ I'66l .I. momnoonxzmi 00. 0mm .Nuo seamen 10003 0) 18d Iauuoqg 99 Table 6-2. Summary of coincidence results for the lL‘°Ce(p,2ny)1391’r reaction. Gated y-Ray (keV) Coincident y-Rays (keV) 92.9 113.9, 738.1, 982.3 113.9 219.4, 246.0, 336.6, 475.5, 698.3 701.1, 708.1, 732.4, 738.1, 900.2, 910.1, 982.3, 1014.7, 1075.2, 1089.5 179.7 219.4, 246.0, 900.2 184.3 405.2, 512.0 199.1 219.4, 701.1 219.4 113.9, 179.7, 199.1, 246.0, 336.6, 701.1, 708.1, 822.0, 900.2 246.0 113.9, 179.7, 219.4, 708.1, 900.2 254.8 219.4, 547.7 302.6 113.9, 600.5, 802.5, 910.1 336.6 219.4, 900.2 405.2a 184.3, 512.0, 670.9, 802.5 418.5 113.9, 701.1, 708.1 475.5 113.9 547.7 113.9, 254.8, 302.6, 708.1 589.4 --- 600.5 113.9, 405.2, 910.1 622.3 113.9, 809.5, 910.1 670.9 405.2, 802.5 698.3 113.9, 219.4, 910.1 701.1 113.9, 199.1, 219.4, 246.0, 708.1 708.1 113.9, 219.4, 246.0, 254.8, 336.6, 547.7, 701.1, 802.5, 900.2, 1105.2 100 Table 6-2. (cont'd.). Gated y-Ray (keV) Coincident y-Rays (keV) 732.4 113.9, 738.1 738.1 113.9, 732.4, 982.3, 1014.7, 1075.2, 1089.5 796.6 827.8 802.5 113.9, 302.6, 405.2, 708.1 809.5 113.9, 622.3, 910.1 822.0 -- 827.8 796.6, 962.6 900.2 113.9, 179.7, 219.4, 246.0, 336.6, 708.1 910.1 113.9, 219.4, 600.5, 622.3 698.3, 809.5 962.6 827.8 982.3 113.9, 738.1 1014.7 113.9, 738.1 1075.2 113.9, 738.1 1089.5 113.9, 738.1 1105.2 113.9, 708.1 1369.7 -- aThere are two transitions with this energy in the level scheme. 101 6.2.. Experimental Details and Results for (0,4ny) Reaction 6.2.1. Target and Reaction The states in 139Pr were excited by the 139La(01,4ny)139Pr reaction. A target was prepared by drying a thin slurry of 99.9% enriched 139La203 onto a thin formvar backing. The reaction cross sections for (o,xn) reactions as a function of alpha particle energy were calculated using the code CSBN [CS8N]. The optimum alpha particle energy for the (6,4n7) reaction in order to minimize the production of the Y-rays is 50 nev. At this energy, the amount of contaminant production (0,3n) and (a, 5:0 is about 4% of the total cross section. The highest energy alpha beam, 47 MeV, which could be obtained by the MSU cyclotron was used for the 139Pr experiments. The amount of the main contaminant 170 Pr at this energy is going to be about 14% of the total cross section. The contaminants encountered in this study were 1“Pr, ll+oPr, 17°Ce, 139Ce, 138Ce, and 139La. In addition, 18F and 29? lines coming from oxide in the target and also 27Al lines were present in all spectra. 6.2.2. Y—Ray Singles Spectra The 139Pr singles Y-ray spectra taken with a 7.7Z-efficient Ge(Li) detector had a resolution of 1.9 keV FWHM. This detector was placed at 125° with respect to the beam direction. Typically, a beam current of =10 na was used and the detector was placed 20 cm from the target, resulting in a counting rate of 86000-8000 cps. A singles Y-ray spectrum taken over a 2.5-h period is shown in Figure 6-3. The energy calibrations of the Y-ray transitions were performed using well-known radioactivities, 60 e.g. Co, 152 6 Eu, and 22 Ra. Transition intensities were determined by 102 “SD! ~00-2l4 Singles Speciro o’r |25° l39pr 0.5 memo . moon. . some! 0 . 1h .eme11. 1 _o:: odme o «31 en. 0 meme mm. 11 3.1111 .m mace . 2 9mm» N.oom.m_\flo_m, o . m I m smegma/I one . w 9081111 :8 m \ 3 0.3? .< 09.. 00 NN/ . mn_l1ll1lm.mm~1 msmm/ comm , odmm . x 003.1 en._e_\ _. o. m 36 003111 . o .6. 0 some! 33 . meem .0 eo.~l11111111 . 5 some] amen 8: %%%~ _.m2.\ w . \\\\\ emos - - so: .9311 /.osuo.-m see 00:“ team umnu meoauwmcmuu omozu massages Enuuoodm was? 000m L'OQEI— Eco .mpEzz 35.9.0 09860 P >mx-..m0N .Esuuomdm ooconwocco cmxmamn OOON ooo. . ; 1.7.2.44: ....34..-...11...233213533..4141]-.. _ x . Po 1. 9 9 v W 6 m 0 t v Z nhu “la ”1. mu. n». .hv . 0 6 Ce .9 8 .O t Z 9 .9 O _/ 2_ q/u ..9 n».nnu by. .9 ./.. 9 1|}. \\ men . 1}. q/u_/u emu tho 92.0 099 .m 6 av :N1001x3m2 .mie shaman oo. n10 .ooN O nu m. 3 .00m .mu m -oon nlu nu. nu -oomw no. 110 Table 6-4. Summary of coincidence results for the 139La(01,4ny)139Pr reaction. Gated Y-Ray (keV) Coincident y—Rays (keV) 60.2 200.3, 219.4, 244.5, 444.6, 819.7, 900.2 113.9 179.7, 199.1, 200.3, 214.0, 219.4, 244.5, 246.0, 260.0, 326.0, 336.6, 402.8, 418.5, 436.0, 444.6, 454.1, 543.3, 558.2, 633.6, 701.1, 708.1, 738.1, 819.7, 900.2, 910.1, 1014.7, 1330.7 128.0 200.3, 219.4, 244.5, 326.0, 336.6, 345.0, 436.0, 543.3, 605.9, 900.2 179.7 113.9, 199.1, 200.3, 219.4, 244.5, 246.0, 280.0, 326.0, 336.6, 354.8, 382.8, 402.8, 418.5, 436.0, 444.6, 451.1, 465.3, 558.2, 618.5, 701.1, 708.1, 738.1, 900.2, 1330.7 182.5 179.7, 200.3, 219.4, 246.0, 280.0, 336.6, 454.1, 543.3, 708.1, 822.0, 900.2, 1173.4 (199.1+200.3) 60.2, 113.9, 128.0, 199.1, 200:3, 214.0, 244.5, 246.0, 280.0, 326.0, 336.6, 345.0, 382.8, 436.0, 454.1, 543.3, 558.2, 609.5, 701.1, 708.1, 738.1, 786.7, 819.7, 900.2 214.0 182.5, 200.3, 219.4, 246.0, 280.0, 336.6, 543.3, 819.7, 900.2 219.4 60.2, 113.9, 179.7, 182.5, 199.1, 200.3, 214.0, 244.5, 246.0, 260.0, 280.0, 293.9, 326.0, 336.6, 345.0, 354.8, 402.8, 436.0, 444.6, 454.1, 543.3, 558.2, 605.9, 618.5, 633.6, 701.1, 708.1, 786.7, 819.7, 900.2, 1330.7 ~ 244.5 179.7, 200.3, 219. 436.0, 543.3, 708. 246.0, 326.0, 336.6, , 786.7, 819.7, 900.2 #1:- U 199.1, 200.3, 214.0, 280.0, 293.9, 326.0, 436.0, 444.6, 454.1, , 701.1, 708.1, 786.7, ‘0 246.0 113.9, 179.7, 182. 219.4, 244.5, 260. 336.6, 402.8, 418. 543.3, 618.5, 633. 900.2, 1330.7 O GUOU'I to 260.0 113.9, 179.7, 219.4, 293.9, 708.1 111 Table 6-4. (cont'd.). Gated Y-Ray (keV) Coincident y-Rays (keV) 280.0 182.5, 200.3, 214.0, 219.0, 336.6, 543.3 293.9 113.9, 219.4, 246.0, 260.0, 708.1, 786.7, 900.2 326.0 48.0, 113.9, 128.0, 179.7, 200.3, 219.4, 246.0, 336.6, 402.8, 436.0, 444.6, 543.3, 708.1, 786.7, 900.2, 1330.7 336.6 113.9, 128.0, 179.7, 182.5, 199.1, 200.3, 214.0, 219.4, 244.5, 246.0, 280.0, 326.0, 436.0, 444.6, 543.3, 701.1, 708.1, 738.1, 786.7, 900.2 345.0 200.3, 219.4, 336.6, 543.3, 605.9, 900.2 354.8 113.9, 179.7, 219.4, 246.0, 708.1, 900.2 1330.7 402.8 113.9, 179.7, 219.4, 246.0, 326.0, 436.0, 708.1, 900.2, 1330.7 418.5 113.9, 200.3, 246.0, 336.6, 444.6, 543.3, 701.1, 708.1 425.6 113.9, 199.1, 219.4, 701.1, 708.1, 900.2 436.0 48.0, 60.2, 113.9, 128.0, 179.7, 200.3, 219.4, 244.5, 246.0, 326.0, 336.6, 402.8, 418.5, 444.6, 543.3, 701.1, 708.1, 786.7, 900.2, 1330.7 444.6 60.2, 113.9, 219.4, 336.6, 543.3, 708.1, 786.7, 900.2 454.1 113.9, 179.7, 182.5, 200.3, 219.4, 246.0, 708.1, 900.2 527.6 179.7, 246.0, 336.6 543.3 113.9, 128.0, 182.5, 200.3, 219.4, 244.5, 280.0, 326.0, 336.6, 418.5, 436.0, 444.6, 558.2, 605.9, 708.1, 786.7, 900.2 558.2 60.2, 113.9, 179.7, 200.3, 219.4, 246.0, 336.6, 543.3, 708.1, 819.7, 900.2 Table 6-4. (cont'd.). 112 Gated y-Ray (keV) Coincident y-Rays (keV) 592.9 605.9 618.5 633.6 701.1 708.1 738.1 786.7 819.7 822.0 827.8 900.2 910.1 1010.1 1014.7 1173.4 1330.7 113.9, 179.7, 246.0, 336.6, 708.1 60.2, 113.9, 128.0, 200.3, 219.4, 336.6, 345.0, 113.9, 113.9, 418.5, 402.8, 900.2, 113.9, 543.3, 219.4, 200.3, 708.1, 246.0, 219.4, 179.7, 199.1, 708.1 179.7, 418.5, 1330.7 336.6, 1014.7 219.4, 436.0, 900.2 900.2 246.0, 219.4, 246.0, 543.3, 708.1, 900.2 246.0, 336.6, 326.0, 336.6, 701.1, 819.7, 48.0, 113.9, 200.3, 219.4, 244.5, 246.0, 326.0, 336.6, 436.0, 444.6, 543.3, 708.1, 819.7, 900.2 60.2, 113.9, 182.5, 200.3, 219.4, 244.5, 444.6, 708.1, 900.2 48.0, 60.2, 113.9, 128.0, 179.7, 200.3, 219.4, 244.5, 246.0, 260.0, 293.9, 326.0, 336.6, 345.0, 402.8, 708.1, 786.7, 819.7, 113.9 113.9 74.9, 113.9, 738.1 113.9, 179.7, 182.5, 336.6, 543.3, 708.1, 113.9, 179.7, 219.4, 436.0, 708.1, 900.2 436.0, 1330.7 200.3, 900.2 246.0, 444.6, 543.3, 219.4, 246.0 326.0, 402.8, 113 6.3. Construct of the 139Pr Level Scheme and Comparison The proposed level schemes for 139Pr, both from (p,2ny) and (a,4ny) reactions, are supported primarily by coincidence information, intensity balances, and delayed-coincidence spectra; and secondly by angular distribution data, energy summing relationships and from known 139Nd’m'g decay scheme [Be69, Bu7l]. The spin values and parities given in both level schemes were derived from the angular distribution coefficients, conversion coefficients, ratios of y-ray intensities in the proton and alpha induced reactions, and input from the 139Ndm+g decay scheme. This section will be broken into three parts: 1) level scheme and spin-parity assignments from the (p,2ny) reaction, 2) level scheme and spin-parity assignments from the (a,4nv) reaction, and 3) comparison between these two reactions and with other experimental results. 6.3.1. Level Scheme and Spin-Parity Assignments from (p,2ny) Reaction In Figure 6-6, the level scheme of 139Pr obtained from the (p,2ny) reaction is given. Specific details of the construction of the level n scheme and J assignments are discussed next. Ground, 113.9-, and 822.0-keV States The large relative intensity of the 113.9-keV transition combined with its coincidence behavior leads to a placement of a first excited state at 113.9 keV. The isomeric state at 822.0 keV was first placed on the basis of prompt-coincidence spectra. It was then confirmed by the delayed-coinci- dence spectrum shown in Figure 6-2. This isomeric state decays to the 113.9-keV level via the 708.1-keV transition and to the ground state via the 822.0-keV transition. 114 .00Huommu A>:N.Qv azu scum cecacuno “mam. mo wemsom H0>04 00 an anmn. .~. - 00- xDmS .oue unease 115 The ground state has been reported to have JTr = 5/2+ [Ep72], and the 113.9- and 822.0-keV states have been assigned 7/2+ and 11/2’ [Be69, Bu71], respectively on the basis of multipolarities of the three above Y transitions and the logft values for 139Ndm B-decay. Also, in the 139Ndm decay studies, the 113.9- and 822.0-keV states were measured to have half-lives of 2.6 and 36 nsec, respectively. In this study, 113.9-, 708.1-, and 822.0-keV transitions were found to be definitely isotropic (e.g. see the values of A2 and An for 113.9- and 822.0-keV transitions in Table 6-1.) Although this infor- mation does not allow us to comment further on the J1r assignments, it is consistent with the half—life of the 822.0-keV state. 4054;;1 589.4-, and 917.1-keV'States The other set of low-lying states, presumably of lower spin, has the interconnecting transitions of 184.3, 405.2, 475-5. and 512.0 keV. Coincidence relations among them and the intensity balances lead to the placement of levels at 405.2, 589.4, and 917.1 keV. These states were also observed in 13‘3ng decay. The 405.2-keV transition is a mixed Ml/EZ transition; therefore, the Jfl assignment is restricted to 3/2+, 5/2+, or 7/2+. The 5/2+ value is ruled out because of the large negative value of A2 and the small positive value of An. The logft of 6.4 for this level from 139ng decay and the missing transition from this state to the 7/2+ level at 113.9 keV, rules out J" - 7/2+. Thus, the 405.2-keV state has J" - 3/2+. The 589.4-keV state feeds into the 5/2+, 7/2+ 113.9-keV, and 3/2+ 405.2-keV states by the 589.4—, 475.5-, and 184.3-keV transitions, respectively. From 133ng decay, M1 or £2 multipolarity was assigned for the 184.3-keV transition. The A2 and A,+ values for this transition 116 are consistent with the M1 multipolarity. The.angular distribution coefficients of transitions deexciting from this level limit its J1r to 3/2+ or 5/2". The 917.1-keV state feeds into the 5/2+ ground state by the 917.1—keV transition and most probably into the 3/2+ 405.2-keV state by the 512.0- keV transition. The angular distribution coefficients for the 917.1- keV transition limit its J1r to 3/2+ or 7/2+. From 139Nd9 decay, 7/2+ can clearly be ruled out (logft ‘ 6.6), leaving J1r a 3/2+ for this state . 827.8-keV'State. The coincidence relationships between 827.8-, 796.6-, and 962.6-keV transitions, and the relative y-ray intensities, place the levels at 827.8, 1624.5, and 1790.4 keV. The 827.8-keV transition that deexcites from 827.8-keV state to the 5/2+ ground state is an £2. The angular distribution data for this transition can be fitted with only two values, 1/2+ or 9/2+. J1r s 1/2+ can be eliminated from the B-decay work; thus, this level has.)1r - 9/2+. 852.0-keV State The coincidence information between the 113.9- and 738.1-keV [third strongest peak in the (p,2ny) reaction] Y's places this state. The 738.1- keV transition was reported to have 22 +.M1 multipolarity. The angular distribution coefficients are consistent with a stretched E2 transition which restricts its J" to 3/2+ or 11/2+. Again from 139Ndm decay, spin 3/2+ can be ruled out, leaving JIr = 11/2+ for this state. The tentative 9/2+ assignments reached from B-decay data by Beery et al. [Be69] are believed to be incorrect because the negative Au value rules out a mixed M1/EZ multipolarity for the 738.1-keV transition. Also, their argument regarding the 852.0-keV transition to the ground state is a very poor argu- ment [this transition has not been seen in the (0,4ny) reaction]. 1024.0-keV State This state was placed on the basis of the coincidence relationships between 113.9- and 910.0-keV y-rays. The 910.1-keV transition that deexcites from this state to the 7/2+ 113.9-keV state is an 32 or Ml [Bu7l]. The angular distribution coefficients are consistent with J to J i l 32 + Ml mixed transition which limits the J11 assignment to 5/2+ or 9/2+ for this state. The 5/2+ value can be ruled out because the (p,2ny) reaction is not likely to populate low-spin states at higher excitation energy. From the 1”Ndm decay, 5/2+ can also be included; therefore, J1r for 1024.0-1tev state would be 9/2+. 1369.7-keV State This state feeds into the 11/2' 822.0-keV state by the 547.7-keV transition. If this transition is an M1 transition (Table 6-1), the J1T assignment is restricted to 9/2', 11/2', or 13/2-. The 11/2‘ is ruled out because of the large negative value of A2 and the small positive value of A4- The fact that this state is not fed by v-rays from a high- spin state indicates that it most likely is not in the yrast sequence, thus eliminating J1T - 13/2‘ (below it is shown that the 1523.1-keV state has J1r - 13/2' and receives feeding from the high-spin states). Thus, the 139.7-keV state has JTr 8 9/2’. 1523.1-keV'State The 701.1-keV Y-ray deexciting from this level to an 11/2- 822.0-keV state is reported to have M1 or £2 multipolarity [Bu7l]. The angular 118 distribution coefficients are consistent with a mixed.Ml/EZ transition and restrict the J1r to 9/2' or 13/2‘. Since the 701.1-keV Y-ray is seen so intensely in both (p,2ny) and (a,4ny) reactions, yrast arguments lead us to prefer the higher spin, i.e., 13/2‘, for this state. 1722.2-keVIState This state has been observed both by (p,2ny) and (0,4ny) reactions (not seen in B-decay). The angular distribution coefficients of 199.1- and 900.2-keV B-rays decaying from this state limit its ..7‘r value to 15/2‘. 1941.6-keV State This state is the last state for which unique spin assignments were possible. The angular distribution coefficients of a 219.4-keV transition deexciting from this level to the 15/2‘ 1722.2-keV state are consistent with stretched.Ml or Ml/EZ mixed transitions. The J1r assignment is restricted to 13/2' or 17/2' due to the large negative value of A2 and the small positive value of A“'. Since 219.4-keV Y was seen so intensely in both the (p,ZHY) and (9,4nY) reactions, yrast arguments lead us to prefer the higher spin, i.e., 17/2‘, for this state (which also receives feeding from high-spin states). 1’ Other States The remaining states are not uniquely determined, however some spins could be eliminated on the basis of angular distribution coefficients from the (p,2nY) or (0,4nY) reactions. All of the spins suggested for 1624.5-, 1834.3-, 1866.7-, and 1927.2- keV states in the present work should thus be considered only tentative (the first JTr assignment is preferable). Also, J1r assignments for 2187.6- 119 2278.2-, and 2367.3-keV states will be discussed in section 6.3.2. It should be mentioned here that there are two 405.2-keV transitions in the level scheme which were indicated by asterisks. 6.3.2. Level Scheme and Spin-Parity Assignment for (a,4ny) Reaction The prompt coincidence data as well as the delayed-coincidence spec- trum (Figure 6-5) and intensity balances have been primarily used to construct the tentative level scheme. Secondary factors were energy summing relationships and angular distribution coefficients.. This level scheme, up to 5 MeV excitation, is shown in Figure 6-7.. The use of the LEPS detector as discussed in section 6.2.3. enabled us to identify the low-energy transitions. Many states not seen from the (p,2nY) reaction have been found due to a higher angular momentum transfer of alpha particle. The J" assignments for states below 2 MeV as seen from the (p,2ny) reaction (except for 1124.0- and 1414.9-keV states) are discussed in sec- tion 6.3.1. These assignments were made on the basis of angular distribu- tion coefficients, transitions, multipolarities, and input from 139ng+m data. Where there was a large error in the A2 or A“ values in one case, the values from the other case were chosen. The unique spin assignments for the levels above 2 MeV were not pos- sible. More experiments such as y-ray excitation functions, electron- conversion, and Yeray lifetimes need to be done in order to assign unique J" to these levels. From angular distrubition data of the present work, some spins could be excluded, however, the J" assignments should be con- sidered only tentative. Specific details of J" assignment will be dis- cussed next. The angular distribution coefficients for the 246.0-, 336.6-, and 819.7-keV transitions deexciting from 2187.6-, 2278.2—, and 2761.3-keV 120 .cOHuommu A>:q.ov aoum nocfiauno Mean. 00 season H0>0A on an Limm. SN -00- x33 .auo enemas 121 states, respectively, are consistent with stretched M1 transitions which restricted their J1r to 15/2' or 19/2'. The fact that 246.0 keV deexciting from a 2187.6-keV state has been observed so intensely in the (a,4ny) reaction, and that there are many y-rays feeding to this state from higher- spin states, leads to a preference of 19/2' over 15/2‘ for this level. The levels at 2367.3—, 2481.5-, and 2821.5—keV were assigned 2172' ' or 17/2' based on the angular distribution data of 179.7-, 293.9-, and 543.3-keV transitions, deexciting from them respectively, and are consis- tent with a stretched Ml. Among them, the 2367.3-keV state most likely has J"=21/2' based on the yrast argument. Also, the A2 and A“ values for the 454.1-keV transition deexciting from the 2821.5-keV state are consis- tent with J +'J or J +'J i 2 E2 transition. This.also confirms the J1r assignments for this state. The 200.3—keV transition feeding from the 3021.8-keV state to the 2821.5-keV state has M1 or Ml/EZ multipolarity due to angular distribu- tion coefficients. This restricted the J1r assignments for the 3021.8- keV state to 23/2‘ or 19/2'. Again, yrast consideration would lead to a preference of 23/2‘. Finally, the states at 3266.2“, 3580.0', 3627.7", and 3698.2-keV could be assigned as 25/2‘, 21/2', or 17/2- according to the angular distribution coefficients of transitions decaying from these states. It should be mentioned here that there is also a possibility of a 15/2’ assignment for these states; however one could eliminate the 15/2' assign- ment because it is highly unlikely to observe a lower-spin state at such a high excitation energy. 122 6.3.3. Comparison Between the (p,2ny) and (u,4ny) Reactions and with Other Experimental Results. The two previous major investigations [Be69, Bu71] of the 139Ndm+g B-decay have revealed a wealth of information about the 139Pr excited states, their associated transitions, the spins and parities of these excited states, and especially information about the multipolarities of many of the 139Pr transitions by Butsev et al. [Bu7l]. Unfortunately, only one Scattering reaction producing 139Pr has been reported. Goles et al. [G072] have investigated the 1"’1Pr(p,t)139Pr reaction. In their study, DWBA calculations for two-nucleon pickups were attempted but no spin assignments were made. Many high-spin, high-lying states not viewed previously have been observed in the present in-beam work. Also, in the case of the (0,4ny) reaction, many higher-spin states were p0pulated due to a higher angular momentum transfer of alpha particles. Figure 6-8 shows the comparison between this work and other investi- gations. Levels in columns one and two are based on the (p,2nY) and (0,4nv) reactions reported here, while levels in columns three and four are from B-decay and scattering reaction, respectively. 6.4. Discussion of Level Configurations The states in 139Pr can be classified into three categories: 1) single quasiparticle states, 2) negative-parity collective states, and 3) positive-parity collective states. 6.4.1. Single-quasiparticle States In 139Pr one can expect to see evidence of all the available single- proton states between Z=50 and Z=82. The most clearcut single-quasiparticle Figure 6-8. 123 Energy levels of 139Pr. Levels in columns 1 and 2 are from present work while levels in column 3 are from B-decay [Be69, Bu71] and levels in column 4 are from scattering reaction [0072]. Spins are shown in 2J. Energy (MeV) IEII II’II II II II II II II II II II II II I] II II II II II II II II Excitation 124 MSUX-OO-ZZZ II I r25’,2|’,l7' 25',2l', I7" 25", 2|', I7" 25:21:17“ [111111111l111111111|111111141|111111111l111111111 125 states are those at 0, 113.9, 405.2, and 822.0 keV. The ground state undoubtedly consists primarily of a single d5/2 proton outside a closed 97,2 subshell and the 113.9 keV state simply promotes a g7/2'1 proton state. The retarded Ml transition between them is characteristic of the £~forbid~ den Ml's between the g7/2 and ds/z states in a wide variety of nuclei in this region. The level at 405.2 keV is presumably a single d3/2 proton state. Systematically, this level has been seen at 403.8 keV in lule (c.f. section 5.4.1), but not in ll’3Eu. The 822.0-keV state shows evidence of being a single h11/2 proton outside the closed 97/2 subshell. The M2 transition from this state to the 113.9 keV state is retarded, while the E3 to the ground state is enhanced over single-particle estimates. The position of the 51/2 state is not so clear, but it is probably fragmented and contributes to several states above 1 MeV. 6.4.2. Negative-Parity Collective States The negative-parity collective states in 139Pr are expected to consist primarily of the "bll/Z state coupled to a 138Ce triaxial core. The first 2+ excited state in 138Ce lies at ~790 keV [Sh77]. The low-lying ("hII/Z x 2?) states should be rather pure configura- tions and should be observed at about 1612 keV in 139Pr. The 1369.7—, 1523.1-, and 1722.2-keV states all deexcite through the “hll/Z state and may represent three of the states in the ("h11/2 x 2?) multiplet. The ("411/2 x 2T)9/2- configuration lies at 1369.7 keV. The 1523.1- keV state feeds the 822.0-keV state and presumably has a (1th“,2 x 2T)13/2- configuration. A state at 1722.2 keV is observed to deexcite through the "hll/z state. This state is tentatively assigned as the (trhn/2 x 2?) 15/2‘ configuration. 126 The states corresponding to (uh x 4?) are expected to lie near 11/2, 2648 keV. The ("bll/z x 4T)17/2- configuration was observed experimentally at 1941.6 keV and leaving the other components for the 2187.6— and 2278.2- keV states. Little can be said about the rest of the higher-lying, high-spin states in 139Pr due to the lack of experimental data. On the other hand, triaxial calculations need to be performed in order to assign appropriate configurations to these states. Such calculations should involve the five single-proton states coupled to the 2?, 0T, 2:, 4T, 3:, and other higher spin vibrational states in 138Ce. It should be mentioned here that states at 1624.5, 1834.3, and 1927.2 keV have been described as three-quasiparticle states by Beery et al. [Be69, Mc69]. Finally, the shell model calculation was performed by Muthukrishnan et al. [Mu7l] in order to describe the negative-parity levels in 139Pr. Their calculations are not in sound agreement with the experimental data and that is because the shell model is not an appr0priate model for this region. 6.4.3. Positive-Parity Collective States The positive-parity states can be generated by coupling the ‘mdg/z ' and ng7/2 to the 138Ce core. These states are all expected to give poorer weak-coupling descriptions due to the ease of mixing with nearby positive-parity states. The (ads/2 x 21) states should lie at :790 keV in 139Pr. They should deexcite to the ads/2 ground state by EZ(+M1) transitions. The state at 827.8 keV is presumably the (ads/2 x 2T)9/2+ component and the state at 917.1 keV is probably the ("dS/z x 2T)3/2+ component. No 127 definite spin assignments were made for the 589.4-keV state, however it is not unlikely to assume this level has a (ads/2 x 2T)5/2+ configura. tion. The (flg7/2 x 2?) couplings lead to observable 9/2+ and 11/2+ states in the vicinity of 904 keV which should deexcite through the ngy/z single- particle state through strong 82 transitions. The most likely candidates lie at 1024.0 and 852.0 keV, respectively. CHAPTER VII SYSTEMATICS OF THE ODD-MASS N=80 NUCLEI The positions of known states in odd-mass N=80 isotones are shown in Figure 7-1. The data for 1331, 135Ca, and 137La are from B-decay or a combination of B-decay and inebeam studies and were taken from Refs. [Pa68, H071], [A168, He75], and [Na73, Hen75], respectively. The 139Pr, 1“Pm, and N3Eu data are from the present in-beam work only. Also, in the case of 139Pr, the states above 3 MeV from (a,4nv) reaction are not shown in this figure. Because few reaction studies have been made (no in-beam work in detail) on 1331, 135Ca, and 137La in this region, the levels can be traced for the most part only over three isotones (139Pr, 1“le, and 1“3Eu) with any certainty. The low-lying level spectra in odd-mass N=80 nuclei are expected to be single-quasiparticle states between Z=50 and 2882 closed shells. Here, the available single-particle orbits are 97,2, and d3/2, lying relatively close together, and then, after a gap of ~500-1000 keV, h11/2’ s and 1/2’ d3/2, also relatively close together. These five single-particle states can- not be traced in all of the N=80 isotones (only in the case of lule have all these five states been observed experimentally). The 258.8 keV (3/2+) state in 1”Eu is not the d3/2 single-particle state as discussed in sec- tion 4.2.1. Also, in some of these nuclei the positions of the d3/2 and 51/2 states are not so clear, but they are probably fragmented and contri- bute to several states above 1 MeV. In N=80 isotones there is a change of ground-state spin between 137La and 139Pr. The d3/2 and h11/2 states 128 Figure 7-1. 129 The position of known states in odd-mass N=80 isotones. The data for 133I, 135Cs, and 137La are from B-decay or a combina- tion of B-decay and in-beam studies. The 139Pr, lule, and ll‘3Eu data are from the present in-beam study. The states in 39Pr above 3 MeV from (a,4ny) reaction are not shown in this figure. Also, spins are shown in 2J. 130 N o Energy (MeV) '01 Excitation I ISUX-OO-ZZS 23’ l9' - .. : —— . 19 .'5 __ 1‘ 17‘ .(p,2n7) l2’lfi' "‘ 21'17‘ ‘ (a ,4” y) o— O —I 1, 21'17' I 7 , 21:17‘ 19",21' '9- - a. " '7' 1 113,1151 I 00-14 .. I9- '5- t t ..m . 13317" .719? n 15‘ 11' .1412. ..w-z—fi‘ - ll l9 5 ' 1127* I ‘- \ O_ 3 l'- u “\..L . \ ._ 9‘ . . - —.|5* '3- ‘ \\ _ \ - _ .. \ \‘OL ._ - \ . -—.-.- \ \O%\ \ ‘ _ oJ—\ \ .. H \ \ II: \ \ . o E \ ‘0- : \ \ \ g 15 a \ 7 \ \ . \ . - \ ‘0 '+ ‘0; 7* \—_ ~ * § ". \ ‘4 '+ I'- .O¢ . ‘ I: - "* \ 3+ / 9* \ . \ . '+ / 9’ ° .1 ‘\ _L o——-/ *.. ~. ..+ _ mxix==.==-9 .3: .... .. —- _---—-——- \ + O + :2 \x’..; A + -— / M. I. L. . 3+,5+/ \ d \ 3* ‘ + \ o» \ p — 3+ 5 \\‘ 3+ 0 ' ...-“K" ‘0 00—?3 \ H u: ‘4“ 5+ ' 7" "‘ \ /.._ d \ * ,/ \ fl. - + \ 5 ’ + + 4 ——--—Z—_—--- ‘ ---.o —__o 5 J 135 137 ... 139 141 143 ”Cs 57La 59Pr 6. Pm ssEu 131 decrease in energy with increasing proton number from the 137La through M3Eu. This trend has been observed in odd-mass Nb82 isotones experi- mentally and theoretically [Ta76]. The low-lying negative-parity collective states (9/2‘, 13/2‘, 15/2‘) in this region are assumed to be odd proton coupled to the first 2+ state of the even-neighbor cores. These states decrease in energy with an ' increasing proton number as one goes from 137La through 1”Eu. In fact, this has been observed to be true for first 2+ states in even-even N=80 isotones from the 13“Xe through 1”Sm cores. The higher negative-parity states observed in some of the odd-mass N'80 nuclei are believed to result from single proton states coupled to the OT, 2:, 4T, 3‘, and other higher-spin vibrational states in cores. The calculations need to be done in the case of 139Pr and ll”Pm before a good understanding of the systematic trends of the negative-parity collective states in this region can be obtained. The only positive-parity collective state which can be traced sys- tematically is the first 11/2+ state. Its energy decreases from 1331 to 137La and thereafter increases to 1“Eu. CHAPTER VIII SUMMARY AND CONCLUSIONS In-beam.Y-ray spectroscopy has been used to investigate the behavior of the excited states in 1"'3Eu, 1“Pm, and 139Pr in order to learn more about the systematics in this region. The (p,2ny) reaction was used to populate the states in 1"’3Eu, whereas the states in 1“P111 and 139Pr were p0pulated via both the (p,2ny) and the (a,4ny) reaction. The Ge(Li)-Ge(Li) Y-Y-t coincidence technique used 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 was very useful in the deter- mination of which y-rays were doublets. The combined use of Y-ray angular distributions from the present work and previous conversion electron data and logft values made the unique spin-parity assignments possible for many states in these nuclei and limited the J1r assignments for some other states. The weak-coupling triaxial calculations have been shown to give an excellent quantitative as well as qualitative understanding of the low- lying level structure in 193E“. The calculations for negative-parity states indicate an oblate shape, and those for positive-parity states gave at least a germinal fit. No calculations have been done in the case of 1“Pm and 139Pr, but in both cases the level structures were explained quite satisfactorily in terms of a triaxial weak-coupling model. Although the results reported here produce some new insights into the systematics of the N=80 region, more experimental work (e.g. excitation 132 133 functions, conversion electron data) as well as theoretical calculations (for 1“Pm and 139Pr) are needed before a good understanding of the behavior of the nuclei in this region can be obtained. BIBLIOGRAPHY [ALICE] [A168] [Ar70] [Au72] [Be69] [Bu71] [Da58] [Dy71] [Ec72] [Ek72] [E971] [E972] 134 BIBLIOGRAPHY A 1 Written by M. Blann and F. Plasil, adapted for the MSU Heavy- Ion Laboratory Sigma-7 computer by W. H. Bentley. P. Alexander and J. P. Lau, Nucl. Phys. A121, 612(1968). R. Arl't, G. Beyer, Y. Vanryschuk, V. A. Mbrosov, T. M. Muminov, V. I. Rason, J. Sazynski, H. Faia, H. Strusny, and E. Herrmann, JINR report No. P6-5517, 1970 (unpublished). IIEVENT, a computer code written by Richard Au, MSU Heavy-Ion Laboratory (unpublished). B D. B. Beery, W. H. Kelly, and Wm. C. McHarris, Phys. Rev. 188, 1851(1969). V. S. Butsev, T. Vylov, V. 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Lohken, H. Rebel, and G. Schatz, Gesellschaft fur Kernforschung mbH KFK 1768(1973). W R. A. warner, R. R. Todd, R. E. Eppley, W. H. Kelly and Wm. C. McHarris, Bull. Am. Phys. Soc. 16, 1161(1971). K. Wisshak, A. Hanser, H. Klewe-Nebenius, J. Bushmann, H. Rebel, H. Faust, H. Toki, and A. Fassler, Z. Phys. A 277, 129(1976). 137 Y . [Ya67] T. Yamazaki, Nucl. Data Tables Q, 1(1967). [Ya75] F. Y. Yap, R. R. Todd, W. H. Kelly, Wm. C. McHarris, and R. A. Warner, Phys. Rev. C E, 952(1975). APPENDICES Figure A. 138 APPENDIX A Gated Coincidence Spectra of Transition in 1”Eu. Gated spectra of transitions in lL’3Eu from (p.2ny) reaction. Background subtraction using the adjacent continuum has been included. The spectra are arranged according to increasing energy. Channel C aunts per 139 400 200 100 400 200 204.2 keV Gate 258.8 210.9 keV Gate 511.! 248.4 keV Gate 668.1 258.8 keV Gate 204. 511.0 340.2 L 1000 Channel N umber Figure A. Channel Counts per 400 200 200 100 100 100 140 C.S. 511 keV 340.2 Gate 588.0 keV Gate 601.7 keV Gate 916.5 {P S 588.0 625.2 keV Gate 1000 Channel Figure A. (cont'd.). Number 141 0: 785.6 keV Gate 400 . L" (\l 200 > o a; \O i o ...; 0 _. 798.9 keV Gate 100 > H C m 00 ‘1- 810.4 keV Gate 100 t 442 3 668.1 Counts per Channel 0 5 836.3 keV Gate 200 ’ —-1 - a: ~o b \O 100 . 0 L 0 1000 Channel Number Figure A. (cont'd.). 142 100. 850.5 keV Gate H G) \O \O 0 —2 984.9 keV Gate '__ 200- ‘T U .—1 c b (I: G: :, ca 100» ' S '8 o I - ---1- ...... b ‘ L (p 0 . CL 0‘ v1 1059.3 keV Gate 1005 F: m a R '2 3 - N c: S :3 <3 0 0 e ox F: .3 1063.6 keV Gate 100L g 00 :2 «a U1 3 684.7 keV Gate 3 200 3 1 8: . :3 T fl 1 o N. g 0 100 3 h m- 1 a: LO co 0 . 694.0 keV Gate 200 ab ‘I ~ 5 . m 100 ' ' :1- ; i 0' I 0 g 1000 Channel Number - Figure C.‘ (cont'd.). 200 100 100 50 200 Counts per Channel 200 100 152 V 702.1 keV Gate 68%.? 728.3 keV Gate 402.6 882.0 777.6 keV Gate m m . 0 o m N m m m 1 196.6 1008.7 785.3 keV Gate From 777.6 keV gate 1000 Channel Number Figure C. (cont'd.). 100 400 200 Channel 200 100 Counts per 200 100 153 1 882.0 keV Gate :0 5 . N l\ q LO . L «5 911.4 keV Gate 0" q . 'l LO O ‘ b . :1: N O3 3 0 956.5 keV Gate b KO 1 15 0'1 . 1 995.7 keV Gate 9 £0 . (1‘1 . I go. ‘ l'\ N d D l\ 0 1000 Channel Number Figure C. (cont'd.). 154 APPENDIX D Angular Distribution Plots of 1“1Pm Transitions from (p12ny) Reaction. Figure D. Angular distribution plots of lule transitions ob- tained from (p,2nY) reaction. The data were taken in the 90-180° quadrant. INTENSITY INTENSITY 155 1.2 . 1.1 . 1.0 . .5 403.8 keV A2 3 "O .1010 .02 A. - 0.04:0.02 538.5 keV A2 = -o.34:o.02 A“ - 0.02:0.02 1.2 . 1.1 ..l 1.0 . .S. .8. 247.4 keV A2 = -o.25:0.12 Al+ = -o.o3:o.19 __‘7“‘:. A2 . 20.2810.22 438.8 keV I A“ = 0.25:0.25 ,51111111111"1111111 0'10 20°30‘10‘50'GO'70'80'300'10 ‘20“30‘10'50'60'70‘80'90' ANGLE Figure D. ANGLE INTENSITY INTENSITY 1.3 . 142. 1.1. 1.0 . 43. JB. 7' 156 A2 = 0.15:0.08 ‘- An = 0.19:0.11 531.3 keV 911.4 keV A2 = 0.04:0.02 An 8 0.12:0.02 123. 1.2. 1.11 1.0. .s- A2 = -0.08t0.02 A“: 324.6 keV 0.05:0.03 L l l l l l L 694.0 keV A2 a '0 . 11:0 .04 “ A“ a 0.09:0.06 .7’ 1 1. 0‘10 ‘zo‘ao‘w'so'eo'm‘ao'sob'm ANGLE Figure D. (cont'd.). 111111111 120130‘10150‘30170330130. ANGLE INTENSITY INTENSITY 157 1.5 . 837.1 keV 1.4 . 1.3 . 1.2 . 1.1. 1.0. A2 = 0.20:0.03 A“ = -0.06:0.04 .S 882.0 keV , A2 = 0.26:0.02 A4 = -0.11i0.04 1.5. 777.6 keV 1.‘+ . 2" a: A 1.2 . 1.1 . 1.0. A2 = 0.27:0.01 A: . -0. 05:0. 01 L4,1, l 1 A2 = 0.26:0.01 858.5 keV A1+ . -0. 02:0. 01 L, L,AL ANGLE Figure D. .S 0'10 '20‘30'40'50°607ol‘80|'3010'10 ‘20'30'HOSOIH'6070‘801'80' ANGLE (cont'd.). INTENSITY INTENSITY 158 1.1. 956.5 keV 130. 38. 33- 35- 3+. A2 = -0.30:0.07 An = -0.03:0.12 1153.3 keV A2 = -0.49:0.05 Al+ = -0.14:0.11 1-1- 785.3 keV 1.0 . 33. 33. .55. 3+. a. II -0.34t0.04 :1.» N ll 0.04:0.06 1008.7 keV .;//,.r—17-- A2 = -0.43:0.04 A1+ = ~0.lOt0.06 LL! [LILIIILLIIIIIL 0'10 aosofioso'eovo'ao'sobfiio ‘20‘30‘10‘50'60‘70'80'90' ANGLE Figure D. (cont'd.). ANGLE INTENSITY INTENSITY 159 1.9 . 1.8 . 1.7 . 1.6. 1.5. 1.11 . 1.3. 1.2. 1.1. 1.0. .9 . 1037.5 keV A2 = 0.35:0.09 A. . -0.03t0.16 1163.0 keV ‘ A2 . 0.29:0.03 } A. . -0.11:0.06 1.9 . 1.8 . 1.7 . 1.8 . 1.5 . 13+ . 1.3 . 1.2 .. 1.1 . 1.0 . 39- 995.7 keV 1045.9 keV A2 = 0.44:0.06 - 0.14:0.01 A. = 0.06:0.09 A. = -0.13:0.02 L111 LiLl 0'10 ‘20“30‘10‘50'60'70‘80'800'10 ‘20‘30‘10501'801'701'80'90' ANGLE Figure D. ANGLE (cont'd.). INTENSITY INTENSITY 160 1.1. 1.0 . 702.1 keV A2 = -0.90:0.03 A. . -0.15:0.06 1.1. 1.0. 3+. 684.7 keV A2 a -0.77iO .01 A“ = 0.06:0.02 I l L I ,0 1 1 1 1 0'10 20°30N030'6070'80'90' ANGLE Figure D. (cont'd.). Figure E. 161 APPENDIX E Gated Coincidence Spectra of Transitions in 141Pm from (a,4ny) Reaction. Integral coincidence and gated spectra of transitions in lule from (a,4ny) reaction. Background subtraction using the adjacent continuum has been included. The spectra are arranged according to increasing energy. 162 3.8.21 TNZT . .— . e, - e t . u .u a A“ \1 mm. A G G l a V .. V 1 V :.-m.l.. n e a. ... .... . - k W... 6 o.Nmmll 4 o www.1- . . 6 .m .m .L m .4 . a. 1. 1 9. Y 1.. 3 ..u 3 I. 1 1.“ m.mNhll.1 III“. 1‘ h.:®m\\\ : mm o.-m1 l .fo.-m c ~Hm\ 1 IHII . . .... ...? ..H ...-in II" Ass .0 .l 111-ll 11h w woull. m.~.m~ 1-1‘.m.0 1111.14.11” ..m ... . o o M. . m o .o 0 1 m m m s 1 .323: 0 3a 2530 1000 Number Channel Figure E. 163 h.-~_ m.c~c~ e e e e t t t t a mu mm a G o.-m . G a w. . ... w. w. k .K k l k 3 3 9 8 ,0 1. ,b 1. l4 8 2 3 no 1. A. .4 c mmm o.mmo 0 Han ~.m ~.mm: m.w~ m.~mm m.~mm ...m 4 . o.woN . m mm_ 9 wow o.wm~ 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 O 5 0 5 9. 1. .4 9. 1. .3 o. m2.5:... 0 3.. 25.50 1000 Channel Number (cont'd.). Figure E. 164 e e e e t t t t m .... m a o.mmo o.~mm V V V V e e e e k k k k .1” 8. nw 0” 9555 :5. M 02K w w 4. A. ,b ,0 0 0 0 l'1 miom m.am. ..m. D D D D D D D I o 0 0 0 0 0 0 0 0 0 0 O 0 .5 0 5 0 5 .occcco ton macsoo Number Channel (cont'd.). Figure E. 165 ‘1 684.7 keV Gate 200 » g ‘ 100 0 702.1 keV Gate 1, 100 1 ‘ 1: t: - 5 ‘ o . 8 50 1 g . t- 3 0 728.3 keV Gate ca 100 - m, C’. ‘ o- g g G: . “ 3; m 1 :1 2 o 50 .1. ‘ U 0 777.6 keV Gate 200 1 ‘ LO D 1‘0. 1 Ch 100 » 0 o A _ 1000 Channel Number Figure E. (cont'd.). 166 A.~.._ m m m.o~c. m m a a a a nu nu no .0 w w. w .. z. w. .K .K .x .K 3 0 8 7 o.~mm .L .h nw a“ 8 8 9 1 7 8 9 l l m.mme 5.... o.mmm . T V m.:o:||.1|11|| m .m: m .mm m..mm ..m.m ...... 8.8m. m em. 0 0 0 0 0 O 0 O 0 0 .U .5 no nu .5 n. .3 .l. 2 l 1.. 0 0 [4 once: 0 3a 2550 Number 1000 (cont'd.). T Channel Figure E. 167 APPENDIX F Angular Distribution Plots of 1“P111 Transitions from (a,4ny) Reaction. Figure F. Angular distribution plots of 1“P111 transitions ob- tained from (a,4nY) reaction. The data were taken in the 90-180° quadrant. INTENSITY INTENSITY 168 1.1. 1.0 . .3. .G. .5. 3+ 324.6 keV A2 -0.2610.07 A. = 0.02:0.09 426.9 keV {A2 8 -0.3910.04 A4 a 0.03:0.05 1.1 . 1.0 . .3. .5. 315.4 keV A2 a ‘0 .18i0 .05 A = 0.02:0.07 1. 1 l L 1. 346.3 keV A2 = -0.44:0.03 A. = -0.01:0.04 l .1 11_1 1 1 ,1} 1 1 1 1 1 0'10 I20"30‘+050"30'70“80'301)'10 ANGLE ‘ Figure F. 1 1 1 '20'30‘10'503070'80'30' ANGLE INTENSITY INTENSITY 169 1.1. 1.0 - .51. .E1. .7’. .iSJ .55- .'+ - 33- .2!- 653.9 keV A2 = -0.50:0.07 A. = 0.08:0.10 702.1 keV A2 . —0.59:0.02 A,+ = 0.01:0.03 1.1 - 1.0 - .51- .ii- .7'. .£3. .55- 3+- .21- 32.. 464.8 keV -0.22i0.05 A2 A. 0.12:0.07 LLilLL 684.7 keV A2 . -O.89t0.02 A. . 0.03:0.03 L l 1 010 20‘30‘10'50'30'70‘30'3011'10 ANGLE Figure F. (cont'd.). 1 L 1 l l 1 1 l I 20°30‘10‘50'60’70‘30'90' ANGLE INTENSITY INTENSITY 170 1.7. 1.8- 1.5- 13+ - 1.3 . 1.2 - 1.1- 1.0 - .3 7 A2 A. 28.3 keV = 0.28:0.03 a -0.02i0.05 837.1 keV I 0.22:0.08 A2 = A. . -0.06:O.12 1.7- 1.3 d 1.5 . 13+ . 1.3 - 1.2 - 1.1 . 1.0 - 455.1 keV A. I l. 0.30:0.06 fl 0.04:0.08 1D 777.6 keV A2 = 0.32:0.04 Ag = 0.01:0.06 ,9111111_1111111111 0'10 '2090'110'50’30'70'30'9011'10 '20‘30‘10'50'60‘70'80'90’ ANGLE Figure F. ANGLE (cont'd.). INTENSITY INTENSITY 171 1.9. 1.8. 1.7. 1.6. 1.5. 1.11.. 1.3. 1.2. 1.1. 1.0. 990.8 keV A2 = -o.-2:o.02 A“ = 0.02:0.03 1163.0 keV 1 A2 8 0.15:0.06 A“ = 0.02:0.09 882.0 keV TN A4 = -o.02:o.04 l 41 11_ l l l l l 1 995.7 keV I A2 = 0.41:0.03 A1+ = 0.03:0.04 , 1 1 1 1 1 1 1 1 1 0°10 “20°30‘1050'ea'70‘ao'so'o'10 “211"a0'11o"511“so’7o'30"911o ANGLE Figure F. (cont'd.). ANGLE INTENSITY INTENSITY 172 1'11 785.3 keV 1.0. .8. .8. .7. .G- .5. .‘L .3. .2 ‘ 1.1 .1 A2 = -o.93:o.09 A4 = 0.27:0.12 140.6 keV 1.0 u .‘+. A2 = -o.13:o.07 A = -0.03:0.10 03-1 1+ ,2 1 L 1 1 1 1 1 1 1 0°10 20°30‘10‘50'GO'70‘80'30' ' ANGLE Figure F. (cont'd.). Figure G. 173 APPENDIX G Gated Coincidence Spectra of Transitions in 139Pr from (p,2ny) Reaction. Integral coincidence and gated spectra of transitions in 139Pr from (p,2ny) reaction. Background subtraction using the adjacent continuum has been included. The spectra are arranged according to increasing energy. 174 I r r I r I 1 I m i H J m .l U 1 .—1 m ._ 3» M Q) 1 on .x 1 d) U 0‘ a o 01-4 0’"! | H w .4 Z'SOII-————’ ' I 9‘6801 Z§SE§$_Z::: L'hIOI E 286 ‘3 c: I Jr. 1' I ‘ g 3°006’ 9°806” r f 8‘LZ 9‘80 I.9€‘ as; ['994 h L . .QOL .[0L [‘80L ['fOZ— 5'009 fi‘6QS‘—'——" L'LhS 0°?IEI 7‘ 8'9Lh" .. S'Séfi . Z'SOh . €____ 9 399“: 8°hsz‘ 0 ~ . 9 9h 0 9h?! h 6 z h°6IZ I 661/ 6'SII L 1 L 1 L l c tn 1' m <3 <3 <3 <3 <3 <3 ...1 H H O O lauuoqo 13d swnog 'Numbor Channel Figure G. 175 m N.oom .9... a m N com a a a a nu nu nu nu w. w. w w. .K .K .K .K 7. 1. 1. .4 H mm my. 125'. m . ...: 1. 11 1. ~.~om\\\ .4 3&3 3.2m 3.:m Ncma: omou omoo weomm o.w:N . ...mHN : 54:; ummm. m.m- no nu no 2 l 3 5 0 O 0 0 1. 7. 1. .4 7. .O:€O£U .oe 3:330 1000 Channel Number (cont'd.). Figure G. 176 d e e e e t t t t a a a a .u .u nu nu V_ v. V. v. e e e e .K .K .K .K n. .o 9. .3 ,o ,o R. .3 I4 3 0 7 2 3 4 l4 o.N~m :.m.~ :.m.~ . m :m. m.m- 0 0 0 0 0 0 m 0 0 0 0 S 4 2 1 3 l 2 .eccogo .2. 3.2.00. 1000 Channel Namber (cont'd.). Figure G. Counts per Channel 100 50 1'00 50 100 50 100 50 177 —-—-"ll3.9 l13.9 113.9 0'1 o on F. F4 Q) 0 LO 3' 0 1n N N O M ——-—-'219.l1 1000 547.7 keV Gate 708.1 622.3 keV Gate 809.5 .———910.1 698.3 keV Gate 701.1 keV Gate F" 0 CD 0 [\ Channel Number Figure G. (cont'd.). 178 N.mo-l m . m .... m a N com a a a G G G G V V V V m 9831.1 ...... b... .m l 1.. 2 l 8 e o 0 . 2:. we. m . woe m 7 7 9 9 5.3? . 0 0 0 1 3.0mmlll 3.0mm 0.:mN/ . o.@:ml|.||| o o:N : «LN . ...mHN NHmhfi. m.mH~ m.m: m.m: D D I D b L P b F D b D o 0 0 0 0 0 0 0 0 O 0 0 0 5 0 0 6 3 5 2 3 2 0 5 l o .oecoco .oa mac: 0 Number Channel (cont'd.). Figure G. 179 APPENDIX H Angular Distribution Plots of 139Pr Transitions from (p,2ny) Reaction. Figure H. Angular distribution plots of 139Pr transitions ob- tained from (p,2ny) reaction. The data were taken in the 90-l80° quadrant. INTENSITY INTENSITY 180 1.2 . 219 .4 1.1. 1.0 . £3- keV A2 = -o.25:o.03 A. = 0.03:0.03 405.2 keV A2 = -o.11:o.02 Al+ . 0.03:0.03 1J2. 184.3 keV 254.8 keV 1014 1.0. I T T I .9. .8. 7 A2 . -o.14:o.os A2 = —0.08i-l).02 A“ a -0.06:0.08 A. a -0.05:0.02 l l l l L L. l L 1, I l 1 l L l l J l 0'10 20°30‘10'50'eo'70‘eo'sob‘10 ‘20“30‘10‘50'60'70‘30‘90' ANGLE ANGLE Figure H. INTENSITY INTENSITY 181 1-2- 246.0 keV 547.7 keV 1.1-I 1.0-1 .94 .8. .7. .6. A2 = -O.381:0.08 A2 = -o.35:o.01 A.+ - -o.03:o.12 A“ - 0.07:0.03 OS. 1-2- 199.1 keV 336.6 keV 1.1. 1.0- I .9- 08-1 .7. 1 A2 = -o.32:o.11 A2 = -o.35:o.03 06-1 A“ . -o.09:o.12 A” = -o.os:o.04 I 1 1 1 1 l 1 I l ,5 1 1 L 1 1 1 1 1 1 0‘10 ‘20“30‘10‘50'60’70‘30'9011'10 ‘20“30‘1050'6070‘80'30' ANGLE ANGLE Figure H. (cont'd.). INTENSITY INTENSITY 182 1.'-l' . 1.3 . 1.2 . 1.1. 1.0 . .8 809.5 keV A2 = 0.13:0.04 A“ 3 0.09i0.06 900.2 keV A2 = 0.20:0.01 A. - -0.08:0.01 1.‘+ . 1.3 . 1.2 . 1.1 . 1.0 . 738.1 keV A2 = O.l8i0.02 -0.04i0.03 Au 827.8 keV 0.11:0.02 {p N u - -0.0li0.03 } ;> J? l l l 1 l 1. l Figure H. ,3111111111111 0‘10 “20°30‘10'5g‘lseo’70‘ao‘sob‘m ‘20‘30‘10‘50'60'70 o'ao' AN L ANGLE (cont'd.). 183 1.1. 910.1 keV 1075.2 keV 1.0 . AS. INTENSITY A2 . -o.21:o.01 A2 = -o.15:o.os A. - 0.10:0.01 Al+ . -o.os:o.o7 1'11 802.5 keV <- - 917.1 keV 1.0 . AS. '8‘ .1 " \. -”////A A -0.20:0.07 INTENSITY 2 a -o.19:o.04 ' -0.02i0.13 3> .1:- I A a 0.15:0.06 ,7 1 1 1 1 1 1 1 1 1 1 1 1 g 1 1 1 1 1 0'10 '20“ao‘+o‘so°eo'70°eo'sob‘lo '20‘3011050'60'70‘80'90' ANGLE ‘ANGLE Figure H. (cont'd.). INTENSITY INTENSITY 184 1.1. 1.0- 39. 33. 3’. .53. 35. 3+. 33. 32. 1014.7 keV A2 = -0.38:0.04 A“ . 0.07:0.04 1369.7 keV 3 A2 = -O.68:0.07 Au . 0.09:0.10 1.1. 1.0 . .51. .53. 37. 33. 35. 3+. 33. 32. 701.1 keV A2 = -0.87:O.13 Au . 0.10:0.20 1105.2 keV A2 = -o.59:o.1o A.+ = 0.18:0.12 ANGLE Figure H. (cont'd.). 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0'10 209090503070'30'9013'10 '20'30‘10'50'60'70'80'30' ANGLE Figure I-l. 185 APPENDIX I Gated Coincidence Spectra of Transitions in 139Pr from (a,4ny) Reaction. Y-integral coincidence and Y-gated spectra (identifying high energy coincidences) of transi- tions in 139Pr from (a,4ny) reaction. Background subtraction using the adjacent continuum has been included. The spectra are arranged according to increasing energy. 186 " V r ' L'OEEI L'OEEI . 1 3 Q - m 3 go .5 '5 >1 :5 ‘ .3 a 3 . 3 U . ‘. I: . 61. 0'1 '7 L hIOI c, _4 7i VD H- . >" 1 S .OI6\ . 2'006 ~ 2 005 Z'OOG 0°zze 4‘618“‘ 2'619. 2'992 I 88‘ I'BEL 1'902 . I 104" I'QOL I‘IOL/ 9°889 6°909 Z‘BSS— E’Ehg’ Fees 3 0°IIS ‘ “-2 I'hSh 323g 3‘ S'hhh-—- h e'zo 0'08? . 0°9fi2\ . S'th , 9 ”"3 . h°61 h etz . - -—o hIZ €°0 Z s 002 ~- “I'661 L'SLI 6’EII L A ‘ <3 <3 é? E? (3:: L0 :1- m 0 In O U“ 53 53 53 5% a. 2 >< x > > > a £2 3 x O h m 0 O I c 3 3 3 c H H H to u 3m 6'909"' E'Eh ° c: S f EHS ‘3 0 [[9 C) P I'hSh 9'988 .800 0'0 0'9hZ E‘OOZ L°6Lt ‘ ‘ L ‘ * 7C3 8 a o 8 ° 8 8 ° (*3 PH m Q N [GUUDUQIJS Q. 250' swnoo Number Channel (cont'd.). Figure I-1. 188 f fi 1 3 L'OEEI I 1 U) ; m . u . 3 3 >2 f m w w' H U > m a: Q) 00 00 M I l X X ,\ an >- >» . a) Q) 0 .3 x. O N G. <1: + \1 Ch b b H H H N N O" 0" H \“Z'OOG 3'00 L'618 L°618 L°98L [.IOZ 80L\ 6‘909 z‘ess . EOE”? E 9'79 o'tts P ‘F 0'9 8‘292 I. o 9‘9EE 0°922' 9 988 O o O o 082. : o 08 0'9 . S 0‘9fiZ - ° / 2.3;“ 21355 °..'nr . L'GLI s 291 G'EII O O O O O C In C O m N N H lauuoqg 13d s;un03 2000 1000 Channel Number (cont'd.). Figure I-l. 189 lauuoug Jed slunag Q 3 55 2.: 3° 2° e° >'< >< >4 > > > G) 3 3 x D m o. o. 3 o o \D g 2'006 g N z‘oos L'6I8 L°98L ['80L I'QOL E'EHS O'IIS 0°98 9.9EE// 0 gas 6°862 . ~ 0°9nz h GLZA h'SIZ E'OOZ . L'SLI L 6L1 6°€II <3 <3 <3 3: L E?’ c: <3 <3 0 3 c3 8 2 8 .3 2000 Number (cont'd.). 1000 Channel Figure I-l. 190 L’OSEI O b 3 3 g) m m . ? ? >< >< >< > > > O (D .2 .2 And, ‘2 ‘9 ‘3 <9 <0 .6 N m 2 g z‘ooe 2'006 4 z'oos L°98L L'98L [‘88 g I'SOL I'BOL , 4 t‘to 4 l j 6'909 l E'shs E‘Eng 1 O'IIS « f 0°9sn 9 hhh 9'hfi // 1 . 0'98h 8 20h j 9 988 .9 0'92: 3 9 929 ‘1 0'9hZ ; 0'9nz . - “ *1 an . +1.6“ ‘ +7911 9 m: j +. an . O .002 s 002 . 8.002 - rest/é £54k .4- . L’GLI/ A S 3 j 5'3 O'BZI- ‘ A J_ A L gjr_ - - f . - U U C O O O O C q 8 8 53 8 [auuaug Jed slunao- 2000 -1000 Number (cont'd.). Channel Figure I-1. 191 V ' r ' V ' V— r r r L'OEEI-—- - L'OEEI a) a: d.) U u «U to to CU 9° 9° :0 >< >< >4 % % 3 .2 .24 .34 co co 0 IQ» N ln n O N m 4 x >- >. =- D G) a) 0 .2 .2 .x O. \O \O \O . \T h m 0 ‘7 z 006 :7, z 006 g L'98L- 4°99£ I'90L.__ . I'IOL"' I 80‘ e.gfigs 8.8179 p 9‘000 9'988 9'922 L°6LI A ELI o'ezr.3“ 6‘EIP- — 6'8II-— O O O O O O O O O O O O 0 mm x? N N .—l .—o lauuaqo Jed srunog (H30 1000 Number (cont'd.). Channel Figure I-l. 193 Q) Q 0 U U U Q <0 N 9° 9° 9° >4 >< >< ‘3 E ‘3 .3 x x ("1 N 0‘ ' 2'006 ' - __. ’ 5; :g z 006 3: U" W In L'6t9-4- 1'904._. t'80£--- t°904 6'909-— z 999 E'Ehg. 92hhfi-__. 0 9Eh——- S‘8Ih-—- 9'966 ‘ 9'988 9'9€€-—- 0'929” 0‘082-—- S'th ~ 0'9hZ 0°9hZ h'SIZ 8,00 : h°SIZE.OOZ . ,3 _ _ L°6LI L 655-—“ 9 ZBI . 6'EII 6'6II 6‘str—- <3 c: <3 <3 <3 <3 <3 <3 G O O O O m \‘f N N H H |auuou 3 mad slunag 2000 1000 Number (cont'd.). Channel 194 GJ Cl Ql U u H cu to CU 9° 9° 9° x >< x >9 >. :> Q) a: 0 .z .2 .2 0‘ In ‘0 In an m O H (*3 <0 ‘0 . ‘9 . 3.006 Z 006 Z 006 1’804 I'80L 0°90€-—— 9'962"' O'Shz O'9hZ h'GI h‘etz h‘6tz 2'002 , L 6L1 a, L a ‘ o :3 ‘ 2: ‘ o In C U“ H H |auuou 3 '0 19d 2000 1000 Number Channel (cont'd.). Figure I-l. 19S L’OSEI-- 9° 9° °"° ° x x >5: L'fiIOI g 9 9, 9. N M .3 .2 H H H E; 53 z'ooe g; N I'\ N L'6I8-" I 80‘ I'IOL"' €°EhS"’ 23 c: . '- 0°9en-—— S'BIh‘"’ ; S'BIh"‘ - e'zon , __ 9‘gg€_ 9.988s a 0'9hZ [.369‘3 63;: h'GIZ L'6Lt" ' L'GLI 6'EII G'EII B‘hL-' A L A L l P L L A A L .° C O 0 <3 <3 53 53 5° 53 53 N H Q N N H Iauuoug 18d slunoo Number (cont'd.). Channel Figure I-l. 196 1000 0 (D a) U U H CO <0 <0 9° 9° 9° >< >4 >< > > > m G.) 0 x x x [N N N \O O\ C an H O Ix co 6‘ 2'006 - 2'006 L°6I8 4'618 I'804 - I'eo; I‘BOL I'IOL/ €°EhS 9.+?+HT\ 0'960”' QWmh 9'988 i 0'992 - ° h'6IZ g h 652 e‘oozr L'SLI ‘ 6‘6II O O O O O O O In C O <-< N ...4 | a uub llO 2000 Number Channel (cont'd.). Figure I-l. Figure I-2.. 197 X-integral coincidence and X-gated spectra (identifying low energy coincidences) of transi- tions in 139Pr from (a,4n7) reaction. Background subtraction using the adjacent continuum has been included. The spectra are arranged according to increasing energy. 198 r 5 5 m L'hIOI 3 CU l“ >« > 0 o a) x 2.006 a 3.006 g; 2.006 ,2 9 : 9L2 > N 3 {619 h i . E. L‘99L/ 5. a; 3 4°99L—-—-— >l€ N H ‘ 'reeL H g ‘“ ° [.80L\ I. I904 . 9?étoz// 9 IOL“' 9'889-—- _ s°9I- . 6°909- 6 909-—- 6°ZGS’ 2°999- 2'995._. ° —-—-—— 2.8SS ‘ — s Eth’LZS-—' 6 £05 . 0“n9 " ' I'hSh—~ 095332, 0°99: 9919 920+— 920 9'239222“‘ 9‘296 g‘zgg___ 9.988 '99 :7' 9°"58 O'Sfi€-——- 3", '51) «a 9968 0 928 o'gzg—" 1 - 6‘862-— : . 0' 92- ; 0 092 Fo‘ehg.092_—- 5' 5 o’ _ , * 999—. 1 h 6509 0 9h? g-fihzz/’ ;] h'GIZ S’fihZ i .111 ’ g / V. 0.11 f . 3.91999 " * 1W7???- L GLI L'GLI/ o;9zr-—- O'BZI .~ 55“ smtt ewtt 919*' zm9 a 3591- ‘“" LO :1- m L A A l A 4 A O O O O O O O O 0 <4 .3 F4 <3 tn <3 ‘0 0‘ \‘I‘ 0‘ \T | a uu ou’o' «.l'ad sguna 3 4000 2000 Number Channel Figure I-2. 199 |auuoq3 1800810003 :3 r r f r T V V r fir f ' ' O c . v a. a, m , t; z‘ooe t; 3'006 ‘5 Z 006"— e° a” a“ >~ >< >a % . 3 3 ‘72 L'99L 0. L'98L—" <12 13994—— ’ as \o ~o H ‘1’ N N N M 0 .0 9'889- E 6‘909— Q 3 : OZ r999” 3 . . -‘ 0 1 c: . ' I'hSh" - __ : 0°929’ ; 9 ""‘W‘sen .' 0‘99: 0 8'20h 3 8'ZOh’ I S'ZOh g 8,” . . 0 0°§§us—— 6} '19 ’ 3 9°9€€ . 9 988'- 1 0'9z9’ o 932—“ 9 6.552— 6°86 _... 0’092— o-oezi— ‘ O . h swuz/ , +1 61L 9 h z . E'OOZ 0 fiIZ~ g° 0 . I/ h an I‘GGT’ g'zat\ 1'66? 9'29I\ . L'GLI L'GLI ‘ 6‘1 0'92I—- ‘ , ' at 6.8” 6.8” e 81? 2'09 . . 0 9+.— A L n L L A A L _L_ L _L k c O Q g 8 ° 8 8 ° 8 m 0‘ ‘1. Ch q M H (cont'd.) 0 Figure 1-2. 200 O '_‘I v r v i r *7— T’ I r o ‘0 db III-V ' I 1 4 4 1 2.0061 2'006 0064 0 Q) G) u i u u «I (U 1 ‘0 Q 4 60 50 00 I ; I I >~ 1 >* >" 1 > > > .32 L‘98L——“_ 3 3 \O N \D 8 3 3 {.804 O O o. N. 0'9Efi 0'9ZE fi'SIZ ”96:92 a {5689;4' , ' I. 6LI . 6°€II 6 EII L L A_ 4 A A n o O O O O O O O in O as m H <2- Iauuoqg 18d sIuno Number (cont'd.). Channel 201 O v 1 r r I v t f .— fi' f v v o O p 1- {I in? 1 I J 1 i 1 I 1 z‘oos-I' z'ooe -I m I m m u I u U 1 m m m 3’" ‘i° ‘3” ' >4 >1 >" 1 9 9 9 P x L 98L— .x =4 L'98L—1 so FI «a J 9' r? ‘ 9 3 9 . i ‘ h- 0 .0 6.909‘ E A 3 v6 92 9 E'SfiS O~ O Q O F N:— V v 0 c “I' c H O 3 .C E U g. 9.988 , h'GIZ +7613 E'OO 5'211 6’8II 2'09 L ‘ L ‘ 0 <3 <3 <3 <3 c> <3 G O C C q- N »O M Iénnnqoliad sIunog 202 1 recs—- 3 3‘005“. 3 3 In 1 cu m ?° I “I" I” >-: >< >1 > , j :> > ID 0 3 L (519-4 x .3. ~ 3L o~ 9 9 g 9 9 In 1 O \O O'9fiZ h'etz' h'SIZ s‘ooz s'ooz 9'2It 6'EII 9 9 9 9 9 m H H IauIqu 3 "Iad swnog O O O Q h- o .9 E5 ,; 39’ :23 68 O o N--V o c: a: :34 °e 4:: a .2? Um 203 3 V V 1 r ‘r V r f T r T7 r O J G: - Q Q 1 o 3 u woos-1 ... 2'009 m m m 2° 9° I 9° w w I w % 3 rate-‘ 1:, L‘6I8 .Y- x I x H H in I‘. .4 co 1 \O O O m N IN I N [.8“, 1; I'SOL 1 h I I, .13 6’909— E :3 . - oz 9 ens— e 2419. o o N 1’ 9'hfih... C 0'999/ o'ggfi/ : S'Bth 9 ZOh/ O .1: 9'988— 9-925— 9'9E£-—— o 0922/ 0922/ . 0’9fiZ 0‘9hZ o 992 g'fifiz 9°hhz——"' n'etz h BIZ $.002 n'stz I'set I'66I\ 9'ooz L'BLI’ L'GLI’ 6'EII/ . 6’EII 6 EII 0'9h-—-- A I A A L A A L A 7 c O O O O O O O O o In In 0 O N "4 x? N r-I Iauuoq 3 19d saunog (cont'd.)9 Figure I—2. 204 819.7 keV Y-gate h°6IZ 4000 - ‘4 AhA 3'0064 A—A M‘ J “A I°8€L 900.2 keV Y-gate 1014.7 keV Y-gate I°80L 2000 Number (cont'd.). Channel Figure 1—2. G'SII 500 l 900 . 400 I IaUUaaj‘Jad Slunog 205 2'006\ 2°006—- Cl 0.) U U CO CO 9° 9° w w > > Q) Q) .3. .2 ‘7. I'804--" ". m 0 N m H M H H S'EhS’ 9Wns- 0°9zs— 0'992 0'9hZ h'GIZ h'6IZ EWm2-—', 9.28I" — e 6'EII 6'SII <3 <3 G: <3 <3 <3 0 In C O 3 H 7 .. V N . - H -. auuaqa Jad s;un03 4000 2000 Number Channel (cont'd.). Figure I—2. 206 APPENDIX J Angular Distribution Plots of 139Pr Transitions from (a,4ny) Reaction. Figure J. Angular distribution plots of 139Pr transitions ob- tained from (a,4ny) reaction. The data were taken in the 90-180° quadrant. INTENSITY INTENSITY 207 1.2 . 1.1 . .... I C: I in l ‘u I .EB. 45 128.0 keV A2 = -o.29:o.09 Al+ . 0.09:0.14 199.1 keV A2 . -O.28:0.06 3| A“ . 0015:0007 1.2 .. 1.1 . 1.0. 60.2 keV A2 = -o.03:o.o9 A“ = -o.os:o.14 179.7 keV A2 = -o.34:o.03 A“ = 0.02:0.04 1 3L, L l l L, L ANGLE Figure J. ,SllllLilLLll 0'10 “20309030“50’7090’909‘10 ‘20‘90‘90‘50‘90‘70‘9090" ANGLE INTENSITY INTENSITY 208 142. 1.1. 1.0 . in I .E!. .7’. .s. .55. 3+ 219.4 keV -O.28i0.03 > to II 0.03:0.04 {p .:.- ll 280.0 keV A“ . 0.04:0.03 1.2 . 1.1 . 1A0. .53. .53. .7’. .ES. .5. 200.3 keV " A2 . -0.26i0.12 A“ = -o.19:o.14 246.0 keV A2 a -o.44:o.04 An = 0.03:0.04 L l l ANGLE Figure J. (cont'd.). ,HIIILIIIIIILJIILI 0'10 ‘zo’aolIo‘so'so'zo‘ao'somo “20‘so*+o“so°sovo°so‘so° ANGLE INTENSITY INTENSITY 209 1'2“ 326.0 keV 1.1 . 1.0 . .54 A2 . -o.31:o.03 A“ - -o.01:o.04 345.1 keV A2 = -o.49:o.07 A“ - 0.07:0.09 293.9 keV 1.1. 1.0 - :3. A2 . -o.3s:o.07 ISq A1+ = -o.03:o.o7 336.6 keV A2 = -o.41:o.03 A1+ = 0.01:0.04 ANGLE Figure J. ,l-lIIIIIIIIILIIIIIIII 0'10 ‘20“3090‘50‘90‘70'90'90‘b'10 ‘20“30‘40'50'60’70‘80'90’ (cont'd.). ANGLE INTENSITY INTENSITY 210 1.5. 444 .6 keV 1.4 . 1.2 . 1.1 1'04 A2= 0.23.90.03 618.5 keV A2 = 0.23:0.09 A“ a O oOSiO .12 1-5J -- T 402.9 keV 1.9. \ 1.3. l' 1.2. 1.1 . 10 A2= 0.29:0.07 A = -0.0830.08 454.1 keV A2 = 0.20:0.02 An = 0.01:0.03 I ' 1 l l l ANGLE Figure J. ,SllllLllLllll. 0'10 20%09050‘90‘70‘90‘300‘10 'zo‘ao'lw'so‘so’m'so 0° (cont'd.). ANGLE INTENSITY INTENSITY 211 1.1 . 1.0 cl JI 543.3 keV A2 = -O.34t0.03 An 8 0.04:0.04 919.7 keV I A2 a -O.26i0.06 A” = 0.01:0.07 1.1 . 1.0 . £3- 436.0 keV A2 = -0.46t0.03 A“ = 0.04:0.04 786.7 keV A2 = -0.26:0.05 An = -0.10i0.05 ANGLE Figure J. (cont'd.). I I I In I I I. 0 ,HIIIIIILILLI 0'10 20°30‘90‘5090‘70'90'so'0'10 203090509070 0'90 ANGLE INTENSITY INTENSITY 212 1.1 . 1.0 . .53. .53. .7’. .53. .9. .3. .2. .1. .0 605.9 keV i A2 a -0.69:0.09 A. = 0.05:0.13 1.1 . 1.0 . .53. .53- .7'. .ES. .55. JI. £3- .22. .1. 558.2 keV A2 = -0.6li0.04 A.“ = 0.06:0.05 701.1 keV A. = 0.11:0.10 ,0 I I_I I I J I I I 0'10 ‘20‘30‘I0‘50‘9070‘90'90 ANGLE Figure J. (cont'd.). I I I I I I I L 0‘3090'50'90'70'90'30' ANGLE INTENSITY INTENSITY 213 1.'-I I 1.3 . 1.2. 1.1. 1.0. .8 900.2 keV A2 = 0.23:0.03 Au 8 -0.07t0.04 1.4 . 1.3. 1.2 . 1.1 . 1.0 . 738.1 keV A2 a 0.15:0.04 A. . -0.02:0.05 1330.7 keV A2 3 0.19:0.03 A. = -0.03:0.04 ANGLE Figure J. (cont'd.). .SIIIIIIJIIIIIILIILL 0'10 20%090'5030'70'90‘900’10 20'30‘90'50‘60'70‘90'90' ANGLE ST "'11111111131111!fllflflfllfllfllfllfllflll'Es