E-NEUXSTIC PROTON SCATTERING FROM 333 BA AND .144 SM AND rrs MICROSCOPIC INTERPRETATION f, ,, .3." 195,1; fh‘esi-s for the Degree of Ph. D; f woman STATE UNIVERSE?! DUANE CLARK LARSON 122212 . ,3 3‘ LIBR A R Y ' Michigan State University This is to certify that the thesis entitled . . m l . . presented by has been accepted towards fulfillment of the requirements for P‘LQD degreein P J‘I’CS W Major professor Damm— 0-7639 PLACE IN RETURN BOX to remove this checkout from your record. To AVOID FINES return on or before date due. MAY BE RECALLED with earlier due date if requested. DATE DUE DATE DUE DATE DUE 6/01 c:/CIRC/DateDue.p65-p. 15 ABSTRACT INELASTIC PROTON SCATTERING FROM 138BA and 1445M AND ITs MICROSCOPIC INTERPRETATION BY Duane Clark Larson Differential cross sections for elastic and inelastic 138 1“Sm have been scattering of 30 MeV protons by Ba and measured. The total resolution for the inelastic peaks was 7-10 keV FWHM, which permitted the observation of 20 excited 133 144Sm below Ex=3.4 nev. and states in Ba and 18 states in measurement of excitation energies accurate to 2 keV or less for these states. Based on characteristic shapes derived from angular distributions to states of known J", spin-parity assignments are made for the majority of the observed states. Collective model DWBA calculations were performed and deform- ation parameters extracted for all states of assigned J". Microscopic DWBA calculations which included the exchange amplitude were performed for the 2;,2' 41,2 and 61,2 states in both nuclei, using large-basis shell model wave functions to describe the nuclear states. These wave functions also provide an excellent description of the excited states in 138 144 Ba, and a good description of the energy levels in Sm, as measured in our experiments. The two-body force used in Duane Clark Larson The inelastic scattering calculations was obtained from a recent survey of inelastic scattering analyses. Polarization charges for the nucleons were extracted, and found to be essentially state and multipOle independent. Two sets of shell model wave functions were employed for the 1383a calculation, and it was found that inelastic proton scatter— ing clearly distinguished between the two sets, thus providing a sensitive test of the wave functions. Careful consid- eration of the transition densities derived from the wave functions enable one to directly study the pr0perties of the wave functions. INELASTIC PROTON SCATTERING FROM 1383A AND 1448M AND ITS MICROSCOPIC INTERPRETATION BY Duane Clark Larson A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Physics 1972 ®\ ACKNOWLEDGEMENTS I would like to thank the entire Cyclotron staff for their many kindnesses which made these experiments possible. Specific thanks are due the following peOple: Dr. Stan Fox for his cool head during difficult experimental times; Drs. Helmut Laumer and Lola Panaggabean for standby help during data taking; Richard Au for immeasurable computer assistance; Norval Mercer and the machine shop staff for various favors; Andy Kaye for procuring materials and photo- graphs with utmost efficiency; Professor Hugh McManus, Dr. Fred Petrovich and the rest of the theoretical group for many valuable discussions; Julie Perkins for typing this thesis; Dr. Barry Preedom for taking time to relate the story of DWBA theory, and many useful discussions; My thesis advisor, Professor Sam Austin for his help in all aspects of this work, especially during the data taking and the writing of this paper; Professor Hobson Wildenthal, whose influences are present in all aspects of this work, for introducing me to many facets of nuclear physics, especially the shell model, and for providing a home for my tractor; ii My wife, Dr. Nancy Larson, for help in data taking, and frequent discussions of theoretical problems associated with this work, as well as cooking my meals; My parents, for their continuous encouragement of my educational pursuits; and finally, I acknowledge the financial support of the NSF, and a three year NASA Traineeship during my graduate studies. iii TABLE OF CONTENTS Page ACKNOWLEDGEMENTS . . . . . '. . . . . . . . ii LIST OF TABLES O O O O O O O O O O O O O 0 Vi LIST OF FIGURES . . . . . . . . . . . . . vii I 0 INTRODUCTION 0 O O I O O I O O O O 1 II 0 EDERIMENTAL O 0 O O O O O O O O O 6 A. Proton Beam and Particle Detection. . . 6 B. Preparation of Targets. . . . . . . 8 C. High Resolution System. . . . . . . 9 III. EXPERIMENTAL RESULTS. . . . . . . . . 11 A. Energies of States in 1383a and 144Sm. 11 B. Angular Distributions . . . . . . . 12 C. Discussion of States in 138Ba . . . . 14 1. 2+ States. . . . . . . . . . 15 ‘ 2 O 3- States 0 O O O O O O O O O 16 3 0 4+ States 0 O O I O O O O O O 16 4. 6+ States. . . . . . . . . . l9 5. Other States. . . . . . . . . 20 D. Discussion of States in 144Sm . . . . 21 l C 2+ States 0 O O I O I O O O O 21 2. 3’ States. . . . . . . . . . 22 3. 4* States. . . . . . . . . . 22 4 C 6+ States 0 I O O O . O O O O O 23 5. Other States. . . . . . . . . 24 IV. =82 WAVE FUNCTIONS . . . . . . . . . 26 A. Conventional Shell-Model . . . . . . 26 B. Other Structure Calculations. . . . . 29 V. OPTICAL MODEL . . . . . . . . . . . 31 iv VI. VII. VIII. ’ DWBA THEORY. . . . . . . . . . . A. ~Collective Model. . . . . . B. MicroscOpic Model . . . . . . Distorted Wave Calculations. . Spectrosc0pic Amplitudes. . . Elements of the DWBA Formalism (Direct Amplitudes). . . . . Transition Density. . . . . . Discussion of Selection Rules and Non-Normal Parity States . . . Ul-b NNH I O O O O O O 0 DISCUSSION OF RESULTS . . . . . . . A. Comparison of Shell Model Calculations to Experiment . . . . . . . B. Collective Model Results . . . . . C. Microscopic Model Analysis . . . . 1. MicroscOpic DWBA Calculations for 138Ba 0 O O O O I O O O 2. Calculations with Other Forces. . 3. Microscopic DWBA Calculations for 1448!“ O O O O I I O O I CONCLU S I ON 0 O O O O O I O O O 0 REFERENCES 0 O O O O O O O O O O O O 0 APPENDIX A. B. C. TABES O O O O O O O O O O O O FIGURES O O O O O O O O O O O O COMPILATION OF EXPERIMENTAL ANGULAR DISTRIBUTIONS . . . . . . . . . Page 34 34 36 36 37 38 42 46 50 50 52 54 56 62 64 67 70 74 81 105 LIST OF TABLES Table Page 1. Energy Levels of 1383a and 144Sm. . . . . 75 2. Optical Model Parameters for 138Ba(1448m). . 76 3. Deformation Lengths and Transition Strengths for 1338a and 144Sm . . . . . . . . 77 4. Polarization Charges for Transitions in . Ba I I I I I I I I I I I I I 78 5. Major Components of 0+ and 62 Wave Functions Calculated with BotE Interactions, and the Resulting Transition Densities. . . . . 79 6. Comparison of Direct and Direct + Exchange Cross Sections for Various Interactions in 1383a I I I I I I I I I I I I 80 vi Figure 1. LIST OF FIGURES Page Slit and counter arrangement of high resolution measurement-Optimization- stabilization system located in the focal plane of the spectrograph. The experimental parameters are adjusted until the maximum amount of elastically scattered beam passes between the brass jaws, thus insuring minimum line widths of the groups of scattered particles along the focal plane. . 82 Spectrum of 138Ba(p,p') at 35 degrees, with resolution of about 10 keV, FWHM. The broad bumps correspond to protons which scatter from Mg and Si impurities and because of kinematic differences‘have planes of focus in the spectrograph. The yields of the 2+ state at 1436 keV and of the 3' state at 2881 keV were too intense to be counted on this plate I I I I I I I I I I I I 83 Spectrum from 144Sm(p,p') at 40 degrees, with resolution of about 7 keV, FWHM. The broad bumps under certain of the peaks correspond to protons which scatter from Mg and Si impurities, as in the 138Ba spectrum. The yield of the 3' state at 1811 keV was too intense to be counted on this plate . . 84 Elastic scattering.angular distributions measured for 1388a and 144Sm. The curves are results of Optical model calculations made with the Optical model parameters of Becchetti and Greenlees (Ref. 34) . . . . 85 Characteristic curves obtained by averaging our measured angular distributions from groups of states in 1383a and 1 48m which . had previously assigned J1T values . . . . 86 vii Figure 6. 10. 11. 12. States in 138Ba which have angular distri- butions in agreement with the characteristic 2+ shape, which is the line drawn, through the data. we assign all of these states J"=2+ with the exception of the state at 3050 keV. . . . . . . . . . . . . States in 144Sm which have angular distri- butions in agreement with the characteristic 2+ shape, which is the line drawn through the data. We assign all of these states J"=2+ States in 138Ba and 144Sm which have angular distributions in agreement with the charact- eristic 3' shape, which is the line drawn through the data. We assign these states Jfl=3.- I I I I I I I I I I I I I I States in 138Ba which have angular distri- butions in agreement with the characteristic 4+ shape, which is the line drawn through the data. We assign all of these states J‘"=4+ . States in 144Sm which have angular distri— butions in agreement with the characteristic 4+ shape, which is the line drawn through the data. We assign all of these states J"=4 I I I I I I I I I I I I I I Angular distributions for the previously assigned 6+ state at 2090 keV, and the weak 2201 keV member of a doublet. Both the 4+ and 6+ characteristic curves are drawn through this anguli£4distribution. The 2324 keV state in Sm has been assigned 6+, but due to the rise of the data at for- ward angles, this state may be a close lying doublet. We assign J =6+ to the 3308 keV ’ state in 144Sm. . . . . . . . . . . Angular distributions of states in 1383a for which no J" assignment could be made from this work. Spins of 5+ and 3+ have been suggested for the states-at 2415 and 2445 keV respectively (Ref. 37). . . . . . . viii Page 87 88 89 90 91 92 93 Figure 13. 14. 15. 16. 17. 18. 19. Page Angular distributions of states in 144Sm for which no J1r assignment could be made from this work. The state at 3123 keV has been assigned J“=(7i) in Ref. 11 . . . 94 Comparison of results of shell model cal- culations discussed in Sec. IVA with experimentally known energy levels in 1”Be . 95 Comparison of results of shell model cal- culations discussed in Sec. IVA with experimentally known energy levels in 144Sm . 96 Results of collective model calculations for inelastic scattering on 1333a. The Optical model parameters given in Table 2, Set SII were used, and both the real and imaginary parts of the Optical model were deformed. The calculations shown are for the lowest 2*, 3’, 4+ and 6+ states . . . . . . . 97 Results of collective model calculations for 44Sm. The Optical model parameters given in Table 2, Set SI were used, and both the real and imaginary parts of the Optical model were deformed. The calculations shown are for the lowest 2*, 3‘, 4+ and 6+ states . . . . . . . . . . . . 98 MicrosCOpic model DWBA calculations f r the inelastic scattering to the 2 , 41 and 6: states in 1388a. The calculations are i entical except for the wave functions; the left hand column employed the A=136-l40 set while the A=136-145 set was used for the right hand column. Both sets of wave functions predict very similar angular distributions . . . . . . . . . . . 99 Microsc0pic model DWBA calculations for the inelastic scattering to the 25, 45 and 63 states in l33Ba. The calculations are. identical except for the wave functions; the left hand column employed the A=136-140 set while the A=136-l45 set was used for the right hand column. These calculations indicate that the A=l36-l40 set of wave functions provides the better description of the low lying states in 388a. . . . . 100 ix Figure 20. 21. 22. 23. Page Transition densities for the 2+ 2, 4; 2 and SI 2 states in 1338a calculate 'with both sets of wave functions. The 2:, 4i and GI densities are very similar, and predict very similar cross sections. The differences in the 23, 42 and 65 cross sections are directly related to the differences in the transition densities for these states . . . 101 C mposition of the 6; transition density in 1 Ba, calculated with both sets of wave functions. The left hand figure is cal- culated with the A=l36-140 set while the right hand column is calculated with the A=136"145 Set 0 o o o e o e e o o o 102 MicroscOpic model DWBA calculations for I inelastic scattering to the 3i and 5+ states in 1333a calculated with the A=l36-1 0 set of wave functions. The two-body force included central, tensor and LS terms, but no collective enhancement was included. Only the Direct + Exchange calculations are shown . . . . . . . . . . . . 103 MicrosCOpic model DWBA calculations for the inelastic scattering to the 21 2, 4i,2 and 61 states in Sm calculated with the A=136-145 set of wave functions. The inadequacy of the basis space is demonstrated in the calculated angular distributions for the 25, 4g and 6; states . . . . . . . 104 I. INTRODUCTION The recent interest in the N=82 nuclei stems from a number of sources.‘ Foremost among these is the observa- tion that in a shell model picture, low-lying states in these nuclei are expected to be formed predominantly from proton configurations, the neutron shells being closed with (1-2) 82 neutrons. Experimental evidence from proton and neutron(3-5) transfer experiments confirm this expectation. Both proton stripping and pickup reactions on the N=82 nuclei populate only the lg7/2, 2d5/2' 2d3/2, 331/2, and lhll/Z single particle orbitals, thus indicating that proton orbitals other than these do not play a significant role in the wave functions for states of these nuclei. Neutron pickup reactions indicate that the orbitals above the last filled neutron major shell are empty, and con- versely, neutron stripping reactions populate only the orbitals above the closed major shell, thus indicating that neutron shells below this are filled. The picture of the N=82 nuclei which emerges from these experiments is that of a closed 82 neutron, 50 proton core, with low-lying states in these nuclei being formed by couplings of various numbers of valence protons in the aforementioned orbitals. The single particle nature of these nuclei has been thoroughly studied with the proton and neutron transfer reactions described previously. Isobaric analog resonance experiments‘s) have been used to determine, among other things, the positions of the low-lying neutron particle- hole states, which signal the breakdown of our model. Electromagnetic decay aspects of the N=82 nuclei have been (9) (n,n'y)(lo) and measured through (8,7),(7-8) (n,y), (a,an)(;1) studies. These studies have been useful in making precise energy level assignments, as well as often limiting the possible J"r assignments to a few values. The (a,xny) studies have led to the observation of a series of isomeric 6+ states in the even-even N=82 isotones. Charged particle inelastic scattering studies have been limited mainly to the observation of the strongly excited states. Early inelastic scattering experiments‘lz) determined the positions of the first collective 2+ and 3- (13) states. The (p,p'y) and (d,d'y) reactions on the even- even isotones were performed in an attempt to lOcate the positions of excited 0+ states in these nuclei by observing the E0 conversion eleCtrons emitted in the transition to 139 ,)'(l4) the ground state. More recently, the reactions La(a,q 140 (14) 141Pr(a’a.)’(15) 138 a,)'(16) SmiPIP'): Ba(a, l4 Ce(a,a'), 144 (17) 144 (17) Smis,s'), and 4Sm(h,h')(18) have been used to study the collective nature of the strongly excited states in these nuclei. The angular distributions obtained from the latter five reactions were analyzed (19) with the standard collective model formalism and from that work J1r assignments were made, and deformation 139 140Ce experiments parameters BL extracted. The La and have also been analyzed with the collective model approach, and in addition, microscopic calculations have been per- formed using a Gaussian two-body interaction and zero-order pseudo-spin orbit wave functions to describe the nuclear states. However, since alpha particles are strongly absorbed near the surface of the nucleus, only the tails of the wave functions are important and this reaction is thus rather insensitive to the details of the wave functions. In this paper we present results from inelastic proton scattering experiments performed at a bombarding 138 144 energy of 30 MeV on Ba and Sm. Use of the high resolution system developed at Michigan State by Blosser, (20) resulted in a total energy resolution for the 9.2.2;- inelastic peaks of typically 7-10 keV FWHM. Excitation energies accurate to 2 keV were extracted and found to be in good agreement with those obtained by other methods. Using empirical characteristic shapes derived from angular distributions to known states, we assign spins and parities to the majority of the observed states. Most previous microscopic DWBA calculations for inelastic scattering have been restricted to regions of (21,22) the periodic table where particle-hole or simple (23,24) shell-model wave functions were adequate for the desoription of the nuclear states. A second aspect of this work, in addition to spectroscopy, was to attempt to determine if large basis shell model wave functions can account for (p,p') measurementszon nuclei with several valence nucleons. To this end, we have modified the Oak Ridge-Rochester shell-model codes(25) to calculate the necessary structure amplitudes in a form convenient for DWBA calculations. By using two sets of shell-model wave (26'27) in the DWBA calculations for 13888: we functions show that inelastic proton scattering provides a sensitive test for these wave functions, and allows us to choose one set as preferable to the other. Information concerning the structure of the wave functions can be extracted by a detailed consideration of the resulting transition densities. Use of a model proposed by Atkinson and Madsen,(28) and McManus(29) for including effects due to excitations of nucleons out of the core enables us to extract information concerning the polarization charge of the nucleons in this mass region. In Section II we describe the experimental details. of this work, followed in Section III with an individual discussion of all states observed up to Ex=3’3 Mev, and assignments of excitation energies and spin-parities, where possible. Section IV is a discussion of the shell model calculation which we use in this work, and Section V presents thecptical model parameters we obtained from our elastic scattering. Section VI outlines the relevant aspects of the DWBA theory used to analyze our angular distributions, and lastly Section VII is a discussion of the results of this experiment. II. EXPERIMENTAL A. Proton Beam and Particle Detection The measurements were made with a 30 MeV beam of protons from the Michigan State University sector focussed cyclotron. An Enge split-pole spectrograph was used to detect the scattered particles. The amount of beam.on target was monitored both with a current integrator in conjunction with a Faraday cup, and with a 5 mm thick silicon detector placed at 60° with respect to the incident beam. A set of removable slits located immediately prior to the spectrograph scattering chamber was used periodically to check the position of the beam on target. The typical size of the beam spot was 2 mm.high by 4-5 mm wide. ”The entrance aperture of the spectrograph was 2° wide by 1.60 high, corresponding to a solid angle of 0.98 msr. During data accumulation this entrance aperture was the Only slit between the cyclotron and the focal plane of the spectra-3 graph. The absolute energies of the proton beams were obtained from NMR calibrations of the transport system magnets. The uncertainty in this absolute scale was 10.1%. The absolute beam energies far this experiment were 29.8 MeV 138 144 for Ba and 29.9 MeV for Sm. Angular distributions for elastic scattering and for scattering from the strong first 2+ and 3- states in both nuclei were measured using a 300 micron thick solid state position sensitive detector mounted at the focal plane 30 Signals proportional to E, the total of the spectrograph. energy loss of the_particles passing through the detector, and xE, where x is the position along the detector, were analyzed for the type of particle and its location along the detector using a two dimensional data taking program.31 The xE signal was divided by the E signal, and energy vs. position spectra were displayed on a storage scope, where suitable lines were drawn defining the proton band. The computer then identified all events falling between the lines as proton events and stored them in a position spectrum. The resolution obtained with the position sensi- tive detector was typically 30 keV FWHM. Its charge collection efficiency was mapped bygridding the peak from the elastically scattered particles across its surface in 3 mm steps. During data accumulation, the particles to be detected were positioned in a region which had been deter- mined to have uniform efficiency. The remainder of the inelastic scattering data were measured with Kodak NTB 25 or 50 micron nuclear emulsions placed in the focal plane of the spectrograph. Aluminum.absorbers were used to stop all particles of greater stopping power than protons. Emulsions were exposed every 138 5° between 20° and 80° for Ba and from 12° to 95° for 144Sm. Two exposures were made at each angle, a short exposure to obtain data from the first 2+ and 3- states (for normalization purposes), and a sufficiently long exposure to obtain data with good statistics for most of the remaining states. The agreement between the position sensitive detector data and the emulsion data for the 2+ and 3- states was within statistics, so the data were averaged to obtain angular distributions for these states. B. Preparation of Targets Isotopically enriched compounds of Ba(N03)2 (99.8%) and Sm203 (95.1%) obtained from Oak Ridge National Laboratory were used in the fabrication of the targets. The desired compound was placed in a Zr boat and heated in a vacuum, causing reduction of the compound to the enriched metal and simultaneous evaporation of the metal onto the target backing, which consisted of a 20 ug/cm2 carbon foil plus a 3-5 ug/cm2 layer of formvar supporting the carbon. The target material was evaporated over a surface 5/8" in diameter and appeared to be quite uniform. Typical target thicknesses ranged between 50 and 300 ug/cmz. The targets were stored and transferred under vacuum to reduce oxidation. Since complete oxidation occurred in 138 only a few seconds for a thin Ba target, and a few? 144 minutes for a Sm target, thickness was therefore estimated by comparing the measured elastic scattering to optical model predictions for the scattering. The observed contaminants in the targets were carbon, oxygen, magnesium, and silicon, determined from analysis of the inelastic scattering spectrum. C. High Resolution System The emulsion data were all taken using the high resolution system develOped at Michigan State by Blosser, (20) This system relies on dispersion matching,(32) seei- kinematic compensation, and a feedback systemiwhich compensates for possible drift of any magnets in the cyclotron-beam transport-spectrograph system. In a dispersion matched system the line width of the scattered particles at the focal plane of the spectrograph is nearly independentof the energy spread of the incident beam. This is accomplished by using the focussing and dispersive elements of the beam transport system to adjust the disper- sion of the beam on target to match the dispersion of the spectrograph. Kinematic compensation corrects for the change in energy of the scattered particles across the finite entrance slit width, which arises from recoil of the target nucleus. This is accomplished by shifting the kinematic focal plane from its zero order position (position for scattering from an infinitely heavy target nucleus). The approximate beam transport quadrupole settings for 10 dispersion matching and correct position of the focal plane for kinematic compensation are calculated for a given (33) Final minimization of reaction via a computer code. the line width of the scattered protons is accomplished by using a stepped slit and detector device located at the focal plane of the spectrograph and illustrated in Figure 1. Fractional transmission of the elastically scattered protons through the 4 mil slit is maximized (thus minimizing the line width) by adjusting the dispersive elements of the beam transport system and other parameters of the experimental setup. After minimdzation of the line width, this device serves as a feedback system, controlling the spectrograph magnet to keep the elastically scattered protons centered on the transmission slit. This insures that the scattered protons remain at fixed points on the focal plane, independent of drifts in the system. Using this high resolution system we routinely obtained resolutions of ' 7-10 keV FWHM at 30 MeV incident proton energy for the inelastically scattered particles. Figure 2 shows a spectrum l383a at a laboratory angle of 35°, and 144 obtained from Sm obtained at 40°. Typical beam currents on target were 100 na for 1388a (target limited) and 900 na for 144Sm. Figure 3 shows a spectrum from III. EXPERIMENTAL RESULTS 138 144 A. Energies of States in Sm Ba and The high resolution system described in the previous section, in conjunction with nuclear emulsions, was used to obtain precise energies for 20 excited states in 138Ba and 18 states in 144 Sm below Ex=3.4 MeV. Peak centroids and intensities were extracted from the spectra obtained from the scanned emulsions at each angle. This was done with an automatic peak-fitting program, which aided in removing ambiguities in the back- ground subtraction and afforded a consistent method of separating members of close lying doublets. The final adjustments to the basic energy calibration of the spectro- graph were determined by fitting certain strong, isolated peaks in our (p,p') spectra to excitation energies previously determined for these levels by Ge(Li) spectro- meter studies of gamma rays emitted in (8,7) experiments. These calibration energies, along with their errors, are noted in Table 1. This calibration of the spectrograph was then used for interpolatiOn and extrapolation to other excitation energies. These results enabled us to assign an excitation energy to each observed peak at each angle, provided the peak was not obscured by a contaminant. The 11 12 extracted energies were averaged over all angles of observa- tion, and the mean error in the centroid was calculated. 138 144 The energies we have assigned to levels in Ba and Sm, along with the combined random and systematic errors, are listed in Table 1. These energies are in excellent agreement with energies from (8,7) work on 1388a and 144 (a,2ny) work on Sm. B. Angular Distributions Angular distributions have been measured for 18 of the 20 states observed in 1388a and 15 of the 18 observed 144 states in Sm, and for elastic scattering from both nuclei. The elastic scattering angular distributions from 138 144 Ba and Sm are shown in Figure 4. The curves through the data are optical model calculations using parameters (34) The elastic angular distrie of Becchetti and Greenlees. bution data were normalized to the optical model calculations to Obtain an absolute normalization.) A comparison with calculations using other sets of Optical model parametersi35) results in an estimate of 10% uncertainty in the experimental absolute cross sections. Relative uncertainties in our (p,p') cross sections arising from scanning errors, monitor- ing errors and statistical errors are typically 7%. 13 To facilitate a systematic analysis of our (p,p') data we derived from our data empirical characteristic 4. shapes for 2+, 3‘, 4 , and 6+ angular distributions in the following way. Examination of angular distributions for 138 144Sm reveals that the known 2+ states in both Ba and they all have essentially the same shape. Using this fact, one average 2+ shape was obtained from all of the known 2+ distributions in both nuclei. This characteristic 2+ shape was then used as a standard and compared to angular distributions for states of unknown J“. Identical techniques were applied to the angular distributions of all assigned 3-, 4+, and 6+ states in these nuclei to obtain 3-, 4+, and 6+ characteristic. shapes. The resulting +, and 6+ empirical characteristic shapes for 2+, 3-, 4 angular distributions are compared in Figure 5. We emphasize that the characteristic shape for a given J"T is an average of angular distribution data for all known states of that J1r from ngh_nuclei. The states used in the determination of the empirical shapes are noted in Table l. The angular distribution data, along with the characteristic shape of the appropriate J1T which best approximates the data, are shown in Figures 6through 11. The remaining states, whose angular distributions are not similar to any of the charact- eristic shapes, are shown in Figures 12 and 13. They may be grouped into two classes; either they are very weakly l4 excited in this reaction, or they peak farther out in angle than the 6+ states, implying they may be high spin states. As explained in Sec. VIBS, direct DWBA theory would predict L-transfers of 2, 3, 4, and 6 for transitions from a 0+ ground state to states with Jfi=2+, 3-, 4+, and 6+, respectively. There are sufficient differences between the characteristic shapes, as seen in Figure 5, to allow us to uniquely assign an L-transfer of 2, 3, 4, or 6 to the majority of the Observed transitions. This in turn leads to assignments of J"=L, with parity (-)L, if it is assumed that non-normal parity states are weakly excited. In Sec. VIBS we discuss the evidence which indicates that this assumption is valid. For example, an angular distribution for a state of unknown J1r which matches the 4+ character- istic shape has an L-transfer of 4. This in turn leads to a J1T assignment of 4+, and not the non-normal parity 3+ or 5+, as direct'DWBA theory would also allow.‘ Our assignments for the spin and parity of excited 138 144Sm, based on the agreement states we observe in Ba and of the measured angular distributions with the empirical characteristic shapes, are given in Table 1. C. DiscusSion of States in 1388a To organize the discussion of our experimental results, it is convenient to divide the levels which we observe into groups, each group being identified by its appropriate J1r assignment. 15 1. 2+ States (Figure 6) . The states at 1436, 2218, 2639, 3339, and 3368 keV are all in good agreement with the 2+ characteristic shape; we thus assign Jfi=2+ to these states. The state at 1436 keV is firmly established as 2+ from Coulomb excitation,(36) (37) conversion coefficient measurements, and (16) (a,a') inelastic scattering. . The state at 2218 keV is observed to have a strong decay branch (9) to the ground state in neutron capture and (B.Y)(7-8’37) decay experiments. This limits the spin to l or 2. Achterberg, et al.(37) assign positive parity to this state from conversion coefficient measurements. Thus our assignment of J"=2+ is consistent with previous data. The level at 2639 keV, observed in (n,y)(9) and (8,y)(7-8) studies, also has a strong decay branch to the ‘ground state, thus limiting its spin to J=l,2. However, a log ft value of 7.4 for 8 decay from 138Cs given by Carraz, et al.(8) the Jn=3- state of eliminates J=1. The two levels at 3339 and 3368 keV also decay directly to the ground state, limiting their spins to J=l,2. Angular distributions from (16) also suggest a spin of J=2 for (a.a') studies these states. The angular distribution for the state we observe at 3050 keV is not in agreement 16 with the 2+ characteristic shape at forward angles, thus we leave it unassigned. Hill and Fuller(7) assign J=l,2 to this state. 2. 3’ States (Figure 8) 138 The only 3- state we observe in Ba is the one previously assigned‘12'16) at 2881 keV. It is the strongest state in the (p,p') spectrum, and is )(13) and (a,a')(16) strongly populated in (d,d' experiments and in (n,y)(9) studies, where it decays strongly to the 2+ state at 1436 keV. 3. 4+ States (Figure 9) The states at 1898, 2308, 2584, 2779, and 3156 keV have angular distributions which are in- good agreement with the characteristic 4+ shape; we assign J'"=4+ to these states. The level at 1898 keV is eStablished as 4+ from (O,a')(16) angular distributions, (d,3He)(2) measurements which suggest an assignment of 4+ or 6+, and con- (37) version coefficient studies which, when combined with the (d,3He) work, limit the spin to 4+. The state at 2308 keV is assigned Jfl=3+, 4+ from conversion coefficient studies of Achterberg, et al.(37) A J=3,4 assignment has also been suggested by (n,y)(9) and (B:Y)<7) studies based 17 on the strong decay to both the first 2+ and 4+ states. Since non-normal parity states such as 3+ are very weakly excited in inelastic scattering on heavy nuclei, we assign Jfl=4+ to this state, which is also the suggested assignment from (a,a')(16) studies. 7) and Mariscotti, et al.(9) Hill and Fuller< observe a state in the vicinity of the state we see at 2584 keV. Hill and Fuller limit the spin of this state to J=l,2 on the basis of a gamma ray branch to the ground state. However, the angular distribution we measure has a 4+ shape. Thus, we believe there are two distinct levels in this vicinity since the state seen by Hill and Fuller is clearly not a 4+ by virtue of the gamma ray to the ground state, and ours is not a J=l or 2 by virtue of the angular distribution. It isinforma- tive to consider ratios of intensities of two gamma rays depopulating this level, as measured by Hill and Fuller in their (8,y) work and Mariscotti, gt_gl, in their (n,y) studies. I(2583+1436) I + = “708 (nIY) I(2583+l436) _ ‘ 1(258310) ‘ ~2°3 (5'7) (n, ) _ Thus Tag—)- — ~3.3 Similar ratios for the 2583-2218 keV transition relative to the ground state transition are also in the ratio of ~3:1. The non-equality of these ratios can be taken as an indication that the (n,y) and (B,y) experiments are populating twolevels with different intensities in the vicinity of 2583 keV. In addition, Hill and Fuller see a broadening of the gamma ray line connecting their state at 2583 keV with the 2445 keV state. They attribute this to the decay of the 2445 keV to the 2307 keV state, but we suggest this could also be due to a state at 2584 keV decaying to the 2445 keV state. The broadened decay line they observe would then correspond not to two but to three different transitions. We will find in Sec. VIIA that the shell model predicts a l+-4+ doublet near this energy, which would be in excellent agreement with experimental observation. A l+ state would decay to ground via an M1 transition, but since it is a non-normal parity state we would not expect to populate it strongly in (p,p'). The angular distribution we measure for this doublet would then assume the shape characteristic of the 4+ member of the doublet. 19 The state at 2779 keV is observed in (BIY)I(7) )(9) work and decays to both the first but not (n,y excited 2+ and 4+ levels, thus limiting its spin to J=2, 3, 4. It may also correspond to the state at 2.79 MeV in (d,3He)(2) experiments. The state at 3156 keV which we observe is pro- bably not the same state reported by Hill and Fuller(7) at 3164 keV, since the 8 keV difference in energies is well outside the combined errors. However, they assign spin limits of J=2, 3, 4 to their state based on its decay to the first excited 2+ and 4+ states. These two experiments are the only ones which report a state near this energy. 4. 6+ States (Figure 11). We assign Jfl=6+ to the state at 2090 keV, and a tentative (6+) to the level at 2201 keV. Angular distributions for known 6+ states are scarce in the literature. We have obtained an angular distribu- tion for the state at 2090 keV, which has been assigned 6+ by Carraz, et a1.(8) on the basis of its measured half life of 0.8 usec. This assign- ment is consistent with systematics of 6+ states in N=32 DUCIGi; isomeric 6+ states have been identified‘38) in all even-even isotones from 134Te to 146Gd. A + . . a . . 6 a331gnment is also consxstent Wlth the absence 20 of this state in the (n,Y work, and its negligible feeding in the B decay of the 3- ground state of 138Cs. The state at 2201 keV is the subject of some controversy. Carraz, et al.(8) propose that this state has J"=(5-), while Achterberg, gt_§l.(37) propose J"=(4+,5+), based on the measurement of log ft values from the decay of l38““ng and the assumption of Jn=3-, (6-) for the ground and isomeric states respectively of 138Cs. This state is quite weak in our spectra, and not well resolved from the strong 2+ at 2218 keV. Our angular distribution for this state is not inconsistent with any of these tentative assignments. Both the 4+ and 6+ characteristic shapes are drawn through the angular distribution for this state in Figure 11. We would favor a (6+) assignment for this state, based on the predictions of shell model calculations, and to some extent, on the shape of the angular distribution. 5. Other States (Figure 12) We make no Jfl'assignments for the states-we. observe at 2415, 2445, 3254, and 3285 keV. The transitions to these states are all very weak, the largest cross section at any angle being less than 21 10 ub/sr. Achterberg, gt_gl.(37) have assigned J =3+ to the state at 2445 keV, based on angular correlation and conversion-coefficient measure- ments. They also suggest a JTT=5+ assignment for the state at 2415, based on log ft values of the l3Bm'ng. Our angular B decay feeding it from distributions for these states, by virtue of their magnitude, support non-normal parity assignments. The two remaining states at 3254 and 3285 keV are not seen in previous work on this nucleus, and our angular distributions do not shed any light on possible J1T assignments for them. The 2929 and 2990 keV states which were observed only at one angle are very weak and are therefore not likely to be low spin normal parity states. Hill and Fuller(7) suggest spins of J=l,2 and l,2,3,4 respectively for these states. D. Discussion of States in 144Sm 1. 2+ States (Figure 7) We assign Jfl=2+ to the states at 1661, 2423, and 2800 keV. The 1661 keV level is the first 144Sm; its J1T is firmly established (39) :Y) (40) excited state in studies and from Coulomb excitation, (B (a,a') and (p,p')(l7) experiments. Barker and (17) Hiebert observe a 2+ state at 2.45:0.02 MeV 22 via (p,p') and (a,a') reactions which we assume corresponds to our level at 2423 keV. The state at 2800 keV has been assigned Jn=2+, from comparison of its angular distribution with the 2+ character- istic shape. It has also been observed weakly in (40) 144 the 8+ decay of the 1+ ground state of Eu. 2. 3_ States (Figure 8) We assign J"=3_ to the states at 1811 and 3227 keV. The state at 1811 keV is well established to have J =3- from (ara') and (p,p') experiments,(l7) and is the strongest state observed in our 144Sm spectra. The angular distribution of the previously unobserved state at 3227 keV is very similar to that of the 1811 keV state, as well as the angular distri- bution for the collective 3_ state in 1388a. On this basis we assign the 3227 keV state Jfl=3-. 3. 4+ States (Figure 10) We assign J"=4+ to the states at 2191, 2588, 2883, and 3020 keV on the basis of agreement of their angular distributions with the 4+ character- istic shape. The level at 2191 keV has previously been assigned Jfl=4+ on the basis of gamma ray (38) systematics, and recent (a,a') and (p,p') (17) experiments verify this assignment. We asSume that this is the level at 2.21:.02 uev observed in 23 (13) The states at (d,d') and (p,p') studies. 2588, 2883, and 3020 keV have not been previously reported. They are in good agreement with the characteristic 4+ shape, with the possible exception of the 3020 keV state, which falls off somewhat too rapidly for angles larger than 50°. These 4+ assignments are consistent with the fact that Kownacki, gt_al,(ll) have not observed these states 14 144 in the 2Nd(a,2n) Sm reaction which preferentially populates states with Ji8. Studies of the B decay 144 (40) alSo show no of the Eu 1+ ground state evidence for levels at these energies, which is in agreement with our 4+ assignments since population of 4+ states via this decay would be unique second forbidden. 4. 6+ States (Figure 11) The Stockholm group(38) has assigned the state at 2324 keV a spin-parity of 6+, based on its life- time of 0.88 usec. This agrees with systematics of 6+ states in the N=82 nuclei. However, our angular distribution for this state is only in qualitative agreement with the characteristic 6+ shape due to the rise of the data at forward angles. This could be due to a very close-lying low spin. state which would cause the experimental angular 24 distribution to rise at forward angles. This possibility is weakly supported by the fact that the FWHM of this peak is consistently 10-15% larger than that of other nearby peaks. We also assign Jfl=6+ to thegreviously unobserved state at 3308 keV on the basis of the shape of its angular distribu- tion. 5. Other States (Figure 13) We make no J1T assignments for the states we observe at 2826, 3123, 3196, and 3266 keV. The state at 3123 keV has been assigned 7(1) by the (11) Stockholm group in their search for high spin 142Nd(a,2n )144Sm reaction and states using the coincidence techniques. Our angular distribution for this state is consistent with a high spin state; if this is the same state seen by the StOckholm group, we would favor a 7- rather than 7+ assign- ment. The angular distributions for the levels at 2826 and 3196 keV peak far out in angle, suggestive of a high spin state, but the Stockholm group does not place any levels at these energies. The 2800 (2+) and 2826 keV levels are seen as a doublet (17) in the (d,d') and (PIP') work of Barker and Hiebert. We also note the similarity of the 3123 and 3196 keV 25 angular distributions, which leads one to doubt that they are both doublets. The state at 3266 keV has not been observed previously, and is excited very weakly in the present experiment. The angular distribution for this state does not allow us to make any suggestions for its spin and parity. IV. N=82 WAVE FUNCTIONS A. Conventional Shell Model As discussed in the Introduction, we have used large basis shell-model wave functions to describe the nuclear states involved in the present experiment. This section describes the details of the conventional shell (ZS-27) which was done with the Oak Ridge- (25) model calculation Rochester shell model code. The basis space for the shell-model wave functions consists of the lg7/2 and st/2 orbits, plus one-proton excitations from this subspace into the 331/2 or 2d3/2 orbits. The two-body interaction between the valence nucleons was parameterized in terms of a modified surface delta interaction (MSDI), with the four single particle energies and the two MSDI parameters fixed by fitting to energy levels of known J1T in the N=82 nuclei. Two Hamiltonians were calculated. The MSDI para- meters for the first Hamiltonian were obtained by fitting 136 to levels of known J1T in N=82 nuclei from Xe through 145Eu(A=l36-l45), while those for the second Hamiltonian 136 were obtained by fitting to levels from Xe through l4OCe(A=136-140). The A=136-l45 interaction was applicable 26 27 138 144 . to both Ba and Sm, while A=l36-140 was designed for the lower mass N=82 isotOnes, and hence was used only for 138Ba. Thus two sets of wave functions were calculated for 1388a, but only one set for 144Sm. The basis space was the same for all calculations; only the parameters of the Hamiltonian differed. The basic difference between the two Hamiltonians is the 97/2-d5/2 single particle energy splitting, which increased from 500 keV for the A=l36-l45 interaction to 900 keV for the A=136-l40 interaction. It is found that the eigenvalues and eigenvectors calculated with the A=136-140 interaction yield better agreement with experiment- ally known spectra, pickup and stripping Spectroscopic factors and electromagnetic data for the lower N=82 isotones than do those calculated with the A=136-l45 interaction. In particular, the A=l36-l40 calculations are in excellent (27) 1335b and 134Te, the agreement with recent data on one and two proton N=82 isotones, although levels from these nuclei were not included in the search procedure which fixed the parameters of the Hamiltonian. It is reasonable that the A=l36-l45 Hamiltonian might give poorer results for the lighter N=82 isotones. For.the upper N=82 isotones, the effects of the limited basis space appear to be important. 144 For example Sm, which has 12 valence protons, effectively has a basis space consisting of two holes in theg7/2-d5/2 28 orbits and one-particle excitations out of these orbits. 144 The physical low-lying states of Sm presumably have substantial amplitudes in their wave functions for con- figurations outside of the allowed basis space, such as 2 2 2 . (1h , (2d3/2) and (331/2) . Including these states 11/2) in the searching procedure which determines the parameters of the A=136-l45 Hamiltonian could well distort the para- meters to compensate for components outside of the basis space. This would in turn decrease the accuracy of the calculations in the lower isotones. In light of this, 138 the superiority of results calculated for Ba with the A=136-l40 interaction over those calculated with the A=136-l45 interaction is expected. Moreover, it is expected that the best results calculated for 138Ba should be superior to the best for 144Sm, since the basis space is more complete for A3140 . We have used both the A=136-140 and A=l36-145 sets of wave functions in the DWBA calcula- 138 tions for Ba, to see if inelastic proton scattering can identify one set of wave functions as definitively better than the other. Only the A=136-l45 interaction was used in the 144Sm calculation, as previously noted. With the 138 basis space used in this calculation, states in Ba have between 50 and 220 components in their wave functions, while states in 144Sm have between 10 and 45 components. The notation used to discuss the different states will be J1, where i refers to the first or second excited state of spin and parity J". 29 B. Other Structure Calculations Properties of the N=82 nuclei have also been calculated by methods other than the conventional shell model approach of Wildenthal.(26) Rho‘41) performed a two-quasiparticle calculation for the even N=82 nuclei, employing a Gaussian form as the residual nucleon-nucleon interaction. At the time of that work, the single particle energies needed in the calculation were not experimentally known. The results of this calculation are in qualitative agreement with experiment, but no 0+ or 6+ levels were calculated. In a later calculation, Waroquier and Hyde‘42) used an approach similar to Rho, but employed the inverse (43) to obtain the single particle gap equation technique energies for their calculation. In addition theycalculated the 0+ and 6+ states and in general obtained good agreement with existing data. Comparisons of their calculated energy levels and those of the conventional shell model which we use in this work are given in Ref. 42. A new coupling scheme, developed by Hecht and Adler,(44) and employed by Baker and Tickle,(l4) Baer, et al.(15) and Jones, et al.(2) in their work on N=82 nuclei, predicts energy levels in good agreement with our 138B experimental results for a. This pseudo spin-orbit coupling scheme takes advantage of the fact, observed in (26) the shell-model calculation, that for the N=82 nuclei each group of levels with seniority v has some of these 30 levels depressed in energy. Calculations performed<2> with this coupling scheme and using a basis space very similar to that of Wildenthal result in wave functions with at most 23 components. It is encouraging that this scheme, with its apparent simplicity, is able to reproduce the salient features of the conventional shell-model which we have. employed in this work. A comparison of the energy levels predicted by the pseudo spin-orbit scheme and the con- ventional shell model are given for $38Ba in Ref. 2. This coupling scheme also predicts approximate selection rules for relative strengths of excited states observed in inelastic scattering. This will be discussed further in Sec. VIB5. V. OPTICAL MODEL Essential ingredients in any BWBA calculation are the optical model parameters which describe the elastic scattering in the entrance and exit channels. A number of optical model parameter studies(34_35’45) have been made for 30 MeV protons incident on nuclei with A between 40 and 208. From these parameterization studies, formulae result which allow one to interpolate the "best fit" parameters to nuclei and energies other than those specifically used in the studies. However, there is a large gap from tin (A~120) to lead (A:208) for which very little precise elastic scattering data exists, and thus no information for the region was included in the optical model studies. It was not clear, therefore, that the parameters which these studies predict would properly account for the elastic 138 144 scattering from Ba and Sm. Fortunately, parameters predicted by two previous (34-35) studies yield results which are in very_good agree- ment with our elastic scattering data. The optical model parameters of Becchetti and Greenlees<34) 138 predict an elastic l4 scattering angular distribution for Ba( 4Sm) which results in a chi square per point between theory and 31 32 experiment of 3.4 (5.3), while Set II from Satchler's (35) yields a fit with xz/N=4.0 (6.0). As discussed analysis previously in Sec. IIIB, these excellent theoretical fits allowed us to normalize our elastic angular distribution data to theory in order to obtain absolute cross sections for the inelastic scattering data. After this normalization was determined, the predicted parameters were allowed to vary in a search to obtain the optimum parameters for use in the DWBA calculations. The optical model potential used in our analysis has the usual form V(r) = -VR(l+exR) - i(Wvol 4Wsurf d:IM)(1+ IM)-l + (Eq. 5) UfM’Oi 21m 3h3 k C P h 1‘- °i 37 l. ci, of are the helicities of the incoming and outgoing particles, respectively. 2. M is the helicity of the residual nucleus. 3. k1, kf are the momenta of the incoming and outgoing particles, respectively. A target nucleus with spin zero ground state is assumed, and the final state of angular momentum J is described by a particle in orbital jp and a hole in orbital jh. v is the two-body interaction between the projectile and target nucleons. The quantity ZgTj h P for the transition and contains all of the nuclear is the spectroscopic amplitude(51) structure information needed to describe the initial and final states of the target nucleus. A full description of the helicity formalism is given in Ref. 50. 2. Spectroscopic Amplitudes The spectroscopic amplitudes qu th P major interest in this paper. The procedures used are of to calculate these quantities depend upon the model used to describe the states of the target nucleus. In this work the target states are described by the large basis shell model wave functions described in Sec. IVA. We have modified the Oak Ridge— (25) Rochester shell model codes to calculate the 38 spectrosc0pic amplitudes ngj h p for DWBA calculations. The j-j coupling formalism, in a form convenient used by most workers performing DWBA calculations, is more familiar than the helicity formalism pre- viously discussed. The following discussion will therefore be based on notation very similar to that (23) (52) of Satchler and Petrovich. For the direct term of the scattering amplitude, the spectroscopic amplitudes are related to the single particle matrix elements defined by Satchler.(23'24) JIJ H!) J? p T Q . T O U : T U . _ [ML(3p3h)5s,o + NLlJ(3p3h)53,1]‘MLSJ(3p3h) 3 . F l 1 JT . 1 . l * .. _. * (ETTa’Tb Talzrb>tszjh <£pjp§J[TLSJ(8,¢,g)1j|£hjh§> (Eq. 6) where T is the spin angle tensor, and 1 is the LSJ isospin Operator. 3. Elements of the DWBA Formalism (Direct Amplitude) The transition density can now be defined LSJ,T _ f T I I F - . . (j j )u (r )u (r ) (Eq. 7) (r1) Jpjh MLSJ p h nplp l n 2 l h h where un£(r) are the bound state wave functions of the active valence particles. We use harmonic~ 39 oscillator wave functions for the bound state, with the oscillator parameter given by 45 25 hm = —I7§-- -§7§- (Eq. 3) A A LSJ,T The form factor G for the direct term of the (r) 0 scattering amplitude is related to the transition density through the relation Gfiing = (FiiifT LT(r0’rl) Ii drl (Eq' 9) th where ViT(ro,rl) is the L multipole in the decomposition of the two-body force between the bound nucleon and the incident projectile. The LSJ,T (r0) information which describes the states of the target form factor G thus contains all of the structure nucleus, as well as the information concerning the form of the interaction between the projectile and target nucleon. The form factor G?::)T the incident and exit channel optical model wave is then folded in with functions, and squared to get the direct contribution to the DWBA cross section. It is clear from the previous discussion that the magnitude and the shape of the angular distribution is dependent on 1) the Optical model parameters which describe the 4O elastic scattering from the target nucleus, 2) the form.of the two-body force between the projectile and target nucleons, and 3) the transition density. We now consider these elements of the cross section in turn. The procedure for determining the optical model parameters is well defined. The various parameters of the optical model are adjusted until one obtains the best fit to the measured elastic scattering from the target nucleus, as was discussed in Sec. V. The form of the two-body force is, however, not well defined. The most desirable two-body force to use would be one which describes two-nucleon scattering, such as the Ramada-Johnston potential.(53) However, due to its hard core, this potential cannot be used in its original form. A common technique is to apply the Scott-Moszkowski separation method(54) to the attractive-even state components of the Hamada-Johnston potential, and neglect the odd state parts on the basis that they are much weaker than the even state components. This results in an even state force similar to the Serber force. This (24) approach, used by Love and Satchler, results in a potential which retains the basic features of the 41 original potential at low energies and is usable in inelastic nucleon-nucleus scattering calculations as well as in bound state calculations. Petrovich, et al.(55) w Kallio-Kolltveit have used a similar approach with the (56) interaction as the effective interaction and they find that this realistic force gives a good account of proton scattering from 12C and 40Ca. Other often-used interactions have Yukawa or Gaussian radial shapes with strengths and ranges chosen to reproduce low energy nucleon-nucleon scattering data. Comparisons between these various interactions are given in Ref. 24. Many different exchange mixtures other than the Serber mixture have been used in nuclear structure calculations. Often they have large odd-state components, thus differing quite sharply with the forces predicted by realistic interactions. We have tried seven of the more commonly used structure forces(57) to see how their predictions for inelastic scattering compare with those for the central force which we use in this work. This force is an even state Yukawa force with a range of 1.4 F, and a strength chosen to be consistent with a recent (58) The survey of inelastic scattering analyses. results of this study will be presented in Sec. VIICZ. 42 For a zero range force, it is clear from Eq. 9 LSJ,T (r0) the transition density. As the range of the two- that the form factor G is given by r2 times body force increases, the form factor continues to reflect the radial shape of the transition density LSJ,T (r1) defined element in the cross section, namely, the F .' This brings us back to the least well transition density. 4. Transition Density Referring back to Eqs. 6 and 7, we see that this quantity is determined by the wave functions which describe the states cf the target nucleus. At this point it is useful to present a short review of the properties of single particle wave functions u which occur in the transition density. In this n1 work we use harmonic oscillator wave functions, hence the single particle wave functions are completely specified by the principal quantum number n and the orbital angular momentum 2. The quantum number n specifies the number of nodes in the wave function; we use the convention that n starts from 1. We recall from Sec. IVA that the single particle orbitals which form the shell model basis are the 1g7/2, ZdS/Z’ 2d3/2, and 331/2. The single particle 43 wave functions of interest in this work are therefore u14, u22, and “30’ which have 1, 2, and 3 nodes respectively. The transition density will be constructed from a sum of products of single particle wave functions, each product being weighted . T . . . . . by the appropriate MLSJ(jpjh), which in turn is dependent upon the spectroscopic amplitude ng. . 3 It is clear that a term such as u14ul4 in theh p sum will contribute an unstructured shape, while a term such as uzzu3O will have a very structured contribution. An example of a typical transition density is that for the transition to the 2: state 138 in Ba. It is given by F202'° = -o 339u u +o l35u u -o 089u u +0 031u u (r1) ° l4 l4 ' 14 22 '.. 22 22 ° 22 30 The coefficients Mg02(jpjh) are determined by the wave functions for the 03.3. and 2: states. Different.wave functions will give different coefficients, and thus a transition density of different shape. This will in turn modify the shape of the form factor, and also the cross section, as discussed earlier. The magnitude of each MESJ(jpjh) is related to the coherence properties of the amplitudes of the components of the wave functions; in general 44 k a larger MESJ(jpjh) will imply constructive interference between the amplitudes while a small number will imply destructive interference. However, in our case the smallness of the MESJ(jpjh) involving the 2d3/2 or 381/2 orbitals is also in part due to the restriction on the occupation of these levels, as discussed in Sec. IVA. Hence, there are two aspects of the transition density which affect the cross section; the first being the magnitude of the individual components, and the second being the interference among the terms of the sum. Specific examples of transition densities will be illustrated in Sec. VIICl, where we compare the 138Ba calculated with both transition densities for the A=l36-140 and Ael36-145 sets of wave functions. we will find that one can easily distinguish the two sets of wave functions by virtue of the resulting transition densities and the angular distributions which they predict. we note at this point that other methods exist for extracting the necessary transition density. One promising approach is through inelastic electron (59) It can be shown_that the transition scattering. density is simply related to the measured form factor in (e,e'), and high quality (e,e') data over a wide range of momentum transfer can fully determine 45 the proton transition density, since electrons are only sensitive to protons in a nucleus. This can then lead to a determination of the neutron transition density if proper account is taken of core polarization effects. Since 30 MeV prdtons are not strongly absorbed the cross section is sensitive not only to the tail of the transition density and its value in the vicinity of the nuclear surface as in (d,d'), but also to the transition density inside of the nucleus. For this reason, medium energy inelastic proton scattering provides a very sensitive test of the wave functions involved in a transition. The previous discussion has been concerned only with the direct DWBA contribution to the scattering amplitude. The transition density is not defined as such for the exchange amplitude, since for exchange, the bound state wave functions have differ- ent radial co-ordinates. However, a corresponding quantity. to MESJUPjh) for the direct term exists (24) and can be used to obtain for the exchange term, an estimate of the magnitude of the exchange contri- bution to a given transition. In the case of the exchange amplitude, the form factor is different for each pair of partial waves, and involves many 46 multipoles of the two-body force for an orbital angular momentum transfer L. However, it has been found by a number of (24'60-62) that the direct and exchange authors amplitudes are constructively coherent in general, and identically so for a zero-range even state force. Atkinson and.Madsen(28) have done a particularly complete study of the properties of the direct and exchange amplitudes for transitions in single closed shell nuclei (such as the N=82 nuclei). They find that with a Serber force the shapes of the exchange contributions to the angular distributions are very similar to those for the direct term. Since we have also used a Serber force, the previous transition density discussion appears to remain valid when the exchange amplitude is included in the cross section; the main effect of the exchange amplitude being a renormalization of the magnitude of the cross section. 5. Discussion of Selection Rules and Non-Normal Parity States In terms of the transferred orbital angular momentum L, spin S, total angular momentum J and isospin T, the selection rules for the direct amplitude in the DWBA are 47 i f An = (-)L where Aw denotes the change in parity. Both 138Ba and 144Sm have JE=O+, so J=Jf. For the exchange term in the DWBA amplitude, the selection rule A1r=(-)L no longer holds. Thus for exchange, all four triads (LSJ)=(JOJ), (JlJ), (J-l lJ), and (J+l lJ) can contribute to the cross section, while for the direct term, only the first or second pair can contribute. The terms which the second pair cf triads give rise to are commonly referred to as non-normal parity terms and are found in general to be small except in the case of transitions to high spin states, where they- can become non-negligible.(24) . The only experimental angular distributions for non-normal parity states (states for which nf(-)J) in masses A>80 of which we are aware arerthose for 138 the 3+ and (5+) stateszin Ba, which we observe, and an angular distribution for a 4- state in 48 2oapb.(63) In all cases, the cross sections are less than 20 ub/sr at all angles. The fact that so few non-normal parity states are observed in inelastic scattering is evidence in itself that cross sections to such states must be small. In conclusion, both theory and experiment indicate that non-normal parity states (also often referred to as spin-flip states) are very weakly excited in medium energy inelastic proton scattering on heavy nu01ei. As mentioned in Sec. IVB, the pseudo spin- (44) orbit coupling scheme of HeCht and Adler predicts a selection rule for inelastic scattering. This selection rule is based on the assumption that the transition densities are independent of the quantum numbers j jh and depend only on the orbital angular P momentum transfer L. For (d,d') this is a reason- able assumption, since the alpha particles are strongly absorbed by the nucleus and are sensitive to the transition density only at the nuclear sur- face where for the case of N=82 nuclei, the transition densities are quite similar as illustrated in Ref. 14. However, this may not be a good assumption for protons, which are not strongly absorbed. The . selection rule states that AB=O where B is the total 49 pseudospin. For an even number of protons, B ranges from v/2 to 0, where v is the seniority of the 138Ba which we have state. The wave functions for used have mixed seniority, but projecting out wave functions of good seniority reveals that the low- lying J#0 states are more than 80% seniority two states. In the Hecht-Adler scheme, the lowest 2+, 4+ , and 6+ states have v=2, B=0 and transitions to these states from the v=0, B=O ground state are allowed. Our data show them to be relatively strongly excited. The next group of states have v=2, B=l so transitions to these states would violate the AB=0 rule. With two exceptions, Figure 2 shows that the positive parity states between 2.2-3.2 MeV are weakly excited. The third group of states predicted in the pseudo spin scheme are v=4, B=0 states. The relatively strong 2+ states at 3339 and 3368 keV in 138 Ba are perhaps members~ of this group, since the shell model also predicts these levels to be mostly seniority four states. we thus find that the pseudo spin orbit selection rules predict results which are in qualitative agreement with our data. VII. DISCUSSION OF RESULTS In this section we present results of the calcula- tions described in Sections IV and VI, and compare the theoretical predictions from those sections with the experimental results from Section III. A. Comparison of Shell-Model Calculations to Experiment we begin by contrasting the results of the shell 138 144 model calculations fOr Ba and Sm described in Sec. IVA with the experimental energy level spectra obtained 138Ba resulting in Sec. IIIA. The energy level spectra for from shell model calculations with both the A8136-l45 and A=136-l40 Hamiltonians, together with the experimental level spectrum as determined from our measurements, are shown in Figure 14. The calculated energy level spectrum, using the A=136-140 interaction, is in excellent agreement with experiment. There is oneeto-one correspondence between theory and experiment up to 2.9 MeV of excitation, with the exception of the experimentally missing excited 0+ state. Each of the states predicted by theory up to 2.85 MeV are in agreement with their experimental counterparts to within 200 keV, and for most states the agreement is better than 50 51 100 keV. In Sec. IIIC4 we noted that the angular distri- bution for the state at 2201 keV did not enable us to assign this state J"=6+, although a 6+ assignment is not inconsistent with the data, as seen in Figure 11. Compar- ing experiment to theory, one clearly finds additional support for a 6+ assignment to this state. The states at 2415 and 2445 keV, which have been assigned (5+) and 3+ respectively,(37) have structureless angular distributions and are excited very weakly in our (p,p') measurements, thus leading us to concur with the non-normal parity assignments. These JTr assignments are also in excellent agreement with the shell model predictions. Recalling from Sec. IIIC3 the discussion of a l+n4+doublet at 2583-2584 keV, we see such a preposal is strongly supported by predictions of the shell model. In the discussion of Sec. IVA, we indicated that the parameters in the A=136-l45 interaction may reflect deficiencies in the basis space for the upper N=82 isotones, since states of these isotones used in the determination of the interaction parameters may have configurations lying outside the present basis space. We observe from Figure 14 that the A=136-l45 interaction does not reproduce the. 138Ba energy levels with the accuracy of the Asl36-l40 Hamiltonian. The major differences are in the first 4+-6+ splitting, and in the spacing of the levels from 2.3 to 2.6 MeV. A more sensitive test of the relative quality of 52 the wave functions resulting from these interactions is found in the microsc0pic DWBA calculations, which will be discussed shortly. The experimental energy level spectrum for 144Sm along with the predicted energy level spectrum calculated from the Ae136-l45 interaction is shown in Figure 15.. The general characteristics of the experimental spectrum are reproduced; however the specific state-by-state agreement is not as impressive as the agreement between theory and 138 experiment for Ba. Allowing more than one proton excitations into the 351/2 and 2d3/2 orbits, and inclusion of pairs of particles in the lhll/Z orbit would be expected to improve the agreement between theory and experiment. B. Collective Model Results In this section we present the results of a 138 144 collective model analysis of all states in Ba and Sm for which J1r assignments have been made. Figures 16 and 17 show our measured angular distributions for the lowest—lying 138 144 2+, 3-, 4+, and 6+ states in Ba and Sm, along with the collective model predictions for these states. The optical model parameters labeled Set SII(Set SI) in 138 14 Table 2 have been used in the calculations for Ba( 4Sm), but any of the three sets give fits of similar quality. As seen in Figures 16 and 17, the predicted angular distributions 53 are in good agreement with the data for the 2+ and 3- states, but this agreement deteriorates as one goes to the higher spin states. Results of calculations for the remaining states obserVed in our measurements are not shown, since our use of characteristic shapes indicates that all experimental angular distributions for a given J1T are very similar in shape. The empirical observation that the shapes of the angular distributions appear to be independent of excitation energy in the energy range from l-3.5 MeV has been verified through our collective model DWBA calculations. Deformation parameters B£,as discussed in Sec. VIA, have been extracted by normalizing the eXperimental and theoretical cross sections over the angular range of the data. The results of this analysis are given in Table 3. The smallness of these parameters, except for the lowest 3- states, is another indication that the states are not strongly collective. Barker and Hiebert‘I7) have also studied 144Sm(p,p') at 30 MeV, and the results of their collective model analysis are in good agreement with ours for the four states which they observe (see Table 3). In Table 3 we also list the isoscalar transition strengths GL, in single particle units, calculated from Eqs. 2 and 3. we note they are only about one-half the value obtained from Coulomb excitation measurements for the 54 + 21 this mass region, states. This phenomenon persists for other nuclei in (16) which seems to be the only region which does not exhibit equality between the isoscalar and electromagnetic transition rates when they are extracted using this model. C. Microsc0pic Model Analysis As discussed in the introduction, one of the main purposes in undertaking this work was to determine if large basis shell-model wave functions could accurately account for both the shape and magnitude of measured angular distributions obtained from inelastic proton scattering. To this end, we have applied the microsc0pic DWBA theory discussed in Sec. VIB to calculate angular distributions for the 2+, 2:, 4:, 4;, and 6:, 6; states observed in 1388a and 144Sm. The pertinent details of the inelastic scattering calculation are as follows. The Optical model parameters labeled Set SII(Set SI) in Table 2 are used to describe 138 144 the incident and exit channels of Ba( Sm). The bound states are described by harmonic oscillator wave functions, with an harmonic oscillator constant obtained from Eq. 8. The two-body interaction between the projectile and target nucleons was central only, with a Serber exchange mixture and a Yukawa radial dependence. The range of the force S=0 =-804 MeV, PP was taken to be 1.4 F and its strength (V 55 S=O where Vpp is the S=0 part of the proton-proton interaction) was chosen to be the mean of the strengths obtained in a recent survey of inelastic scattering analyses.(58) Core polarization, i.e. the effect due to contri- butions to the cross section from nucleons outside the explicit shell-model basis space, must be included for a (64) In the prOper description of inelastic scattering. case of electromagnetic transitions these effects also appear and are accounted for by renormalizing the charge on the nucleons, i.e., by introducing a "polarization (28) (29) have shown that one charge". Madsen and McManus can similarly correct for finite basis-space effects in inelastic scattering by renormalizing the strength of the two-body force which mediates the transition. Thus One has an "effective force" for (p,p') which is analogous to the "effective charge" for electromagnetic transitions.(65) One can get an idea of the amount of core partici- 138Ba by noting that for pation in the low-lying states of the wave functions used here, the calculated B(E2; 2I+OI) is a factor of 3.2 too small(66) if no polarization charge 6e is used. This implies that (1+6e)2=3.2, or de=0.8. To account for the contribution to the (p,p') reaction of protons excited from the core, one therefore renormalizes the interaction strength V to (1+6e)Vpp. However, neutron PP 56 core excitations also contribute to (p,p') cross sections and are, in fact, more important than those for protons, since the proton-neutron two-body interaction Vpn is stronger than V . If it is assumed, as has been found by Bernstein(67) PP (68) and Astner, et al. that contributions from neutron and proton core excitations are approximately in the ratio of N/Z (the ratio expected in a collective model picture), we need an additional term, N/Z 6e Vpn' For the Serber exchange mixture we use, V =2V . Thus one obtains a Pn PP total ff ct’ f rc of 1+6 V +2N Z6 V = 1+6 1+2N Z V e e ive o e ( e) pp / e pp [ e‘ / )J p i.e. the strength is increased by a factor of (1+6e(1+2N/Z)). I P We use this result in all calculations in this paper. We have also inverted this process and used the measured enhancement factors to extract polarization charges for other 138 transitions in Ba, for which electromagnetic transition data are not available. Calculations of cross sections were performed for the 2:, 2;, 4:, 4;, 6:, and 6; states in 138Ba. The enhancement factors were extracted by normalizing the experimental and theoretical integrated cross sections over the angular range of the data. The results are shown in Column 3 of Table 4 and we see that the 6e are constant within the probable overall uncertainty in the analysis. 138 l. Microsc0pic DWBA Calculations for Ba For 138Ba, we have calculated angular distributions using both sets (A=136-l40 and A=136-l45 Hamiltonians) of 57 wave functions for the aforementioned 6 states. Figures 18 and 19 show the angular distributions predicted by each set of wave functions, together with the apprOpriate data. We see that the magnitudes and shapes of the calculated angular distributions are in good agreement with the data for the 2:, 4:, and 6; states for both sets of wave functions. However, the agreement between theory and experiment for the 2+, 4:, and 6; states is much better for the A=l36-l40 set of wave functions than for the A=l36-145 set, which predicts cross sections which are an order of magnitude low, and also exhibit poorer agreement in shape. From this analysis it appears that the A=136-l40 set of wave functions gives the better description of low- lying states of 138Ba. To find the reason for this behavior, recall from Sec. VIB4 that all of the nuclear structure information entering the DWBA calculation is contained in the transition densities. Thus it is informative to compare their differences in structure as calculated from each set of wave functions. Figure 20 shows such a comparison. The magnitude of the transition density is plotted versus the radial coordinate in units of roA1/3; thus unity corresponds to the nuclear surface. Inspection shows that the transition + densities for the 2:, 41, and 6: states are quite similar for both sets of wave functions. They peak slightly inside 58 the nuclear surface, which is a general characteristic(52) of these quantities. We recall that the cross sections calculated for these states were very similar for both sets of wave functions. However, looking at the transition 4;, and 6; transitions, we note densities for the 2:, distinct differences. The A=l36-l45 wave functions yield transition densities with a pronounced decrease of the surface peaking, and an increase in magnitude of the peak near 0.6 of the nuclear surface, relative to the A=l36-l40 results. For the 6; state, this effect is so great that the transition density resembles that for a much lighter nucleus. Since the transition density (and therefore the form factor) peak too far inside the nuclear surface for this transition, the diffraction pattern predicted by the DWBA is pushed out, as if the target nucleus were indeed much lighter. This is exactly what we observe for the calculated 6; cross section for the A=l36-l45 set of wave functions. We can infer specifically what is wrong with this set of wave functions by considering the individual contri- butions to the total transition density for the 6; state, for example. Figure 21 shows this transition density broken down into its component parts un£=u14 ul4 and ul4u22. The A=136-l40 set of wave functions enhances the ul4u22 term relative to the ul4ul4 term, which results 59 in the surface peaking. However, this enhancement is not present for the A=136-145 wave functions, which results in the transition density being very small at the surface due to a cancellation effect. Tracing back one step farther, we can look at the spectroscopic amplitudes which contribute to ul4ul4 and u14u22 and thus directly study the wave functions. Only the matrix element contributes to ul4ul4, while both the and matrix elements contribute to the ul4u22 term of the sum. Table 5 shows the structure of the largest components of the pertinent wave functions, as well as the individual contributions to the 6: transition density calculated with both sets of wave functions. The two transition densities are thus F606,0 (r1) = 0.1292 ul4ul4 + 0.3223 u14u22 A=136-140 F606'0 (r1) = 0.1765 ul4u14 + 0.1978 ul4u22 A=l36-l45 The quantity of interest is the ratio u14u22/u14u14 which has the value 2.50(l.12) for the A=136-l40 (A=136-145) interaction. The major reason for the smaller ratio from the A=136—145 wave functions is the smallness of the u14u22 term. Even though this set of wave functions has the smaller g7/2-d5/2 single particle splitting and hence would be eXpected to have the larger u14u22 term, a detailed comparison of the wave functions in Table 5 show this is 60 not true. The largest contributions to uuu22 for the A8136-l40 set come from the (g7)5+(g7)5(d5)l and 4 2+ 4 2 (97) (d5) (97) 5) wave functions are much smaller. This arises from the (d amplitudes, which for the A=136-l45 observation that the smaller 9.7/2-d5/2 splitting leads to a fragmentation of the strength of the 6; wave function over many components. Many of these components cannot be connected by the one body (p,p') Operator (a+a) to the strong components of the much less fragmented ground state, and hence do not contribute significantly to the transition density. It thus appears that this decreased mixing between the 97/2 and d5/2 orbitals is the required ingredient in obtaining a reasonable fit to the angular distribution for the 6; state. A similar analysis applied to the transition densities for the 4; states arrives at the same conclusion-namely that there appears to be too much mixing of the 9.7/2-d5/2 orbitals in the higher lying states as calculated with the A=136-l45 interaction. Specifimx information concerning the structure of the wave functions can thus be obtained by analyzing the composition of the transition densities in this manner. Comparing the DWBA calculations result’ A“rom the collective model (Fig. 16) and microscopic moo. .18) for the 2+ state, we see that the collective modeJNa l somewhat better job of fitting the data. This is due shinly 61 to the 2; microsCOpic calculation slipping out of phase with the maxima and minima of the data. We have performed a collective model calculation using the form factor obtained by deforming only the real part of the Optical model potential, and obtained an angular distribution nearly identical to the angular distribution obtained from the microsc0pic model. This implies that if one were to combine the form factor obtained by deforming the imaginary part of the Optical model with the real form factor used in the microscopic analysis, the resulting angular distri- bution would be in as goOd agreement with the data as that of the full deformed collective model. Unfortunately, the computercode we use for the microsc0pic DWBA calculations does not at present have the Option of using a complex'form factor; thus the above conclusion is rather speculative. However, it has recently been found that using a complex microsc0pic form factor results in appreciably better fits (69) and asymmetry(70) data. It to angular distribution would also be interesting to determine if the addition of an imaginary term to the form factor, which appears to improve the fit to the 2:, would destroy the relatively good fits to the 4: and 6: states obtained with the present micrOSCOpic approach. 62 It must be noted that our calculations use a multiplicative constant in the form factor to account for core polarization and the angular distributions take the shape predicted by the purely microsc0pic calculation. Other microsc0pic calculations(64) frequently employ an additive term in the form factor based on the collective model to simulate the effects of core polarization. Often times, using this latter procedure, the collective term is the dominant contributor to the cross section, so the predicted shape for_the angular distribution is in reality due to the collective model contribution. Thus, these "microscopic" calculations achieve good agreement with the data as regards the shape of the angular distribution, due to the fact that collective model predictions for the shape are in general better than those calculated from a purely microsc0pic model such as we have used. 2. Calculations with Other Forces A Serber exchange mixture, which is an even state force, is generally employed in microscopic inelastic scattering calculations. It has been found to contain about the correct exchange strength to give the required enhancement for different L transfers. However, in nuclear structure calculations, many other types of forces have been employed, and we have tried a number of these to see if they give as good a description of the inelastic scattering 63 process as does the Serber mixture. We have made calculations for each of the forces "Cal", "Cop", Clark Elliot I, Ferrell-Visscher, Rosenfeld and SOPer summarized in Ref. 57, all of which contain non-negligible odd-state components. The triplet-even parts of the various forces l=-40 MeV. The range of the TE two-body force, which had a Gaussian radial shape, was have all been normalized to V 1.67 F; this translates into 1.346 F for a corresponding Yukawa radial dependence which we use. The strength of the Serber fOrce is very similar to the strength we have used in the calculations discussed previously. The results are shown in Table 6, along with the results obtained with the Serber mixture. We observe that only the Clark-Elliot I and Soper interactions (which have weak odd state components) yield results similar to the Serber mixture, which reproduced the data. The forces with strong odd-state components cause the direct and exchange cross sections to exhibit the wrong dependence upon L—transfer and in addition, often the theoretical angular distributions acquire shapes which do not resemble the data. We conclude that while such forces may be acceptable for nuclear structure calculations, the strong odd-state components make them inadequate to describe inelastic proton scattering. 64 we have also performed calculations including tensor forces, consistent with OPEP(58) and find that the tensor force contributions to the cross section are at most 7%, and this is for the 6+ states, where the non-normal exchange amplitudes are becoming non-negligible.(24) The spin-orbit force may be important‘7l) for the 6+ states, and this possibility is being investigated further. In addition, we have calculated angular distributions for the non-normal parity 3+ and 5+ states, using only the A=136-l40 set of wave functions. Such states are not expected to be enhanced due to collective effects, but should be sensitive to the tensor and LS forces. The pre- dicted cross sections calculated with central,and central plus tensor plus LS forces obtained from the Hamada Johnston potential and given in Ref. 58, are presented in Figure 22, along with the data. The enhancement due to core polariza- tion is not included, and the direct plus exchange calcula- tions underestimate the data by a factor of 3-5 for the central plus tensor plus LS force. 144 3. MicrosCOpic DWBA Calculations for Sm Only the A=136-145 Hamiltonian was applicable to 144Sm, so only the set of wave functions corresponding to this interaction was employed in the DWBA calculations. The results are shown in Fig. 23. The D+E angular distribu- tions for the 2: and 4: states are a factor of two smaller 65 than the data at forward angles, while the 6: calculation is not in good agreement with the experimental distribution. However, we recall from Sec. IIID4 that this state is possibly a doublet, which would make any theoretical conclusion based on this state tenuous at best. The underestimation of the magnitude is undoubtedly due in part to the restricted basis space in which the shell model calculation was performed. This inadequacy of the basis space is clearly pointed out when one considers the calculation for the 2; state. All of the strength has been concentrated in_21, causing the angular distribution for the 2; state to fall a factor of 25 below the data. In addition? the shape is not qualitatively correct; the maxima at 40° is larger than the first at 20°. The calculated 4: angular distribution is a factor of73 lower than the data, while the calculation for the 6; bears no resemblance to the data. This can easily be predicted from observation of the transition density for the 6; state; it is negligible at the surface of the nucleus. All of its strength is concentrated around 0.6 of the nuclear radius, as in the similar case for the 6; transition density in 138Ba calculated with this set of wave functions. Most 144Sm microsc0pic calculation is the disturbing about this fact that a constant polarization charge does not reproduce the magnitude of the angular distribution for different 66 L-transfers. One is required to use a state dependent polarization charge, whereas a state independent charge 138 . (65) was found to be adequate for states in Ba However, we feel this also is a manifestation of the limited basis 144 space for the Sm shell-model calculation. VIII. CONCLUSION High resolution medium energy inelastic proton scattering has been shown to be an effective method for «:btaining precise information concerning the excited states (of a nucleus. We have obtained excitation energies for levels in 138 ‘wwr‘““*+—flm-r Ba which are in excellent agreement with previous gamma ray work on this nucleus, and in addition. ‘we.are able to reduce the uncertainty on previous spin- parity assignments, and in most cases suggest an absolute assignment. We have increased the number of known levels up to Ex=3.4 in 144 Sm from 8 to 18 and suggested spin- parity assignments for the majority of these states. The experimental information concerning the levels up to 138 144Sm has been reviewed, and found Ex=3.4 MeV in Ba and to be in good agreement with recent shell model calculations for this region. Collective model DWBA calculations have been carried out for both nuclei, using a form factor obtained by deforming the real and imaginary parts of the optical model potential. The results were analyzed using the formalism of Bernstein to obtain estimates of the strengths of the corresponding electromagnetic transition rates. 67 68 MicroscOpic DWBA calculations including the exchange amplitude were performed for the 2; 2, 4: 2, and 6; 2 states I I I in 1383a and 144Sm, using shell model wave functions(19-20) and a realistic two-nucleon force. The necessary structure amplitudes were calculated with a modified version of the Oak Ridge-Rochester shell model code. In the case of 138Ba, two sets of shell model wave functions were calculated, and it was determined from the DWBA calculations that inelastic proton scattering clearly distinguished one set as superior to the other. With this result the transition densities, which provide the link between the wave functions and the DWBA reaction model, were then analyzed to see if one could determine the undesirable properties of the poorer set of wave functions. 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Letters 35B, 371(1971). i APPENDIX A TABLES 74 ;,| 75 Lble 1: Energy Levels of 138Ba and lem. 1388a _ . .. ‘ w 1““5111 resent Work Previous Work Present Work Previous Work BXEJflla’d EXEJ’H" EXEJMaéd ._ Excmc i838g 11.0 2* 1835.7 2* 18813*11.0 2* 1880.811.0 2* 1898g*11.0 8* 1898.810.3 8* 1811g 11.2 3' 1810.1 3‘ 2090g*1l.0 * 2090.110.8 <8)* 2191g*11.0 8* 2190.811.0 8* 2201 12.0 2203.2f 2328e 11.0 2323.2 8* 2218 11.0 2* 2217.9 2 2823* 11.0 2* 2823.811.0 2308* 11.0 8* 2307.810.3 (3,8) 2878 11.9 2878.3 0* 2815 11.2 2818.9 (5*)h 2588 11.0 8+ 2885 11.2 2885.8 3* h 2881 11.8 2582.8 1,2 2800 11.8 2* 2588 11.0 8* 2828 11.8 2830 2839 11.2 2* 2839.3 2 2883 11.9 * 2779* 11.0 8* 2779.210.5 2,3,8 3020 12.0 8* 2881g 11.2 3' 2880.5 3' 3080 12.0 (2929) 12.0 2931.1 1,2 3123 11.8 3123.8 (2990) 12.0 2990.8 1,2,3,8 3198 11.9 3050* 11.0 3089.911.0 1,2' 3227 12.0 3‘ 3158 11.2 8+ 3266 12.3 3183.5 2,3,8 3308 12.1 8* 3258 11.2 ‘ '3285 11.8 3339 11.8 2* 3339.5 1,2 3352.2 1,2 3368 11.8 2*” ‘ 3385.9 1,2 a ‘ Excitation energies in keV. From Ref. 7, except see (f,h) below. From Ref. 17 and references cited therein and Ref. '40. Subset of levels used in energy calibration is marked with an asterisk (*) . Unresolved doublet whose angular distribution is con- sistent with a spin 6* state plus a lower spin state. From Ref. 8. gUsed in determination of characteristic shapes. From Ref. 37. b 76 Table 2. Optical Model Parameters for 138Ba(luuSm). Adjusted ' Satchler Satchler Becchetti-Greenlees Set SI Set SII Rc 1.25 (1.25) -1.2 (1.2) 1.2 (1.2) VR 53.26 (53.20) 56.80 (56.10) 58.80 (55.16) PR 1.162 (1.172) 1.122 (1.13) 1.1“ (1.139) aR 0.75 (0.75) 0.75 (0.75) 0.75 (0.75) WVOL 3.78 (3.50) 3.0 (2.70) 3.0 (2.65) rVOL 1.32 (1.32) 1.33 (1.33) 1.33 (1.33) aVOL 0.66 (0.615) 0.696 (0.667) 0.672 (0.65) WSURF 6.27 (6.11) 6.49 (6.72) 6.86 (7.09) rSURF 1.32 (1.32) 1.33 (1.33) 1.33 (1.33) aSURF 0.66 (0.615) 0.696 (0.667) 0.672 (0.65) VLS 6.20 (6.20) 6.“ (6.4) 6.1 (6.1) PLS 1.01 (1.01) 1.12 (1.12) 1.19 (1.125) aLS 0.75 (0.75) 0.75 (0.75) 0.75 (0.75) X2/N 1.8 (2.8) 1.8 (1.6) 1.1 (1.8) + OD+E(21) 0.215 ( .212) 0.235 ( .208) 0.229 ( .203) OD+E(N:) 0.0678( .0629) 0.0727( .0613) 0.0717( .0599) OD+E(6:) 0.0831( .0258) 0.0858( .0281) 0.0855( .0237) 5ww~wrr‘fi-v -J 1 not 77 Table 3. Deformation Lengths and Transition Strengths for 138 188 Ba and Sm. 138Ba 188Sm Ex Ex Energy J BLR' G(L) Energy J BLR' G(L) 1838 2 0.83 8.1 1881 2 0.88(0.88)a 8.7(8.8)a 2218 2 0.23 1.7 2823 2 0.29(0.29) 3.5(2.9) 2639 2 0.07 0.2 2800 2 0.18 0.8 3339 2 0.15 0.7 1811 3 0.87(0.82) 38.0(28.8) 3368 2 0.17 1.0 3227 3 0.07 0.3 2881 3 0.75 18.8 2191 8 0.33(0.32) 5.8(8.3) 1898 8 0.31 8.1 2588 8 0.21 2.3 2308 8 0.21 1.9 2883 8 0.25 3.2 2588 8 0.08 0.2 3020 8 p 0.23 2.8 b b 0.11 1.0 2779 8 0.12 0.6 2328 (6 0.18 2.8 3156 8 0.07 0.2 3308 6 0.15 1.8 2090 6 0.26 5.1 2201 (6 ) 0.15 1.7 aNumbers in parenthesis are from Ref. 13. bThese numbers represent the extreme credible fits to the data. sew-cw f -u‘} 78 Table 8. Effective Charges for Transitions in 138Ba. Transition ' Lb) 68¢) 0* 2: 2 0.82 .2 0* 8: 8 0.88 .2 0* 6: 8 0.81 .2 0* 2; 2 0.98 .2 0* 8; 8 1.07 .2 0* (8;)a) 8 0.73 .2 aThis state has not been unambiguously assigned 6+, but its angular distribution, together with the shell-model predictions, suggest this assignment. This is the L-transfer for the dominant amplitude. Non—normal parity amplitudes also contribute to the cross section, and are included in the calculations. See Ref. 28. c . . 2_ Calculated from the relationship [(1+6e(1+2N/Z)] ’Oexp/Otheory is calculated using b where the theoretical cross section otheory the shell model wave functions described in the text. ersrsrrrrmra-Iv . 1-- y ul 79 Il‘l 4. .. ullmrtrut-:umuv msHH.o oomo.o mmsa.o AN\hw_m+m_N\mUv AN\mU_w+m_N\hmv Am\bw_m+m_w\hwv msasmmau¢fiANAmuo3Asmo_H~o.o-AmAmcomAsmv_m:~.o-AHAmvomAsmv_mom.o-AmAswv_msm.o o:H-omHum3 mm paw Mo mo mpcocanoo 90mm: m3HlmmHu< Ojalmmau< II A (D II A (D .m magma 80 mm mmH ._ 1| ‘4]. d . 12...“! .M‘Infi'mr HHN.o :Nm.o 555.0 OHN.o mmH.H me.o Hmm.m mmH.N mmmMMm mmH.o mmw.o QHN.o mmH.o mm:.o omm.o :mm.H omm.H mmmom mmm.H oo.H owm.o 5Hmo.o mmH.o OHH.o moH.o 5m:.o QAMMZMmom m:5.H oo.H :mm.o 5mmo.o HmH.o Hmmo.o HmH.o mmu.o >Im mH:.o 533.0 5w5.o mm:o.o mHm.o Hmmo.o mmm.H 5mm.o Hlmo Hm:.o 5mN.o om:.o m:m.o H:N.o m:m.o mmm.o om:.m moo www.o mmm.o mmH.o womoo.o 05H.o 5H:oo. mm~.o :mmoo. A pom mcompomm mmopo m+a cum 0 mo acmwpmano .m oHnma APPENDIX B FIGURES 81 82 . r 1.1.. . .QGMHQ Hmoom may mGOHm meOHuumm poumuumom mo mmsoum on» no mnucw3 maHH EsEHcHE mcHHaqu man» .m3Mn mmmun on» zoosumn mommmm Econ owuouumom hHHmowumMHm mo ucdoam EdEHxME on» HHucs vmumsnvm mum mumuwamumm HmuamEHuwmxm msa .nmmnmonuoomm man no mGMHm Haven 0:» :« cwumooH Eoummm :oHumN IHHHnmumlcowumNHSHHQOIuamEmuammmE coHuaHomoH :mH: mo unmemmcmuum Hmucsoo can uHHm .H musmHm £0.50th . :d _m .660 w - 2.10 at... m /[ 4. ..~oo.o I 3¢AUAHAV ufllll. “tum” ..¢oo.o I 203.035 20.50.! vaun— o.._.m<._w ...| azhmm KOPomhwo .muMHm mHnu so Umucsoo on on mmcoucH oou muo3 >mx Hmwm um wumum m on» m0 can >ox mme an mumum u on» no mpHmHm one .nmmumouuommm on» cH macaw mo mmGMHm mcouommwo o>mn moocwumMMHv owuma nocwx mo omsmown can moHuflusmEH Hm was m8 Roam umuumom SUan mcououm on pcommouuoo whens omoun was .zmzm .>wx OH usonm mo COHusHOmmH nqu .mmmumoc mm um A.m.mvmmme mo Esuuommm .N ousmHm mmmznz qwzcho 8m 9m 2: e a 1 4 .4 .flAiJId. ad. nu my .- e m a 1 V . 3 a 3 v Q 9.9 i0 0 8 .24.. m 0 n . h. .88 1 . N 3 3+ ow I. .2 . t h S I. .I is o 10 8% O 0 d . moo .w i a: my. a 3 o + 9 8 .I a 10 3 o 3 0 H w o i H 98 mm .m w -a A s \ 8 f >02 0&0 m 3 3 3 o "I «I 1m .414 . mu r. r. 8 .h . Ah avommn. .w m m m m i 8 h 3 .h 3 b b c b h‘ . b § 5 O OOOI .mumHm was» :0 counaoo on on wmnmucw oou mm3 >mx HHmH um oumum m may m0 meH5 was .Esuuommm mm on» :H mm .meuwunm IEH Hm can at Scum Hmuumom 50H£3 mcoumum on Ugommmuuoo mxmmm on» mo :Hmmmmo Hound mmsbn omoun one .zmzm .>mx 5 usonm mo GOHuaHommH nqu .mmmumop ov um A.m.mvam¢vH Scum Eauuoomm .m musmHm mmmzaz szzmzu com com oor com com o3 o 84 $8 mm fig 1 mm a .0 m m . a c. N .0. 8.8 e 8 w l T “a w m we. 8 w M S + m. h . R afl nu .0 .h... .f O 3 m. a H a 8 n 8 W JnU fiu meL 8. w 0 w .3 ow a 8 N .. >22 81$ .8 w .m 2L 3.3.53. w. w. c . Q h P P p p 0 0 85 m0>H50 0.2. cm" L .:L .J Era-C1112. ..- filiaiwln .. va can UGM MmmmH 3.3.5.6 om 9w Hz. om 8...— ddqddddddd‘dqdddd .2 .2 .2 .2 .2 cm— 382 .5 can 00 Am. .3. cm .A¢m .momv mmchmme cam Huumnooom «0 muouoamumm Hmwos HMOHumo ms» nu«3 move mGOHuMH50Hmo Hoooa Hmoaumo mo muHsmmu mum Cam qua—dqd—duq_jfi—dqq—uqq‘ lllLL l L ihlllll l l .2 .2 .2 .2 .2 .2 HOM consummfi mcoHuanHuume HMHsmcm mqflumuuwom UHHmMHm om (IS/aw) tsp/DP .v ouauwh 86 :- a I- "3 P h: o 3 10 .. .. 3’ Z . ,3 p d . '3 b d b- u: I 10' .. r : h d - 4 10-2 lJJllJllllllllLlLJlJlJl o 20 80 60 80 100 120 90m. (deg) Figure 5. Characteristic curves obtained by averaging 0&58 measurfid angular distributions from groups of states in Ba and Sm which had previously assigned J values. 87 3. - r- . -: 104: -: -3 .- .. -3 10-8 1 ‘7 F a 3 4 17 d y. 3 a p 1 g 10"1 .- 2 10", 3.339. 2 ~ -. '0 Z : t 1 L- 1 Z, l 3- 1 3‘ «4 3 4 . 3 10-8 2&339.22* 10-1 C I C I r- q r- ‘3 10-311111L11L141U4111LJA11 -2AlllLlllejlllllJIJJLLJ 0 20 ‘00 60 80 100 130 0 30 ‘30 60 80 100 120 Figure 6. States in 138Ba which have ngular distributions in agreement with the characteristic 2 shape, which is the line+drawn through the data. We assign all of these states J =2 with the exception of the state at 3050 keV. Lens,» 1 .‘ .x (A_'.‘“ s- "- “n“ ‘ ... J — .. g“ Figure 7. (niu80 davdn 144 States in 10° 1 VIVFUU' F 10° 1 T 'V'II' j 10'1 10'1 10'2 I I V'U'U' V 10'3 ...1.ii1...12..1...1... 88 1 d 1 1111111 1 1 1111111 1 1 411 1111 2010 etunfideg) in agreement with the characteristic 2 line+drawn through the data. J =2 . 8080 100 120 Sm which have ngular distributions shape, which is the We assign all of these states ‘15...- W..- moon-L‘s JAW 4. 89 1.1.." .... . .1. he 1‘ I 1.0.... ug‘la‘. 1 , . . mu b mmumuu mmmnu cmammm m3 .wump on» nmsounu 23026 ocHH as» aw cOan .mmmnm.|m owvmwumuomummo on» nuH3 usufimmumm 2H mcoHuanHuume umHamcc m>mn 50Hn3 EmevH can mmmmH 2H mmumum .m ouanm 332$ ‘ 3.3.5.6 own 8— am 8 or cm 9 Own 03 co 8 or cm 0 dqqdqqd—qqu—dqq—u-q—qdq 9b" dad—q-qqddqq..q—u+1—dqq TO" I L I L I l T P r. 1 V P m m m m p I 1 .2 .. 1 .2 b . . W 4 -m E3 3. 0 I 1 v ._ fl 1 1 1 ). a U H . w T l T 1 / h u n u N. n. a h n. u. I\ .2 .2 I . . . . . -m..mm.~ . . -m__m_ . . . m H 2 i Emil ammo 90 IF:.I:I- - .iwwwdr «u b mmumum ommnu mo HHm cmHmmm m3 .mumn on» gmsounu czmuc mcHH on» mH 50H£3 .ommcm v owumH Immuochmao on» zuH3 uswfimmnmm :H mcoHuanHHuch HMHsmcm m>mn SOan mm 2H mmumum .m ouamwm and .6. . . 3.3 us 3.2 e 8m cm” 8a DO 00 0... ON 0 .ON« cod 00 O“ or ON 0 «qdfilq—uqi—q44—«aq—‘q mIOH Jd—uqq—qqldqa—aqd—uq ”IOfi I 1 T n i n m u m ... 4.22 .. m...2 . Lu 69.” . . f 1 I p Au. AV 1 J D I L I 1 / I n v .. p m . + m m m u . ~-2 . . 72 ) a . iv mom N w I J I L q [I . . 3 3 m: I C j I L n U n u n ‘ . m. . .m - .8 .25 . 1 .2 . . 72 T A I 1 T A .. a . i W H n .v mmm. H 91 ".1 lialh runakmruv... .I llmg ¢u a banana onosu mo HHm cmflmmm m3 .mumc on» canons» czmup ocHH,ocu mH coas3 .mmmnm ¢ owuma Iuwuocuonu on» spas ucmsownmm 2H mcoHuanuumHv HMHsmcm m>ms coac3 quvH 2H mmpmum .OH shaman 3.25.. 3.25... cm" 8" cm 8 or cm 9 cm" 2: cm 8 2.. cm a 4.....*_.:_..._..._...NIOH §NIOH ,0 I L 1 111111 1 '11.! U V 72 'IIIII I 1“ J111114 L¢1 tsp/op 'UI'VTj VJ I 'o F. 11111 1 1 'u" C) C". (W) 1 V 1 1 V L Y Lu .mmm.m .v ._m_.N I'U‘T1 I 11111 1 1 'UfVTTT 11111 L 1 92 .am .HOHnsoc mswma mmOHo m on 582 manna mHnu .moncwomum3Hou as sumo as» no . o vmcmHmmm coma mm: 2m +mum mo>uso owumwuouomummw 0:» can .>0x omow an 00888 w 3.3.66 a. mumum >02 «mam 0:5 m can « 02» spam 0”“ .52.... 59—. 9m 00 .3. em a 4dJ1dJ—4qd—‘dd3-ddd-ddd om“ :. mun». >02 moan 8;» ou_ mu omHu+on n :mHumc 03 cu mac pan .20HuanauumHv AMHsmcm mHnu cmsoucu :3muv 2H uoHndoc a mo Honsme >82 Homw xmw3 cosmHMmm mHmsOH>on ommHuOH unawuanwuumHn .HH shaman omu .3: .xw am. .2. ow ._ add—.1d—«qqqqdddqdq_#qd Ib— n U I A H. h ab“. I i 1 1 I 1 h “a... I t I i I . 1 H . i u 382.com»: o 8:83 r. .8. I IIIIII I IIIII IV‘I I IIIT—II I I ¢ 1 1 111111 1 1111111 1 111111 1 1_¢ HMHnmsd ob" ob" n? n. mm U L: .l\ L: 93 .A5m .mmmv MHm>Huoomwmu >02 mevw can maem um mmumuw on» How umummoucm coon m>wn m can m mo mswmm .2203 was» 202w mama 0n UHnoo ucmesmammm :n 0: nng3 new on 2H moumum mm chHUfinHuumHu AMHsmcd .NH shaman 2H . . 303.88% 3ch E 0% o2 o2 8 8 2. 9.... o . 8. 8. 8 8 3. e. 8 o «..—.¢¢-4uddd+4d.dqdqdd TD“ dun—.qqdda._dq1—qqq—4qd ”1°“ 1 I I + H E... .. l 1.2 - . -~-2 0 . t. + . . 9.8m . W H o+++ . . . U H mmm.m + U n H m. WIS .: “:3 by ( kw o + 1 . + L . . . . . + . . .3 + . . H m . + m m 5.. + u w 2mm m hung v QWN 8.033 94 IE1...I.:I:.. -IHHEM! .HH .mmm 2H A159" 5 omcmwmmo soon as: >02 mmam um mucus one .2203 was» scum coma on uHsoo usoficmammm 2n oc+noH 3 you 2m 2H noun». mo nsowusnwuuch uanmsd .mH musmwh . . va . . 3.28.8 3.258 cm" .8" cm cm or am am I Om emu c3 on 8 o: . 0.0. o IOH . i . . . ... + + H H U I A + :m-2 : . . .. -2 wow... . + . a my . . . . . W m H H on on. H U m . . m m 8... .. l m ) ._.I II hulOH n: h IOH W . .4 . h I I .. I I 1 1 I I I .. I II J m 83 m n m n. h cod v mm..m . mane“ 9S j? a: :1 LL 3.33 3.35 3,36 3‘38 ’ 29 3.3.. 3.37 -,L¢__-{1—-, .31:._; 327 3.29 326 _--"-’———0 .5;__: 3.29 3.26 3,23 ‘ * j I a. 1 3.22 3.2“ #553; 3.23 3.22 3'25 .2:- _ 3 ,7 3.19 .320 3.19 h 3.1% . LLb—fi 3’16 3,32 3.13 _ ’ !l* 3,13 3.13 39 m :j—D: _“1_—* 3.05 3.06 3'08 3.05 - . 9.. .0:— 2 98 .a__+ 2.99 3-01 2.99 D. o - 3,92 2.93 - 2+ ~3— 233 3. 2.93 _:r+__ 2+ 7 5. 33° 2.29 - + g; 2083 - q‘ 2.83 2.85 [1* 2.78 Ho 29 2.6“ 25" L 2‘ 2,30 2.60 - 1+ 2+ 2.37 2.58 3’. “O. - 5+ ‘3:— 2953 a 51 2'“ ' 3+ - 15+ 1 L— 2 w Iii—h a go 2..“ 5+ 232 2.91 ' - 3+___ ' 2.35 2.37 M ‘19 2.31 El 2.3! 5+ 2 £ 2.20 b 2.99 L— u" 5’ 192 Mt b . w '“ 1.79 1’ 1.51 2 v A 1m ‘9‘“ 0* m m m m m 8813-905 INTEWTIM miss-mo INTENTION! WT 1388 1388 1388 R R H Figure 14. Comparison of results of shell model calculations discugged in Sec. IVA.with experimentally known energy levels in Ba. “mitt. ._‘_ . .-.‘_' 96 1‘09 ‘09 . 4L— 13.7 5° 3.3. 3' av’u” IL 3.13 3.20 3.“ 3.“ 3.12 b w -JL————-——-su1&“. i,. E! 'fll __ i, 22.37: w a '19 1' w w ; —‘?—— 2.“ no t.“ I _h———_. 1.“ ii it w w L—‘_ “ ~ .L .. -n n L— 373 w w m—_ m J- -“———————-un . LN h um -1L——————-Lu A—___ m .h—_—_ m It m kit!” WT!“ WT HHS" HHS" Figure 15. Comparison of.results of shell model calculations disguised in Sec. IVA with experimentally known energy levels in Sm. . 97 L . L . 10° __ L436. 2 * 1 10° __ 1 § 3 E |.898. 4* i D .. I h ‘ is 10-1: 1 10-1: 1 q . 4 L 4 Q ¢+ j A, J .8 101 : d7 10_1_ a... 2.090. 6+ -7 E 2.88I. 3- E i . J >- . 10° _. 1 10'3L . s s E a 10-1 WM 10-3 WW 0 20 "lo 60 80 100 130 0 20 ‘00 60 80 100 130 9cm(deg) 9c.m.(deg) Figure 16. Results oflggllective model calculations for in- elastic scattering on Ba The optical model parameters given in Table 2, Set SII were used, and both the real and im- aginary parts of the optical mode1+wer§ degormed. The calcu- lations shown are for the lowest 2 , 3 , 4 and 6 states. ’ ' ' T F |.66|. 2 * ‘ ’ ‘ . . Z . . t : t - : L .. . 210".- . 10":- -. i; E 0'5 E E v I 1 C I <3 ‘7 :7 v P d I- \ A, 4, ' - - 2. 24. * '3 101 .- 1 10 1.- +. 3 6 1 * - 1 E : : L84L13 . _ I. . u- d u- q r- d L- . -< 100 b 1 10-2 r 1 .. .. .- q C 1 Z 3. I I .4 P .. 10-1lllllLLlllLllllllLdlll 10-3 llLlLlllllelll'LlLL 0 20 90 80 80 100 120 0 80 90 60 80 100 120 9mm”) 9mm) Figure 17. Results oflggllective model calculations for in- elastic scattering on Sm. The optical model parameters given in Table 2, Set SI were used, and both the real and im- aginary parts of the optical model were degormed.+ The calcu- lations shown are for the lowest 2 , 3 , 4 and 6 states. W“"‘-"—"-r_' .4. 99 —Dm10m --- DIECT 1° . I:\ .7 \ . 10936. 2+ 1 1 b ‘ \ . ’ 0 16' - ‘x ( Jr v . 9 \ ,5 . 9 \ I . I 1.898. Q" 32 H? E:-' \\ '0 3 5 ‘ . \ __ .2 . . 10“ t1 ‘fiq— r l 10.; .— . 2.090. 6+ : ‘00 g 09 x ’ \ F " \° 0 \ 10‘ __ \ \ E \ : \ 10" 0 20 110 60 00100120 9cm(d”’ Figure 18. Microscopic model DEBA calculations foi3§he in- 10" 10“ 10" 10" 10" elastic scattering to the 2 , 41 and 6 calculations are identical except for left hand column employed the A=136-l40 set while the A=l36- 145 set was used for the right hand column. wave functions predict very similar angular distributions. l I r ‘1'" I 1 WTVUII' V I 'I'IU' b I'IIUIU'] T11 —— OIKCT o m -- - DIRECT ‘ 290909 6+ 0.. ... C. x I A \ 0 \ 0 \ ~ \ \ 0 20 ~10 so so 100 120 in 9mm) states in Ba. Both sets of The e wave functions; the dc/da (rub/5r) Figure 19. 10' 10" 10‘ 10" 10" 10' 10‘ 10" 10" 10“ 100 -—-qnmmro£xmnaz ---0mcr 2.218. 24- 2.308. 9+ 2.201. [6+] 20 40 60 80 100120 Hammeg) 10' 10" 10' 10" 10" 10" 10* 10" xcept for —- DIRECT 0 am - - '- OIKCT I I. 20218. 2* I 20308. 9* / 7" V I U""' T V IIIUV" I \ /\ 20 90 60 80 100 120 Microscopic mod 1 D cal ulations fo he in- elastic scattering to the 2?, 4gngnd BS f3§ calculations are identical 3 left hand column employed the A=l36~l40 set while the A=136- 145 set was used for the right hand column. indicate that the A=136-l40 set of wave functi states in Ba. ghe wave functions; the better description of the low lying states in Ba. These calculations gag provides the ._ ‘ 71‘ fifr—W‘T‘w " :.= ..| .< 101 M0,. —A'l36-|40 m _A'l36'|40 -—-A cuss-145 —--A=136-145 1'2 F LSJ'TM Figure 20.133ransition densities for the 2+ 2, 4+ and 6+ 2 states in+ Ba alculated with both sets of wave’gunctiohs. The 2 , 4 and 6 densities are very similar, and+predict vegy similér c}oss se tions. The differences in the 2 , 4 and 6 cross sections are directly related to the differenceg in thg transition densities for these states. ‘L:_o-gu-u.n an...- .‘J-_ 9 “AW . 102 114 . I; . n :3... {9.1.1 1041--...- . J i.“ In L” .umm mwa1mmau¢ on» sufi3 omumasoamo ma cesaoo poms semen 0:» means new oeauemane 0:» sues emumasoaeo we 0950mm came some one .meofiuoesm m>ez mo mama coon nufl3 omumaooamo .mmmma ca auwmcmo cowuflmcmuu +o may no cowuflmomeoo .HN musmflm E E b b qu cad .839 99m . 0Q; cad HI, .q a 1 .4 fil1 . q .. 46fi91 .. e8 1.2... 103 CENTRRL+TENSOR+LS — - — CENTRFIL ONLY 10"" _ 1 5 2.415, [5+]: : + ***+++ 1 10'3 '7 1 Q * “ 13 b e .5. ‘t \ 10.2 _ 2.4%, 3+ .2 c: : It :‘ Q : + + +++++ t) . U 1- - / \ I. b \ lifq 11111R11l111.1111111111111 0 80 ‘+0 60 80 100180 Gunfideg) Figure 22. Microscopic model DWBA calculations for inelastic scattering to the 3 and 5 states in Ba calculated with the A=136-140 set of wa$e functions. The two-body force included central,tensor and L15 terms, but no collective enhancement was included. Only the Direct + Exchange calculations are shown. .~ a: v” “3‘" ‘- 2’ 'JmnnLub‘ 104 -— DIRECT 0 5m -- - DIECT 10 ' —— once? 0 cm 10 ° . - - -' DIECT . . I 23*23. 2+ I .3 . 9 a l , r M...__._—__._'...e_m—_ sou-aw“ ‘ r _ _ . ..- . g . n da/dn (mb/sr) .. 2.32». (6+) 0 10“ 02090608010030 020‘106080100120 Figure 23. Microscopic model DWBA+calculations £25 inelastic scattering to the 21 , 41 and 6 states in Sm calculated with the A=136-145 ség of wgve funétgons. The inadequacy of the basis space is demo strated in+the calculated angular distributions for the 22, 42 and 62 states. APPENDIX C COMPILATION OF EXPERIMENTAL ANGULAR DISTRIBUTIONS 105 on+m:m.m n.m0a oo+mhho. nosmmoo. oo+mmm.m ¢.m0a noommm.m o.nofi oo+mo:o. no+umno. oo+mmm.a 3.00” Honm:m.m o.mm «o-umom. «onwamo. ao-mmm.m ¢.mm. o+mma.m 0.0m oo+ummo. 004mmdo. oo.mma.m ¢.om oo+m:s.m o.mm on+momm. oo.m«:o. oo+um¢.w ¢.mm Hn+mma.m o.nm ao+msmo. do.mono. Ho+umd.a 3.0m oo+mon.m o.mn ooomumm. oo+mmoo. oo+mno.m ¢.mn no.woa.m 0.0a oo.mm««. no.m¢mo. oo.m¢n.m ¢.ou nn+m¢s.m o.mo oo+umma. no+m¢mo. oo+mo¢.o ¢.mo Ho+mcm.m 0.00 do+uomo. ao+mmao. doamsm.m ¢.oo Ho+m¢m.m o.mm ao+mmmfl. «osmmmo. doomom.m :.mm ao+mcm.m 0.0m do+mmn«. do+mmflo. aoomdm.m m.om «oomom.m o.m: «commOa. Hoommmo. uo+mmm.m m.m: do+mmh.m m.m¢ so.msdd. so.mdmo. fio+wma.m m.m: Ho+mom.o 0.0: ao+mnma. ao+mmmo. ao+mma.o m.o: mo.m0a.~ o.mm mo+mmoo. mo.maso. mosmmo.m m.mm mo+mmm.e n.om moouosd. moommmo. mo+ums.: m.om mo+men.m o.mm mo+ummo. moommoo. mooumo.a N.mm mo+m::.m o.nm moomda”. mo+mm¢o. mo.mmm.m a.om :nouoa.w n.md :o+mo¢o. :o+m«mo. ¢o+m¢H.a «.ma .mm\mr. lawn. .«mxmr. Ammxmr. .amxmz. .omo. .m¢4.mr ooo. .xm .>mr o.om.nm zmnkumm mmoau unkm<4m .a.a.mmaur om:.fi .xm .>mr m.mm.am . 0m ..a.acmmamy mmm.a nxm .>mr m.mmnam .: ..a.a.mmd«m .hL.‘ .1121: 1 Noam:Mom Nonmwnom Nonmem.m 00.000.m mo-m:u.u mnemoaom NOIMuoom «Cowhnod 0.000. M0.00..m .mmxmrc .m.4..y0wm0 0.00 0.mo 0.00 0.00 0.0m 0.m¢ 0.0: 0.00 0.00 0.mm 0.0m “000. “004007. .>0r 000.0 .xm 00.0000. 00.0000. 00.0m00. 00.0000. 00.0000. 00.0000. 00.0000. donumwo. 00.0000. 00.0000. «Olwhuuo .«m\mr. .000 Jqpop .>mr m.mmuom 00.0000. 00.0000. 00.0000. 00.0000. 00.0000. 00.0000. 00.0000. “0.0000. 00.0000. «0.0m00. «0.0000. .mmxmr. .mmw.»<»m 00.0mm.0 00.000.0 00.000.m 00.000.m 00.000.0 00.000.0 00.000.0 00.000.“ 00.000.0 "0.00“." 00.000.“ Amm\mzv .ru04ruumo +0 0.00 0.00 0.00 0.00 0.00 0.00 0.0: 0.00 0.00 0.00 0.00 homo. “20.074 ..a~avmm«wr mam.m uxu 0>mr m0mmnaw .0 ..0.0.000(m mo.mso.m 0.00 NOIMMOo¢ 0.05 00.000.0 0.00 00.000.0 0.00 00.000.0 0.00 moommmom 00m: 00.000.0 0.00 00.000.0 0.00 doammmou 0.0m 00.000.0 0.00 00.000.0 0.00 .00x000 .000. 00000070000 0000.070 .>0y 000.0 .x0 00.0000. 00.0000. 00.0000. 00.0000. 00.0000. 00.0000. 00.0000. 00.0000. 00.0000. «OIM¢moo 00.0000. 00000:. .000 0(000 .>0r 0.00.00 00.0000. 00.0000. 00.0000. 00.0000. 00.0000. 00.0000. 00.0000. 00.0000. 00.0000. 00.0000. 00.0000. 00000r0 .«mm.0<0w 00.000.0 00.000.0 00.000.0 00.000.0 00.000.0 00.000.0 00.000.0 00.000.0 00.000.0 00.000.0 00.000.0 Aam\mzv 0ru0ur md:.m .xu .>mr m.mm.au .+mv ..a~a.mm«ur m¢:.m .xu .>mr w.mm.am . ém :m~mvmm~wr :mm.m .xu .>mr m.mm.am +¢ ..a.¢.mmfl(m mo.mm..s 0.00 mo.momm. mo.mwhh. mo.mm..n ..oo mo.uad.~ o.mm mo.uuflm. mo.mdmo. mo.mmo.n $.mm mo.m:fl.d 0.0m mo.mmafi. mo.momo. mo.mm".fi m.om modmm.H o.m: mo.moma. mo.mmnfi. mo.mmm.a m.m: made...‘6 0.0. mo.mmmfl. mo.uomo. mo.umm.d m.o: mo.mna.~ o.mm mo.momm. mo.mm¢m. mo.mafi.m m.mm mo.mmm.¢ o.nm mo.momm. mo.mmmm. mo.uu:.¢ m.om mo.u¢m.m o.mm mo.mm¢¢. mo.unma. mo.uon.m m.mm moummn.4 0.0m mo.uo¢m. moumanm. mo.»~o.: m.om .am\mz~ .omn. .wmxmy. .mmxmr. .mmxmz. homo. .m(4.(rm_mo .mur mmo.m .xu .>mr m.mm.am 0N ..o~uvwm«mr mnn.m .nxu .>mr m.mmwa_m +¢ ..a.avwma0r 000.0 .x0 .>0r 0.00.00 .m 0.0.avwm00r 000.0 .x0 .>0r 0.00.00 0.0 0.0.0.00000 mo.umm.m 0.0» mo.m:nm. mo.mmmm. mo.m:m.m ¢.on mo.wmfi.: 0.00 mo.m:om. moommdz. mo.m:fl.¢ ¢.oo mo.mdn.¢ o.mm mo.mm¢m. mo.mo~:. mo.mum.m :.mm mo.mma.m o.om mo.mmmm. mo.ummm. mo.mmo.e m.om mo.mm..m o.m¢ mo.mmmo. mo.mmmm. mo.mmm.m m.m¢ mo.mmm.fl o.o¢ mo.ummn. mo.wmmo. mo.mflm.fi m.o: mo.mm:.d o.mm mo.mmmfl. mo.mono. mo.us¢.fi m.mm mo.mm,.fl 0.0m mo.mmed. mo.manfi. mo.mfi:.fl m.om mo.mmm.m o.mm mo.uomd. mo.mm¢fl. mo.mmm.a m.mm .mmxmr. .omn. .mmxmyv .mmxmr. .mmxmz. Ammo. .m<4.«rmmmn .m(4vm7« .mam J<»o» .mam.»¢»m .xuvwr emd.m .xm .>mr m.mm.am +¢ ..a.avmmdmr :mm.m .xw .>wr m.mm.mu yzozyza ..a.¢vmm«my mmm.m .xu .>mx m.mm.am ywozyza A.a.m.wmfi0y 000.0 .x0 .>0r 0.00.00 om ..a~a.mm«0y 000.0 .x0 .000 0.00.00 0m ..a.a.wmamr 00m.m 0x0 .>mx w.mmnau 0+0. 0.000.0m040 85mm.H o.m«« oo.mdoo. oo+modo. oo+uoo.m $.maa oo+uom.m 0.0“" oo.ummo. oo+mhfio. oo+wam.m ¢.oda oo+mmm.m o.m0a oo+mmwo. oo+m¢mo. ooomom.m ¢.mo« oo.u¢~.d 0.00” oo+u¢mo. oo*umao. oo+m¢n.fi 3.00“ oo+mum.m o.mm oo+um:n. oo.mfido. oo+umm.fi :.mm oo+mmm.m 0.0m oo+umfifi. oo+mmmo. oo+mmm.m ¢.om oo+m:n.m o.mm oo.mmm~. oo.umdd. oo.umu.m ¢.mw Ho+mm~.d o.ow do+mdso. do+m¢do. fio.mmm.fi ¢.ow Ho¢uun.m o.mu do+mmmo. do+m¢«o. “oouno.a ¢.mn oo.mmm.¢ o.on oo.ummfl. oo.mo¢o. oo.uom.¢ :.on oo¢mwm.m m.no oo+um««. ooow¢mo. ooomom.m m.no oo+mmm.n o.mo oo+u¢mm. oo+mmmo. oo+mom.u ¢.mo d04mo:.m 0.0o “o.mhofi. do+m¢mo. do+mmm.m :.oo «0+mm:.m o.mm flo+umom. do+u¢oo. Ho+mm:.o m.mm ao+m:a.u 0.0m ao+momm. ao+m~mo. ao+mno.n m.om fio+mwn.o m.u: «n+mdmfi. «oomdoo. ao+mmo.o m.~¢ flo+umm.m o.m¢ do.w:oa. Ho+ufimo. do.mom.m m.m: Ho+mmn.m m.m: do.mfiod. do.momo. doomm0.m m.m¢ ao+mmu.n 0.0: «commam. «oommso. «o+umo.u m.o¢ moommm.m o.mm mo+ummo. mo¢uwmo. mo.moo.m m.mm mo+mm:.c 0.0m mo.u:om. mo.mumo. mo+m~a.c m.om mo+unm.m o.mm mo.mm¢o. mo.wmao. mo+umm.« «.mm mo.um:.: 0.0m mo+mmmfl. moommuo. mo+uum.¢ «.om :oomwm.m o.m« sooummo. so‘mmmo. ¢o+wom.a ”.md .mmxmy. .cun. .«mxmr. .mmxmr. .mmxmz. homo.- .m44.wy ooo. .xm .>mr o.om.¢u zoubumm mwoau U~Fm<4m .m~m.¢:drm mo.m5d.o 0.0«H mo.mom¢. mo.umom. mo.mom.o ¢.o“a mo.mm¢.m o.m0a mo.mm:¢. mo.mmom. mo.u~c.m ¢.m0a mo.mm¢.~ 0.00“ mo.umum. mo.ummm. mo.mm¢.n ¢.00a dogm¢n.fi o.mm «oounno. «ouummo. floou¢o.fi ¢.mm do.ufim.d 0.0m do.mumo. ao.mmmo. Ho.mdm.fl .¢.om “o.mmfi.d o.mm “o.u~mo. do.wmmo. do.umfi.fi ¢.mm Ho.mmfi.d 0.00 «o.ummo. do.mmmo. Ho.mwd.fi ¢.om do.mom.fl o.mh do.uomd. ”o.m:MO. do.uow.d ¢.mu Ho.mmm.m 0.05 «o.mmmfi. do.momo. fio.moo.m ¢.ou «o.mwm.m 0.50 “o.mddm. do.umoo. Ho.mnw.m ¢.no Ho.mfim.m o.mo do.mmm«. do.momo. Ho.umm.w ¢.mo do.m«n.m o.sm Ho.mm~m. do.wmmo. «o.mmo.m $.um «o.mmm.o m.u¢ do.ufib¢. do.mmma. "o.u~¢.e m.u¢ do.mm:.s o.m¢ «o.mmmm. «o.ummo. “o.mmm.u m.m: fio.uma.o 0.0: do.u¢o¢. do.mmud. do.uma.o m.o¢ do.mm~.o m.um do.mum¢. do.mnmfi. do.mfih.o w.nm Ho.mdm.m o.mm do.mmoo. do.uwmo. ”o.mom.m m.mm 8J3.H 0.0m oo.mnma. oo.m~fio. oo+uom.d m.om oo+uflm.m o.mm oo+m~o~. oo+uo:o. oo+mwm.m m.mm oo.umm.m 0.0m oo.umhfi. oo.mamo. oo.wwa.m fi.om oo+ums.M m.ofi oooummfi. oo+mooo. oo.uon.fi 0.0“ oo.mmm.m o.mfi oo+waofi. oo+um¢o. oo+mom.fi «.NH .mmxmr. .omn. .mmxmr. .«mxmrv .amxmz. ammo. .m(4vwr "no.“ .xm .>mx m.mm.am +~ ~.a~a.::arm Ho.mmm.m 0.0a“ Ho.umoa. Ho.mmmo. Ho.mow.m ¢.od« do.m¢fi.m o.moH Ho.mmmm. ao.wm¢o. Ho.uma.m 4.mo« d0&2... 0.00“ do.mmm~. Ho.mmmo. Ho.mofi.: w.oo~ Ho.mmm.4 o.mm "o.umam. «o.m¢mo. Ho.mmw.¢ :.mm “o.mas.: 0.0m «o.ummm. do.mmoo. do.u¢s.¢ ¢.om do.m¢m.¢ o.mm "o.m~¢m. do.mamo. Ho.m¢m.¢ ¢.mm «ovmwm.m 0.0w «ouuam:. «onmmmo. donmom.m euom do.mmm.m o.mu «o.ummm. do.umuo. Ho.mmm.w ¢.mh oo.mmd.a 0.05 oo+ummo. oo*unoo. 00+Uhfl.d ¢.on oo+mmm.a 0.50 oo+mmmo. oo+umdo. oo+w:m.d :.no oo.mmm.d 0.5m ooommOa. oo.mwdo. oo+mmm.d ¢.nm oo.mo¢.fl o.om oo+ummo. oo+umflo. oo+mmm.d m.om oo+mmm.m m.h: 004mmaa. no+u«mo. 00§mum.a m.u¢ oo‘mmn.m o.m: oo.um:d. oo.wmdo. oo+mmo.m m.m¢ oo+mns.m 0.0: oo+mm:m. oo+un¢o. oo+um¢.m m.o: oo+uom.¢ m.~m oo+u:dm. oo+uumo. oo+mm¢.¢ m.hm oo+mfid.m o.mm oo+wmmm. no+u~mo. oo+mmo.m m.mm oo+mmm.: 0.0m oo+mm¢m. no+udmo. oo+mow.: m.om oo+m¢o.m o.mm oo+unmm. oo.ummo. oo+mmm.m «.mm oo.mom.d 0.0m oo.mmoa. oo+modo. oo.wmm.d H.0m «o.mmm.~ m.sd Ho.uamo. ”o.mmom. “o.mmn.h $.Ba oo.umn.m m.od oo+u¢wo. oo+um¢o. oo+mmo.fl 0.0“ do.umm.o o.m~ Ho.u~n¢. "o.mnmfl. Ho.mom.o “.md .mmxmz. .oun. .mmxmr. .mmxmr. .mmxmz. ammo. .m<4.wy “an.“ .xu .>mr m.mm.mm um ..m~a.¢¢arm mo.umm.m 0 o.mm mo.uwmm. mo.mo~m. mo.umm.m ¢.mm mo.mm:.m o.mm mo.mma¢. mo.msod. mo.mm:.m wqmm mo.mom.u 0.0m mo.u~mm. mo.m¢oo. mo.m¢m.h ¢.ow mouudm.m o.mu mo.mmon. mo.mmom. mo.mwm.m e.mn do.mma.d o.mo Ho.mmmo. Ho.mmmo. “o.um".d ¢.mo Ho.mom.fl o.mm «o.umofi. do.mo:o. do.mmm.a m.mm “o.m:n.m 0.0m ”o.uoma. «o.unoo. Ho.mmo.m m.om ”o.u¢o.m o.m¢ “0.“:Hm. do.mumo. do.udo.m m.m¢ Ho.uo¢.m 0.0: «o.mumm. “o.m~mm. Ho.mm¢.m m.o¢ do.Mam.m o.mm «o.umhm. «o.wmmo. do.mow.m m.mm «o.mm~.m 0.0m «o.uunm. flo.mmmo. Ho.mos.m m.om “o.mmd.¢ o.mm Ho.u~«m. “o.mmmd. do.w0a.¢ «.mm do.mmn.¢ 0.0m «o.uamm. «o.ummo. «o.mmm.m H.0m do.mum.: m.hfi Ho.mdom. «o.mmmd. do.uom.. o.sa Ho.m:m.o o.m« «o.um:.. «o.u00a. do.mmm.o ".mfl .mm\my. .omn. .mmxmr. Ammxmr. .mmxmz. memo. 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