Singles Spectra Research Articles

The 114In level scheme studied by the (n, γ) reaction

The level scheme of the nucleus 114In has been studied using capture of thermal neutrons. The experimental information is taken from γ singles spectra and γ- γ coincidence spectra and from delayed coincidence measurements. Levels up to 1.4 MeV excitation energy are proposed. Several short lifetimes of excited states in 114In and 116In could be measured. The binding energy of the last neutron in 114In, B n = 7273.9 ± 1.2 keV, determined in this work is in strong disagreement with previously accepted values. Additional experimental information on the 116In level scheme is given. Six states of the ( π( g 9 2 ) −1, ν h 11 2 ) multiplet (3 − to 8 −) in 114In. The expected close similarity between many low-lying states in 114In and 116In could be confirmed. In particular, it was found that the anomalous high isomeric cross-section ratio of the second isomeric state results from very selective reorientation transitions within the negative-parity multiplet. The coupling constant of the quadrupole part of the residual neutron-proton interaction obtained from a theoretical calculation of the 114In level scheme is similar in size to that of 116In, thus giving credit to the explanation given in our previous 116In work. The splitting of multiplets in doubly odd In nuclei gives additional information for an interpretation of the so-called g 7 2 − h 11 2 anomaly in stripping studies near A = 110. Transition probability ratios B(M1)/ B(E2) and E1 hindrance factors are discussed for both 114In and 116In. No sign of states exhibiting stable deformation similar to those in odd- A In nuclei has been found up to now in the doubly odd In nuclei studied. There is some evidence that these doubly odd In nuclei behave more like Cd than like single closed shell Sn nuclei.

Thermal and photo‐induced phenomena in γ‐irradiated poly(methyl methacrylate)

AbstractESR spectra and optical absorption spectra of γ‐irradiated poly(methyl methacrylate) (PMMA) at 77°K and the photo‐ and thermal bleaching behavior have been studied. γ‐Irradiation of PMMA yields a singles spectrum with a line width of 6 G which is bleachable with visible light. This species is assigned to the polymer cation. The unbleached species consists mainly of a four‐line spectrum and is assigned to a polymer radical having a different CH2 conformation from the usual nine‐line spectrum. On subsequent warming to room temperature, the spectrum changes into the nine‐line spectrum. γ‐Irradiation of PMMA containing biphenyl as an additive at 77°K gives biphenyl cation. Yield of polymer radical is reduced by the addition of biphenyl and 2‐methyltetrahydrofuran. A mechanism is proposed which is consistent with the experimental results.

Three-Body Breakup ReactionCa40(O16, C12α)

We report for the first time coincident $^{12}\mathrm{C}$ and $\ensuremath{\alpha}$ particles emitted in the bombardment of $^{40}\mathrm{Ca}$ with $^{16}\mathrm{O}$ ions of 64 MeV. Events which populate the ground and first excited states of $^{12}\mathrm{C}$ and $^{40}\mathrm{Ca}$ are observed. The coincident $^{12}\mathrm{C}$ energy spectra are dominated by one or two large peaks near the highest allowable $^{12}\mathrm{C}$ energy. Relatively few coincidences are seen at $^{12}\mathrm{C}$ energies which correspond to maximum yield in the $^{40}\mathrm{Ca}$($^{16}\mathrm{O}$, $^{12}\mathrm{C}$) singles spectrum.

Proton states, anomalous conversion, andK-Auger spectra inAm241fromCm241(electron capture) andBk245αdecays

$\ensuremath{\gamma}$ and conversion-electron spectra of mass-separated $^{241}\mathrm{Cm}$ (32.8 day) samples were measured at high resolution with Ge(Li) detectors and a magnetic $\ensuremath{\beta}$-ray spectrometer; 28 $\ensuremath{\gamma}$ rays and 76 conversion lines were identified. The multipolarities of most of the 28 transitions in $^{241}\mathrm{Am}$ were deduced. Two-parameter $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidences confirmed a level scheme incorporating all transitions in six rotational bands. The observed half-life of $^{241}\mathrm{Cm}$ via the decay of the 471.8 keV $\ensuremath{\gamma}$ ray was 32.8 \ifmmode\pm\else\textpm\fi{} 0.2 day. The $\ensuremath{\alpha}$ branching deduced from the measurements of ${L}_{2}$ and ${L}_{3}$ electron lines of the 145.5 keV transition in $^{237}\mathrm{Pu}$ was (1.0 \ifmmode\pm\else\textpm\fi{} 0.1)%. The $\ensuremath{\alpha}$ singles spectrum of $^{245}\mathrm{Bk}$ (5 day) decay to $^{241}\mathrm{Am}$ showed 12 $\ensuremath{\alpha}$ groups feeding the 3 lowest bands. On the basis of these measurements six single-particle states in $^{241}\mathrm{Am}$ have been identified. The ground state of $^{241}\mathrm{Am}$ is known to be $\frac{5}{2}\ensuremath{-}[523]$. The following Nilsson band-head assignments have been made: (keV, $K\ensuremath{\pi}[N{n}_{z}\ensuremath{\Lambda}]$: 205.9, $\frac{5}{2}+[642]$; $\frac{3}{2}\ensuremath{-}[521]$; $623.1,\frac{1}{2}+[400]$; 652.1, $\frac{1}{2}\ensuremath{-}[530]$; and 670.2, $\frac{3}{2}+[651]$. The 266.0 keV $E1$ transition $\frac{3}{2}\ensuremath{-}[521]\ensuremath{\rightarrow}\frac{5}{2}+[642]$) was found to have the most highly anomalous conversion coefficients yet observed, with anomaly factors of 100-200, consistent with $E1$ penetration conversion parameter sets ${\ensuremath{\lambda}}_{1},{\ensuremath{\lambda}}_{2}$ = (18.5,283) or (-19.3, -63); the exiting 205.9 keV $E1$ transition ($\frac{5}{2}+[642]\ensuremath{\rightarrow}\frac{5}{2}\ensuremath{-}[523]$) shows normal $E1$ conversion. The 471.8 keV $M1+\ensuremath{\sim}7% E2$ transition $\frac{3}{2}\ensuremath{-}[521]\ensuremath{\rightarrow}\frac{5}{2}\ensuremath{-}[523]$ also shows anomalous (factor of 3) conversion, with an $M1$ penetration parameter \ensuremath{\sim}5.5. There is some indication of anomalously low $K$ conversion for transitions near $K$ threshold. Observed ${P}_{1}$ conversion line intensities are about twice the theoretical ${P}_{1}$ conversion coefficient predictions. Seven $\mathrm{KLL}$- and two $\mathrm{KLM}$ - Auger electron lines were observed and the $K$-shell fluorescent yield was deduced as (96.5 \ifmmode\pm\else\textpm\fi{} 0.4)%.RADIOACTIVITY $^{241}\mathrm{Cm}$ [from $^{239}\mathrm{Pu}(\ensuremath{\alpha},2n)$]; measured ${T}_{\frac{1}{2}}$, ${E}_{\ensuremath{\gamma}}$, ${I}_{\ensuremath{\gamma}}$, ${X}_{K}$, ${\ensuremath{\omega}}_{K}$, ${E}_{\mathrm{ce}}$, ${I}_{\mathrm{ce}}$, ${e}_{\mathrm{AKLL}}$, anomalous $E1$ and $M1$ conversions, deduced penetration parameters and retardation, deduced ${\ensuremath{\alpha}}_{{P}_{1}}$, $\ensuremath{\gamma}\ensuremath{\gamma}$-coin, $\ensuremath{\alpha}$ branching, $^{245}\mathrm{Bk}$ [from $^{244}\mathrm{Cm}(\ensuremath{\alpha},p2n)$; measured ${E}_{\ensuremath{\alpha}}$, ${I}_{\ensuremath{\alpha}}$; deduced hindrance factors. $^{241}\mathrm{Am}$ deduced levels, $log\mathrm{ft}$ (EC), $\ensuremath{\gamma}$ multipolarity, $I$, $\ensuremath{\pi}$, 6 single-particle states. Mass-separated $^{241}\mathrm{Cm}$. Toroidal $\ensuremath{\beta}$ spectrometer at 0.05% FWHM.

Charge-exchange reactions on 91Zr

The 91Zr(τ, t) 91Nb(IAS) reaction and subsequent proton decay were studied at 24.5 MeV bombarding energy. Singles and coincidence decay proton spectra were measured, giving yields in agreement with the yield computed from the triton angular distribution. The singles (τ, tp̃) proton spectrum from 24.5 MeV helion bombardment is compared to the singles (p, np̃) proton spectrum from a 27 MeV proton bombardment. These spectra contain significant structure in the distribution of “background” protons (usually assumed structureless).

Levels in 45Sc from Radiative Proton Capture in 44Ca

A total of 22 resonances has been observed in the 44Ca(p,γ)45Sc reaction within the incident proton energy range of 600 to 930 keV. Gamma-ray singles spectra and γ-ray angular distribution data were accumulated for resonances at Ep = 856 and 906 keV. Both of these resonant states have been found to have spin 3/2. The measured angular distributions of primary γ rays from the resonant states have given spin information on the intermediate bound states of 45Sc with excitation energies above 2 MeV. A γ-ray decay scheme has been derived from the γ-ray spectra. The data indicate new levels at 2151.0, 3525.2, 3548.5, 3584.0, and 3714.3 keV.

Levels ofRb91andSr91fed in the decays ofKr91andRb91

Level schemes for $^{91}\mathrm{Rb}$ and $^{91}\mathrm{Sr}$ are proposed based on the study of the $\ensuremath{\beta}$ decay of $^{91}\mathrm{Kr}$ and $^{91}\mathrm{Rb}$, respectively. The samples were obtained using on-line mass-separation techniques applied to $^{235}\mathrm{U}$ fission products. $\ensuremath{\gamma}$-, $\ensuremath{\beta}$-, and x-ray singles spectra, as well as ($\ensuremath{\gamma},\ensuremath{\gamma}$) and ($\ensuremath{\beta},\ensuremath{\gamma}$) coincidence spectra, were taken with Ge(Li) and Si(Li) detectors. Internal-conversion coefficients were determined for several transitions and the half-lives for the first two levels in $^{91}\mathrm{Rb}$ and $^{91}\mathrm{Sr}$ were measured. In view of the observed parity change between low-lying excited states and the ground state in $^{91}\mathrm{Rb}$ the possibility of deformations to explain this level structure is discussed.

Spins of levels in 70Ga

The level structure of the nucleus 70Ga has been studied by means of the 70Zn(p, nγ) 70Ga reaction ( Q = − 1.435 MeV). Levels in 70Ga up to 1633 keV in excitation were selectively populated by varying the proton bombarding energy in the range of 1.7 to 3.2 MeV. The γ-rays associated with these levels were identified in singles spectra from their energies and their threshold behaviour. Gamma-ray branching ratios were obtained and a decay scheme for 70Ga comprising 58 transitions is presented. Angular distributions of de-exciting γ-rays have been measured at proton bombarding energies close to threshold for the levels studied. Comparison of these distributions with the theoretical predictions of the compound nucleus statistical model has led to spin and parity assignments for the levels studied.

Structure, Directional-Correlation, and Doppler-Shift Lifetime Measurements inCu61viaNi58(He4,pγ)Reaction Spectrometry

The level structure and the decay properties of the levels in $^{61}\mathrm{Cu}$ up to 4082 keV of excitation have been carefully investigated via prompt $\ensuremath{\gamma}\ensuremath{\gamma}$ and $p\ensuremath{\gamma}$ coincidence experiments employing Ge(Li) $\ensuremath{\gamma}$-ray detectors and annular Si surface-barrier charged-particle detectors. From these experiments and from high-resolution singles energy and directional- correlation measurements an improved decay scheme has been obtained which includes 44 levels in $^{61}\mathrm{Cu}$ and incorporates 120 $\ensuremath{\gamma}$ rays. New levels at 2584.5, 3739.4, 3942.4, and 4081.8 keV were postulated, while the $\ensuremath{\gamma}$ decay of several previously reported levels between 3277-3802 keV was not observed. The singles directional correlations from many transitions were used to obtain (i) reliable branching ratios for the more intense $\ensuremath{\gamma}$ rays and (ii) multipole mixing ratios $\ensuremath{\delta}(\frac{E2}{M1})$ by employing both a ratio method and an independent analysis of the correlations via the compound statistical theory of nuclear reactions. Branching ratios for the weaker $\ensuremath{\gamma}$ rays were obtained from spectra taken at 55\ifmmode^\circ\else\textdegree\fi{} to the beam direction. The lifetimes of 31 levels in $^{61}\mathrm{Cu}$ were measured by the Doppler-shift attenuation method via the $^{58}\mathrm{Ni}(^{4}\mathrm{He},p\ensuremath{\gamma})$ reaction at bombardment energies between 9.7 and 12.2 MeV. Lifetimes were extracted from singles spectra obtained at 0, 15, 30, 45, 70, 90, and 110\ifmmode^\circ\else\textdegree\fi{} and from $p\ensuremath{\gamma}$ coincidence spectra obtained at 0\ifmmode^\circ\else\textdegree\fi{} to the beam direction, by employing both a centroid shift analysis for the data from all angles and a line-shape fitting analysis for the data from angles \ensuremath{\le}45\ifmmode^\circ\else\textdegree\fi{}. The stopping power of Ni previously calibrated for Cu ions, was used for the line-shape analysis and for obtaining reliable $F(\ensuremath{\tau})$ curves applicable to the present conditions of both the singles and the coincidence experiments. For a large number of transitions in $^{61}\mathrm{Cu}$ values for $B(E2)$ and $B(M1)$ were obtained. The $B(E2)$ and $B(M1)$ values together with the $\ensuremath{\delta}(\frac{E2}{M1})$ values and the branching ratios from the first 10 levels in $^{61}\mathrm{Cu}$ are compared with recent detailed calculations for $^{61}\mathrm{Cu}$ based on a unified model. Good general agreement is observed between experiment and theory for the $B(E2)$ values. Only moderate agreement between experiment and theory is observed for the $B(M1)$ and $\ensuremath{\delta}(\frac{E2}{M1})$ values.

The 6 − analog-antianalog states of 28Si

A resonance is observed in the 27Al(p, γ) 28Si reaction at E p=2876±2 keV, which corresponds to an excitation energy of 14356±2 keV. The 14.36 MeV level decays to a new level at 11577±2 keV, which is turn decays to the known level at 9701.8±0.5 keV. With previous information on the 9.70 MeV level and the present γ-ray angular distributions, obtained from singles spectra as recorded by a 40 cm 3 Ge(Li) detector, the spins of the three levels can be limited to J=5, 6; J=6; and J=5, respectively. Transition strength arguments based on measurements of the strength of the 2876 keV resonance and the lifetime of the 11.58 MeV level indicate that the 14.36 MeV level has J π =6 −, T=1 and that the 11.58 MeV level has J π =6 −, T=0.

Line shapes of doppler shifted γ-rays from coincidence and singles spectra in measurements of nuclear lifetimes

Abstract A procedure is described for extracting nuclear lifetimes from the analysis of line shapes of γ-rays from either coincidence or singles spectra obtained from Doppler-shift attenuation experiments. The nuclear and electronic stopping powers in a given slowing down medium are independently adjusted to give the line shape and lifetimes of “standard” Doppler-shifted γ-rays, the lifetimes of which have been determined by other independent methods. The stopping power thus calibrated is then used to determine the lifetimes of other transitions from Doppler-shift attenuation experiments in the same stopping medium. Line shapes are obtained by including the effects (a) of the recoils that escape the target, (b) of the decay of other levels into the state in question, (c) of the γ-or particle-detection angles and their corresponding solid angles, (d) of the integration over the distribution of recoils in the singles experiments including angular correlation effects to a good approximation for angles of observation ≤30° to the beam direction, and (e) of the detector response assumed to be gaussian. Lifetimes are obtained from comparison with experiment using both a line shape fitting technique and the F ( τ ) or centroid-shift technique.

Transitions, with change in parity, produced in 107,109Ag by coulomb excitation

Some of the low-lying energy levels of 107Ag and 109Ag were excited by Coulomb excitation using α-particles from 4.8 to 7.2 MeV. Transitions to the isomeric state ( 7 2 + ), involving a parity change, were observed both directly in the singles spectra and indirectly by the decay of the isomer. The isomer in both silver isotopes was populated by transitions from the 5 2 − level, which was strongly excited. The observed branching ratio in 109Ag for the 5 2 − → 7 2 + transition was (0.315 ± 0.09) % and for the 5 2 − → 9 2 + transition was (0.055±0.03) %. The total rate of populating the 7 2 + level from the 5 2 − level was (0.215±0.04) % in 107Ag. The level schemes have been discussed on the weak-coupling model, allowing admixtures of singleparticle wave functions to account for the weaker transitions.

L-subshell fluorescence and coster-kronig yields atZ=92 and the decay of235Np

TheK andL x-rays emitted in the decay of235Np have been studied with high resolution Ge(HP) and Si(Li) detectors in coincidence, in order to obtain theL2 andL3 subshell fluorescence and Coster-Kronig yields atZ=92. The results are:v2=0.630±0.036, ω2=0.560±0.033,f23=0.147±0.010, and ω3=0.481±0.029. Results for theL1 subshell were derived from singles spectra, by assuming a value off13 of 0.67, and are:v1=0.54±0.04, ω1=0.21±0.04, andf12<0.07. With the same assumption, theL1/K electron capture ratio and decay energyQ ec for235Np were found to be 29.0±3.6 and 123.6±0.7 keV, respectively. RelativeL x-ray intensities forZ=92 also were measured and are compared with the theory of Scofield and with recent diffraction experiments. Electron ejection from theL shell during235Np decay has been studied byL x-ray-L x-ray coincidences and found to occur with a probability of (1.3±1.0) × 10−4 per disintegration.

Properties of Levels inPb198andPb200

The decay of $^{198}\mathrm{Bi}$ and $^{200}\mathrm{Bi}$ to levels in the corresponding Pb daughters have been investigated using sources which were both mass-separated and chemically processed. $\ensuremath{\gamma}$-ray and conversion-electron singles spectra were obtained, as well as $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ prompt- and delayed-co-incidence spectra. These data yield levels in $^{198}\mathrm{Pb}$ at the following energies (spin-parities): 1062.9 (${2}^{+}$), 1624.9 (${4}^{+}$), 1822.3 [${(5)}^{\ensuremath{-}}$], and 2139.8 [${(7)}^{\ensuremath{-}}$] keV. Those in $^{200}\mathrm{Pb}$ are at 1026.3 (${2}^{+}$), 1488.3 (${4}^{+}$), 1907.9 [${(5)}^{\ensuremath{-}}$], and 2152.9 [${(7)}^{\ensuremath{-}}$) keV. The half-life of the 1822-keV level in $^{198}\mathrm{Pb}$ was determined to be 63.3 \ifmmode\pm\else\textpm\fi{} 2.5 nsec, and those of the 1908- and 2153-keV levels in $^{200}\mathrm{Pb}$ are 1.50 \ifmmode\pm\else\textpm\fi{} 0.08 and 47.6\ifmmode\pm\else\textpm\fi{} 2.5 nsec, respectively.

Gamma-Ray Spectra and Level Structure ofCa44from Thermal-Neutron Capture inCa43

$\ensuremath{\gamma}$-ray measurements have been made of the $^{43}\mathrm{Ca}(n,\ensuremath{\gamma})^{44}\mathrm{Ca}$ reaction at the Livermore pool-type reactor. Singles spectra were taken with Ge(Li)-NaI(Tl) Compton-suppression and pair-coincidence spectrometers. A total of 280 observed $\ensuremath{\gamma}$ rays were attributed to capture in $^{43}\mathrm{Ca}$. Ge(Li)-Ge(Li) coincidence measurements using a three-parameter analyzer system (${E}_{1},{E}_{2},\ensuremath{\Delta}T$) were analyzed, resulting in the assignment of 129 of the observed transitions to 45 inferred levels in $^{44}\mathrm{Ca}$. Comparison of $l=1 (d,p)$ strengths $(2J+1){S}_{n}$ with ($n,\ensuremath{\gamma}$) strengths $\frac{I}{{E}^{3}}$ leading to the same final states yields a positive correlation coefficient of 0.63. The neutron binding energy is determined to be 11 131.6 \ifmmode\pm\else\textpm\fi{} 0.7 keV.

Isospin and decay modes of 6Li states from 7Li(τ, α) 6Li and 7Li(τ, α) 6Li∗ (d) 4He reactions at Eτ = 1.5 MeV

The 7Li (τ, α) 6Li and 7Li(τ, α) 6Li∗(d) 4He reactions have been used to study the energy levels of 6Li. Singles spectra provide evidence for five states below 6 MeV of excitation energy. These include the ground state and four excited states at 2.18, 3.56, 4.57 and 5.36 MeV. One- and two-parameter coincidence data confirm the identification of these levels and aid in the determination of decay modes and isospin assignments. The deduced isospin assignments for the five levels are T = 0, 0, 1, 0 and 1 with a small T = 0 impurity, respectively.

Investigation of T = 0 excited states of 4He via the 4He(d, d' t) 1H AND 4He(d, d' d) 2H reactions

The three-particle reactions 4He(d, d' t) 1H and 4He(d, d' d) 2H were investigated at an incident energy of 52 MeV. The energy spectra of tritons and deuterons were measured simultaneously with inelastically scattered deuterons with two detectors, one at a fixed angle of 31° lab and the other at varied angles ranging from 20° to 38° lab. The data are interpreted in terms of six resonances arising in final-state interaction through T = 0 excited states of 4He. Only the lower three resonances are prominent in the data. The extracted resonance parameters (energies and widths) are consistent with those obtained from measurements of similar reactions in two other different entrance channels. A summary of results from the present measurement and the two others is presented and compared with results from the phase-shift analysis. Singles spectra from the 4He(d, d') 4He∗ reaction were also obtained and used in addition to the coincidence data in the analysis. The validity of the sequential reaction mechanism is examined.

Low-Lying States inSb122from theSn122(p,n)Reaction

The low-lying level structure of $^{122}\mathrm{Sb}$ is studied through the observation of coincident $\ensuremath{\gamma}$ rays following the $^{122}\mathrm{Sn}(p,n)$ reaction using two Ge(Li) detectors. Thirteen 1024-channel coincidence $\ensuremath{\gamma}$-ray spectra were obtained simultaneously in a PDP-7 computer by means of a two-parameter program. High-resolution singles spectra taken with a small-volume thin-window Ge(Li) detector (full width at half maximum approximately 0.6 keV at 121 keV) were also helpful in determining a level scheme for $^{122}\mathrm{Sb}$. A ($d,p$) experiment was also performed in order to gain additional information. The information obtained from the ($p,n$) reaction was combined with existing $^{121}\mathrm{Sb}(d,p)$ and $^{121}\mathrm{Sb}(n,\ensuremath{\gamma})$ data in constructing a proposed level scheme for $^{122}\mathrm{Sb}$.

Level structure in 152Gd studied in the decay of 17.5 h 152Tb

The decay of 152Tb(17.5 h) has been studied using Ge(Li) detectors to obtain singles spectra and to perform γ-γ coincidence experiments. More than 290 transitions are observed, of which about 100 were not previously reported. A revised decay scheme is proposed in which most of the observed transitions are attributed to the decay of 67 proposed states in 152Gd. Experimental internal-conversion coefficients are calculated using previously reported conversion-electron intensities and the γ-ray intensities obtained in this investigation. Branching ratios are compared to those obtained for analogous levels in other transitional nuclei, and an attempt is made to interpret the known level structure of 152Gd in terms of quasirotational bands. Quasi β, γ, βγ and 2β bands, as well as K = 0 and K = 1 octupole bands, are proposed. A level at 1862.0 keV is interpreted as the 2 + member of a possible quasi 3β band while a 2 + state at 1941.2 keV is interpreted as the bandhead of a possible quasi (γ-2β) band.

In-beam study of prompt γ-rays emitted in the 66Zn(p, nγ) 66Ga reaction

The level structure of the nucleus 66Ga has been studied by means of the 66Zn(p, nγ) 66Ga reaction ( Q = −5.957 MeV). Levels in 66Ga up to 730 keV in excitation were selectively populated by varying the proton bombarding energy in the range of 6.00 to 6.82 MeV. The γ-rays associated with these levels were identified both in singles spectra, from a study of their threshold behaviour, and inγγ-coincidence measurements. Altogether 24 levels in 66Ga were identified, of which 10 are known from previous studies of the β + decay of 66Ge to 66Ga, and the remaining 14 are reported here for the first time. Gamma-ray branching ratios for these new levels have been determined and a decay scheme comprising 68 γ-transitions is presented. Angular distributions of de-excitation γ-rays have been measured at proton bombarding energies close to threshold for the levels studied. Comparison of these distributions with the theoretical predictions of the compound nucleus statistical model has led to spin and parity assignments for the levels studied.