The $\gamma$ decays of the two lowest $T=\frac{3}{2}$ states in ${\mathrm{Na}}^{21}$ at 8.97 and 9.22 MeV were studied as resonances in the ${\mathrm{Ne}}^{20}(p, \gamma )$ reaction by use of a gas cell and a 30-cc Ge(Li) detector. For the lower resonance, we find three branches: to the ${\frac{3}{2}}^{+}$ ground state (11%), to the ${\frac{5}{2}}^{+}$ first excited state (50%), and to the ${\frac{7}{2}}^{+}$ second excited state (39%). These results imply that $J={\frac{5}{2}}^{+}$ for the $T=\frac{3}{2}$ state. On the simple rotational model, transitions from states of the $K=\frac{1}{2}$ (Nilsson orbit #6) band are possible only to the ground-state $K=\frac{3}{2}$ (#7) band. A $J={\frac{5}{2}}^{+}$, $K=\frac{1}{2}$ assignment for the lowest $T=\frac{3}{2}$ state fits the observed branching ratios. The second resonance decays predominantly to the ground state, and there is at most a 9% branch to the ${\mathrm{½}}^{+}$ state at 2.41 MeV. The second resonance is assigned $J={\frac{1}{2}}^{+}$, $K=\frac{1}{2}$. If the 2.41-MeV state is $K=\frac{1}{2}$ (#9), no transition to it is expected. On both resonances, transitions to higher excited states are obscured by background.

A new resonance method is described which is suited for the measurement of hyperfine interactions at nuclear isomers with mean lives longer than 1 μsec. The method is characterized by pulsed-beam production of excited nuclei, the Larmor frequency of which is determined by a coherent superposition of the perturbed angular correlation originating from different beam pulses. An experiment was performed on a 4-μsec state of ${}_{}{}^{69}{}_{}{}^{}\mathrm{Ge}$. The $g$ factor was determined as $g=-0.2224\mathrm{}\pm 0.0007$.

Excitation and kinetic energies of prompt-fission fragments are predicted by considering a renormalized Fermi-gas model (RGM) and the concept of the potential-energy surface (PES). Our RGM treats the residual nuclear interactions as energy corrections on the free-gas Fermi surface. The ground-state RGM corrections of the fragments over those of the fissioning nucleus give directly a part of the fragment excitation energy and reproduces the shape of the prompt-neutron yield curve. The remaining part of the excitation is obtained from the change of the deformation-dependent part of the PES evaluated at the scission point. The total energy released in fission is also found from the PES. The kinetic energy is estimated from the conservation of energy. All predicted energies agree well with experiments in the thermal-neutron-induced fission of ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ and ${}_{}{}^{239}{}_{}{}^{}\mathrm{Pu}$.

Mica track detectors were used to detect recoil nuclei from the reactions of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, and ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ projectiles with Cu, Ag, Au, and Bi targets. The observed track-length distributions and angular distributions together with detector-threshold information indicate that the observed recoils result from complete fusion of the target and projectile nuclei. The cross section ${\sigma }_{\mathrm{CF}}$ for the complete fusion mechanism is found to be well below the total-reaction cross section ${\sigma }_R$ at the higher projectile energies. A sharp-cutoff model is employed to extract values of $J_{\mathrm{crit}}$, the maximum angular momentum of the compound nuclei formed in complete-fusion reactions. Using those values, complete-fusion cross sections are calculated as a function of the mass of the complete-fusion product for reactions induced by${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$, and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$. Assuming only first-chance fission, the ratio $\frac{{\Gamma }_f}{{\Gamma }_n}$ has been calculated for the system ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$+${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$→${}_{}{}^{213}{}_{}{}^{}\mathrm{Fr}$*.

An experiment has been carried out to study the $\gamma$ rays from the fission fragments of ${\mathrm{Cf}}^{252}$. The $Z$ values of the fragments studied were determined by detecting their $K{\alpha }_1$ x rays with a Si(Li) x-ray speectrometer. A single-channel analyzer was used to accept only pulses corresponding to the $K{\alpha }_1$ x rays of the element under study. The $\gamma$ rays were detected with a Ge(Li) detector, and a time coincidence system was used to accept only the $\gamma$-ray pulses that occurred within 0.175 μsec of the preselected x ray. Energy transitions in three fission elements, $\mathrm{La}\mathrm{}(Z=57\mathrm{})\mathrm{}$, $\mathrm{Ce}\mathrm{}(Z=58\mathrm{})\mathrm{}$, and $\mathrm{Pr}\mathrm{}(Z=59\mathrm{})\mathrm{}$, were observed in an energy range 125-300 keV. Eleven $\gamma$ transitions were seen in La, fourteen in Ce, and four in Pr, although some of the weaker $\gamma$ rays attributed to La and Pr may belong to $\mathrm{Ba}\mathrm{}(Z=56\mathrm{})\mathrm{}$ and $\mathrm{Nd}\mathrm{}(Z=60\mathrm{})\mathrm{}$, respectively.

Internal-conversion-coefficient and directional correlation measurements were used to determine the penetration parameter $\lambda$ for the 81-, 161-, and 303-keV transitions of ${}_{}{}^{133}{}_{}{}^{}\mathrm{Cs}$. The following internal-conversion coefficients were measured: ${\alpha }_K\mathrm{}\left(356\right)=0.020\mathrm{}\pm 0.001$, ${\alpha }_K\mathrm{}\left(303\right)=0.039\mathrm{}\pm 0.002$, ${\alpha }_K\mathrm{}\left(161\right)=0.21\mathrm{}\pm 0.02$, ${\alpha }_K\mathrm{}\left(81\right)=1.46\mathrm{}\pm 0.05$, and ${\alpha }_{L+M+N}\mathrm{}\left(81\right)=0.314\mathrm{}\pm 0.020$. Existing $L$-, $M$-, and $N$-shell relative intensities of the 81-keV transition were used with ${\alpha }_{L+M+N}\mathrm{}\left(81\right)\mathrm{}$ to deduce the following subshell coefficients: ${\alpha }_{L_{\mathrm{I}}}\mathrm{}\left(81\right)=0.196\mathrm{}\pm 0.020$, ${\alpha }_{L_{\mathrm{II}}}\mathrm{}\left(81\right)=0.029\mathrm{}\pm 0.004$, ${\alpha }_{L_{\mathrm{III}}}\mathrm{}\left(81\right)=0.022\mathrm{}\pm 0.004$, and ${\alpha }_{M_{\mathrm{I}}}\mathrm{}\left(81\right)=0.044\mathrm{}\pm 0.009$. The $\frac{K}{\mathrm{}(L+M)\mathrm{}}$ conversion ratios of the 276- and 161-keV transitions were measured as 4.75±0.15 and 3.75±0.25, respectively. The following directional correlation functions were measured: $W(356\mathrm{}\gamma -81\mathrm{}\gamma )=1+(0.0355\mathrm{}\pm 0.0037)P_2\left(cos\theta \right)+(0.000\mathrm{}\pm 0.008)P_4\left(cos\theta \right)$, $W(276\mathrm{}\gamma -161\mathrm{}\gamma )=1-(0.420\mathrm{}\pm 0.009)P_2\left(cos\theta \right)-(0.028\mathrm{}\pm 0.010)P_4\left(cos\theta \right)$, $W(276\mathrm{}\gamma -161\mathrm{}{e_K}^{-})=1-(0.256\mathrm{}\pm 0.020)P_2\left(cos\theta \right)-(0.090\mathrm{}\pm 0.025)P_4\left(cos\theta \right)$. The following directional correlation coefficients were also measured: $A_2(276\mathrm{}{e_K}^{-}-161\mathrm{}\gamma )=-0.7\mathrm{}\pm 0.1$ and $A_2(303\mathrm{}{e_K}^{-}-81\mathrm{}\gamma )=0.003\mathrm{}\pm 0.008$. Using the above body of data, the following penetration parameters were determined: $\lambda \mathrm{}\left(81\right)=2.8\mathrm{}\pm 2.3$, $\lambda \mathrm{}\left(161\right)=41\mathrm{}\pm 6$, and $\lambda \mathrm{}\left(303\right)=-{{2.0}_{-3.1\mathrm{}}}^{+3.3\mathrm{}}$. The retardation factors for the $M1\mathrm{}$ components of the 81- and 161-keV transitions were reevaluated as ∼420 and ∼230, respectively.

The $A_2$ coefficients in the directional correlation between the nonunique first forbidden 0.935-MeV $\beta$ group and the 0.137-MeV $\gamma$ ray in the decay of ${}_{}{}^{186}{}_{}{}^{}\mathrm{Re}$, and in the directional correlation between the nonunique first forbidden 1.980-MeV $\beta$ group and the 0.155-MeV $\gamma$ ray in the decay of ${}_{}{}^{188}{}_{}{}^{}\mathrm{Re}$, have been measured as a function of energy. An investigation of perturbation caused by a magnetic hfs-type interaction yielded a negative result. Both of these $\beta$ spectra were found to have the "allowed" shape over the region examined.

The $\gamma$-ray spectrum from the decay of ${}_{}{}^{132}{}_{}{}^{}\mathrm{I}$ was measured with small- and large-volume, high-resolution Ge(Li) detectors, and 116 transitions were assigned in its decay. Selected regions of the conversion-electron spectrum were measured with an iron double-focusing spectrometer. The $K$-conversion coefficient of the 772-keV transition that was measured relative to the $K$-conversion coefficient of the 662-keV transition in ${}_{}{}^{137}{}_{}{}^{}\mathrm{Ba}$ was used to normalize the electron and $\gamma$ spectra to obtain the $K$-conversion coefficients of the 262.7-, 284.7-, 505.9-, 522.6-, 621.0-, 630.2-, 650.6-, 669.8-, 671.5-, 727.1-, 809.8-, 812.3-, 954.6-, 1136.0-, 1143.4-, 1173.2-, 1372.1-, and 1398.6-keV transitions. Conversion coefficients of additional transitions were obtained from electron intensities of other work. From these conversion coefficients, each of the above transitions was assigned an $M1\mathrm{}$ and/or $E2\mathrm{}$ multipolarity.

Two-parameter, 4096×4096, $\gamma -\gamma$ coincidence measurements have been carried out to establish the energy levels and placement of new $\gamma$ rays observed in the decay of ${}_{}{}^{132}{}_{}{}^{}\mathrm{I}$ to ${}_{}{}^{132}{}_{}{}^{}\mathrm{Xe}$. A NaI-Ge(Li) detector arrangement with a ND 3300 system was used. Spectra from the Ge(Li) detector in coincidence with 60-keV-wide NaI gates centered at 515, 630, 772, 800, 954, 1110, and 1170 keV and 120-keV-wide gates centered at 1270 and 1410 keV were analyzed. These data were used to place 63 transitions into a scheme with the following energies (in keV), spins, and parities: 667.67, 2+; 1297.84, 2+; 1440.27, 4+; 1803.66, 3+; 1962.92, (3, 4) +; 1985.3, 2(+); 2110.18, (3, 4) +; 2111.8, (5, 6) +; 2350.67, (3-5); 2394.93, (3, 4) +; 2424.89, (3.4) +; 2583.75, (3-5) +; 2588.66, (3, 4); 2613.50, (3-5) +; 2669.95, (3, 4) +; 2754.43, (3, 4); 2838.70, (3-5) +; 2840.29, (3, 4) +; 2890.74, (3, 4); and 3058.17, (3,4). Each level is based on observed coincidence relations. A tentative level assignment was also made for a 2041-keV (5—) level. An additional 10 levels are required by unplaced high-energy transitions.

The need for accurate measurements of the total yield of neutrons ($\nu$) in spontaneous fission of ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$ has continued. Such a measurement, incorporating advances over previous work, has been accomplished with a high degree of authentication. The yield was determined by separate direct evaluations of the neutron rate and fission rate of three fission-fragment counters plated with ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$. The neutron emission-rate factor in the yield was found with the aid of a manganese-bath facility independently calibrated with reference to absolute $\beta -\gamma$ coincidence counting of ${}_{}{}^{56}{}_{}{}^{}\mathrm{Mn}$. Special measurements were also made of other subsidiary parameters, while precise support in the accuracy of neutron assay was obtained from comparisons with international standard sources. The fission rate was derived primarily from absolute fission-neutron coincidence data obtained from the fission counters, with special attention to angular-correlation effects. The resulting value of $\nu \left({}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}\right)=3.725\mathrm{}\pm 0.015$ (total yield) is generally independent of cross sections, neutron spectrum assumptions, counting statistics, and fission-fragment self-absorption. The error assigned is a combination of statistical and systematic effects at a confidence level of 68%. Two unverified correction factors have been isolated.

The effect of angular momentum on compound-nucleus reactions was investigated by measuring the formation cross-section ratios of the isomers of tellurium-119. Nine reactions were studied. Five proceeded via the compound nucleus ${}_{}{}^{122*}{}_{}{}^{}\mathrm{Te}$, and two each via the compound nuclei ${}_{}{}^{121*}{}_{}{}^{}\mathrm{Te}$ and ${}_{}{}^{123*}{}_{}{}^{}\mathrm{Te}$. Projectiles ranging in size from ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ to ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ were employed. The experimentally determined ratios (upper-state to lower-state) varied from about 0.75 to 25. The expected increase of ratio with energy and projectile size was verified. An apparent direct interaction of ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ projectiles was observed. Calculations of a simple type which considered only the angular momentum distribution of the compound nucleus, and calculations of the Huizenga-Vandenbosh type were performed for the reactions studied.

Neutron transmission coefficients are determined experimentally by investigation of the neutron decay of isobaric analog resonances (IAR) in the compound nucleus. Assuming a statistical decay of the IAR, the neutron branching ratios to the different final states are determined by the transmission coefficients of the partial waves allowed by angular momentum and parity conservation. Therefore, knowing the spin and the parity of the resonance and of the final states, the transmission coefficients can be obtained from the measured decay rates. This method is applied to the ${}_{}{}^{91}{}_{}{}^{}\mathrm{Zr}(p, n){}_{}{}^{91}{}_{}{}^{}\mathrm{Nb}$ reaction. The decay of two pronounced IAR in ${}_{}{}^{92}{}_{}{}^{}\mathrm{Nb}$ at $E^{*}=4.70\mathrm{}$ MeV ($4^{+}$) and $E^{*}=5.30\mathrm{}$ MeV ($2^{+}$) is studied by the time-of flight method. The measured transmission coefficients are compared with calculations, using two different optical-model parameter sets. Agreement for all partial waves is obtained by modifying the parameters of Moldauer, Engelbrecht, and Fiedeldey.

The inelastic scattering of 20-MeV tritons from ${}_{}{}^{92}{}_{}{}^{}\mathrm{Zr}$, ${}_{}{}^{94}{}_{}{}^{}\mathrm{Zr}$, and ${}_{}{}^{96}{}_{}{}^{}\mathrm{Zr}$ has been studied. The principal objective was to obtain an effective interaction strength to be used in a microscopic description of the excitation of neutron states. Only the lower levels of ${}_{}{}^{92}{}_{}{}^{}\mathrm{Zr}$ and ${}_{}{}^{94}{}_{}{}^{}\mathrm{Zr}$ were studied, but because of the paucity of available data on ${}_{}{}^{96}{}_{}{}^{}\mathrm{Zr}$, this isotope is studied in a more complete way, with 28 levels and 17 spins assigned. The shell-model results indicate a much smaller effective interaction strength for the excitation of neutron states than noted earlier for proton states in triton inelastic scattering.

The differential cross sections for the elastic scattering of 1.33-MeV photons from lead and uranium have been remeasured at angles ranging from 60° to 135°, using a lithium-drifted germanium detector. Dispersion relations are used to fix the relative phases among nuclear Thomson, Rayleigh, and Delbrück scattering. These relative phases and the calculations of the amplitudes for the individual scattering processes permit the theoretical cross sections to be determined. A discrepancy exists between the theoretical calculations and the experimental results. Previous suggestions for removing this discrepancy include incoherence between scattering from the nucleus and from the electrons, and a 180° phase shift between the parallel-polarization components of the nuclear Thomson and Rayleigh amplitudes. These suggestions are discussed and another possibility, destructive interference at large angles between Rayleigh scattering from the $K$ shell and from the $L$ shell, is presented.

The $\alpha$ decay of ${}_{}{}^{212g}{}_{}{}^{}\mathrm{At}$ and ${}_{}{}^{212m}{}_{}{}^{}\mathrm{At}$ to excited states of ${}_{}{}^{208}{}_{}{}^{}\mathrm{Bi}$ has been measured. Half-lives of 0.315±0.003 and 0.122±0.001 sec were determined in agreement with previous work. Out of a possible 28 transitions, 20 $\alpha$ transitions were observed to states in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Bi}$ below 1.11-MeV excitation.

A polarized-neutron transmission method is used to determine the shift of the neutron resonance energies due to the hyperfine interaction of the compound states. Resonances in ${\mathrm{Er}}^{167}$+$n$ at 0.460 and 0.584 eV are investigated. The resonance at 0.584 eV ($J=I-\frac{1}{2}$) shows a strong effect, leading to a very large value of the $g_J$ factor, while $g_J$ for the 0.460-eV resonance ($J=I+\frac{1}{2}$) is in the order of $g_I$ for the ${\mathrm{Er}}^{167}$ ground state. The results are compared to some recent predictions based on a statistical model of the compound nucleus. The role of nuclear magnetic interference terms which lead to a strong background transmission effect is discussed.

Coulomb excitation of the first $2^{+}$ state in ${}_{}{}^{142}{}_{}{}^{}\mathrm{Ce}$ was produced by 42-MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ ions. The static quadrupole moment of the first $2^{+}$ excited state and the $B(E2, 0^{+}\to 2^{+})$ were determined. The values were $-0.12\mathrm{}\pm 0.09 e$ b and $0.459\pm 0.006 e^2$ ${\mathrm{b}}^2$, respectively.

An accurate absolute measurement of the longitudinal polarization of conversion electrons is reported. The investigation was stimulated by a suggestion of Mendels and Wouthuysen on a possible electron polarization in electromagnetic processes. The measurements confirm the general belief that conversion electrons from unoriented sources are not polarized. We found for the $K$- and $L$-conversion lines of ${}_{}{}^{114m}{}_{}{}^{}\mathrm{In}:P_c\mathrm{}\left(K\right)=-0.001\mathrm{}\pm 0.008$ and more accurately: $P_c\mathrm{}\left(L\right)=+0.001\mathrm{}\pm 0.004$.

The ${}_{}{}^{241}{}_{}{}^{}\mathrm{Am}$ spontaneous-fission decay constant has been determined with solid-state track recorders of preetched mica. Measurements have been carried out with electroplated ${}_{}{}^{241}{}_{}{}^{}\mathrm{Am}$ sources. Consistent spontaneousfission-rate measurements have been obtained for a large range of fission track densities over more than a 3-yr period. Systematic error due to source impurities has been established as insignificant relative to statistical error. The present experimental result for the ${}_{}{}^{241}{}_{}{}^{}\mathrm{Am}$ spontaneous-fission decay constant is ${\lambda }_f=(6.04\mathrm{}\pm 0.13)\times {10}^{-15\mathrm{}}$ ${\mathrm{yr}}^{-1\mathrm{}}$.

Contrary to the conclusions reached in a recent paper, we find that for the usual combination of long-range and pairing force that is used for calculations in heavy nuclei, the Belyaev-Inglis formula for moment of inertia is adequate and gives values close to those obtained from projection methods.