The elastic scattering of 48 MeV $\alpha$ particles by ${}_{}{}^{62,64}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{63,65}{}_{}{}^{}\mathrm{Cu}$, and ${}_{}{}^{64,66}{}_{}{}^{}\mathrm{Zn}$ is optical-model analyzed. The $\overrightarrow{\mathrm{I}}·\overrightarrow{\mathrm{L}}$ potential depth is found to be much weaker than reported in previous optical-model analysis.

[NUCLEAR REACTIONS ${}_{}{}^{62,64}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{63,65}{}_{}{}^{}\mathrm{Cu}$, ${}_{}{}^{64,66}{}_{}{}^{}\mathrm{Zn}(\alpha ,\alpha )$, $E=48\mathrm{}$ MeV; measured $\sigma \left(\theta \right)$, $\theta =18-{172}^{\circ }$; enriched targets; optical-model analysis.]

Experimental and theoretical evidence favors a spin-orbit symmetry potential which has a sign opposite to the corresponding term of the central potential. Only one of the potentials employed in recent calculations of the stability of superheavy elements is in accord with the sign. The shell correction term for the nucleus ${}_{}{}^{254}{}_{}{}^{}\mathrm{}\left(126\right)\mathrm{}_{228}^{}{}_{}{}^{}$ is changed by 2 MeV when an extrapolation based on the experimentally observed symmetry term is used rather than the standard extrapolation.

[NUCLEAR STRUCTURE Effect of the experimentally determined spin-orbit symmetry potential on the spherical shell correction term of superheavy elements.]

The decay of ${}_{}{}^{204}{}_{}{}^{}\mathrm{Bi}$($6^{+}$, 11.3 h) is found to populate a delayed $7^{-}$ state ($T_{\frac{1}{2}}=0.45\mathrm{}$ μs, $E^{*}=2264\mathrm{}$ keV) in ${}_{}{}^{204}{}_{}{}^{}\mathrm{Pb}$. A transition from this state accounts for 60% of the feeding of the well-known $9^{-}$ isomer at 2185 keV.

[RADIOACTIVITY ${}_{}{}^{204}{}_{}{}^{}\mathrm{Bi}$; measured $E_{\gamma }$, $I_{\gamma }$, $\gamma \gamma \mathrm{}\left(t\right)\mathrm{} {}_{}{}^{204}{}_{}{}^{}\mathrm{Pb}$; deduced levels, $J$, $\pi$, $T_{\frac{1}{2}}$.]

A microscopic formulation of the nucleon-nucleus imaginary inelastic form factor using particle-hole intermediate states gives a result which is roughly the real form factor times a function consisting of intermediate particle- and hole-scattering terms. These terms have opposite signs, allowing the possibility of a radial dependence for the form factor similar to the collective model. Numerical results for 30 MeV ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}(n,n^{\prime }){}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}(3^{-},3.73\mathrm{} \mathrm{MeV})$ scattering are compared with the collective model.

[NUCLEAR REACTIONS Inelastic scattering, microscopic calculation of imaginary form factor for ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}(n,n^{\prime }){}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}(3^{-},3.73\mathrm{} \mathrm{MeV})$.]

Effective excitation energies used to obtain level densities in statistical model deexcitation calculations of nuclei with high angular momenta have been evaluated specifically for neutron, proton, deuteron, and $\alpha$ emission. When particle emission is assumed to change the initial angular momentum distribution, the effect of these excitation energies is to strongly enhance $\alpha$ emission relative to other modes of deexcitation. Calculations are illustrated with reference to the deexcitation of the ${}_{}{}^{149}{}_{}{}^{}\mathrm{Tb}$ compound nucleus.

[NUCLEAR REACTIONS Deexcitation of compound nuclei. Statistical model. Fission and particle emission. Calculations for ${}_{}{}^{149}{}_{}{}^{}\mathrm{Tb}$.]

Angular momentum operator identities are used to show that Skyrme's expression can be written using the $y$ component of angular momentum only. It is shown that the Gaussian approximation for the matrix element of ${J_y}^4$ leads to the Peierls-Yoccoz expression. A new approximation based on the theory of probability is introduced. The numerical calculations for the $2s-1d$ shell nuclei show that the inverse of the inertia parameter using the statistical approximation is much closer to Skyrme's value than the one given by the Peierls-Yoccoz approximation.

[NUCLEAR STRUCTURE Approximations for nuclear inertia parameter.]

The mass of ${}_{}{}^{21}{}_{}{}^{}\mathrm{O}$ is measured as 8.153 ± 0.070 MeV from the $Q$ value of the ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$(${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{15}{}_{}{}^{}\mathrm{O}$)${}_{}{}^{21}{}_{}{}^{}\mathrm{O}$ reaction at 91 MeV.

[NUCLEAR REACTIONS ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$(${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{15}{}_{}{}^{}\mathrm{O}$), $E=91\mathrm{}$ MeV; measured ${}_{}{}^{21}{}_{}{}^{}\mathrm{O}$ mass. Enriched target.]

Parity violating nuclear forces polarize conversion electrons and lead to the up-down asymmetry in the angular distribution of the emitted electrons. Measurements of these processes can indicate which irregular parity-forbidden multipoles contribute to the transition. Effects are much smaller than conjectured in an earlier publication.

[RADIOACTIVITY Parity violation, polarization and asymmetry associated with internal conversion.]

The first-order correction to the closure approximation in the multiple-scattering calculation of the second-order optical potential is shown to vanish under rather general conditions.

[NUCLEAR REACTIONS Scattering theory. Optical potential. Multiple scattering. Nucleon-nucleus scattering.]

Recent ($\overrightarrow{p},{\pi }^{+}$) experiments on ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ at 200 MeV proton bombarding energy indicate that the production asymmetry $\epsilon$ cannot be explained (within the distorted-wave Born-approximation framework) by proton distortion alone. We examine in a simple model the effect of pion rescattering from the nucleus. The dependence of $\epsilon$ on the pion wave function, as well as its sensitivity to nuclear structure and the pion production operator are studied. The implication of the large negative asymmetry observed experimentally is briefly discussed.

[NUCLEAR REACTIONS Calculated asymmetries in ($\overrightarrow{\mathrm{p}},{\pi }^{+}$) reactions on ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ at $T_p=200\mathrm{}$ MeV.]

We have calculated the parity violating observables in $p-p$ and $n-p$ scattering using a number of strong nucleon-nucleon potentials for a large class of weak parity violating potentials.

[NUCLEAR REACTIONS $\mathrm{pp}$ and $\mathrm{np}$ low energy scattering; calculated parity violating observables $A_p$, $\mathrm{An}$, various strong and weak potentials.]

Gamma rays from the reaction ${}_{}{}^{76}{}_{}{}^{}\mathrm{Se} (p,n\gamma )$ ${}_{}{}^{76}{}_{}{}^{}\mathrm{Br}$ were observed at proton energies between 5.80 and 6.50 MeV. A total of 35 $\gamma$ rays were assigned to transitions in ${}_{}{}^{76}{}_{}{}^{}\mathrm{Br}$. A level scheme involving 15 levels up to an excitation energy of 616.3 keV was deduced from threshold measurements, energy sums, and $\gamma -\gamma$ coincidence studies. These results have resolved disagreements between two previous experiments involving the $\beta$-decay of ${}_{}{}^{76}{}_{}{}^{}\mathrm{Kr}$. Previously unreported levels have been assigned at 495.4, 505.0, 527.5, and 548.0 keV.

[NUCLEAR REACTIONS ${}_{}{}^{76}{}_{}{}^{}\mathrm{Se}(p,n\gamma )$, $E=5.80-6.50\mathrm{}$ MeV; measured $E_{\gamma }$, $I_{\gamma }$, $\gamma \gamma$ coin: ${}_{}{}^{76}{}_{}{}^{}\mathrm{Br}$ deduced levels. Enriched target, Ge(Li) detectors.]

Experimentally determined coefficients for a Fourier-Bessel description of the charge distribution of ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ are used as geometrical constraints in a single particle model analysis. Calculations are made using local and nonlocal potentials to fit both these coefficients and the level positions.

[NUCLEAR STRUCTURE ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$, calculated charge distribution, single-particle model. Fits to experimental Fourier-Bessel coefficients.]

An approximate amplitude for $n-d$ scattering has been constructed, which depends only on the on-shell two nucleon ${}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}$ and ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ amplitudes and their analytic continuation to negative energies as defined by a separable potential model. The theory has been tested by comparison with exact results, and has been found to be a good approximation for partial waves with $L\ge 2$, and for incident neutron lab energies up to about 14 MeV.

[NUCLEAR REACTIONS $n-d$ scattering; low energies; high partial waves; on-shell theory.]

In a study of the effect of the quantal zero-point oscillations of nuclei on their low-energy fusion cross section, we calculate exactly the penetrability for a simple two-dimensional barrier $V(r,\sigma )$. The coordinate $r$ is the distance between the centers of mass of the two nuclei, and $\sigma$ is the sum of the root-mean-square extensions along the symmetry axis of the matter distribution of each nucleus about its center of mass. The potential $V(r,\sigma )$ is a parabolic peak in $r$ and is one or the other of two harmonic oscillators in $\sigma$, depending upon whether $r$ is greater than or less than a critical value $r_1$. The oscillators differ both in the locations of their minima and in their curvatures. This simulates the dominant feature in the two-dimensional nuclear potential-energy surface of two misaligned valleys (the fission and fusion valleys) separated by a ridge between them. When an incident wave that is localized in the fusion valley encounters the potential-energy ridge, it is partially transmitted and partially reflected in waves that correspond to different excited states in the transverse direction and hence to different amounts of energy in the fusion direction. The amplitudes of these waves are determined by requiring that the wave functions (expressed exactly in terms of parabolic-cylinder functions) and their first derivatives be continuous at $r_1$. The penetrability is then obtained from the amplitudes of the transmitted waves. As a specific example, we use this formalism to calculate the penetrability for a two-dimensional potential-energy surface appropriate to the reaction ${}_{}{}^{100}{}_{}{}^{}\mathrm{Mo}$ + ${}_{}{}^{100}{}_{}{}^{}\mathrm{Mo}$ → ${}_{}{}^{200}{}_{}{}^{}\mathrm{Po}$. The calculated penetrability is substantially different from the result for a one-dimensional calculation. In particular, 10 MeV below the maximum in the one-dimensional fusion barrier the two-dimensional penetrability is ${10}^{10}$ times as large as the one-dimensional result. Also, for equal penetrability the slopes of the two curves are very different.

[NUCLEAR REACTIONS Heavy-ion ${}_{}{}^{100}{}_{}{}^{}\mathrm{Mo}$+${}_{}{}^{100}{}_{}{}^{}\mathrm{Mo}$→${}_{}{}^{200}{}_{}{}^{}\mathrm{Po}$. Calculated exactly penetrability for simple two-dimensional fusion barrier. Heavy-ion fusion cross section, multidimensional-barrier penetration, parabolic-cylinder functions.]

Evaporation residues from the fusion reactions of 110 MeV ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ with ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ and 132 MeV ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ with ${}_{}{}^{70}{}_{}{}^{}\mathrm{Ge}$ were observed with the aid of an energy-mass spectrograph. The residues were resolved by mass number, and the masses observed in the ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ + ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ reaction were $A=84\mathrm{} (23\%\pm 5\%)$, $A=86\mathrm{} (27\%\pm 5\%)$, and $A=87\mathrm{} (50\%\pm 10\%)$. The ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ + ${}_{}{}^{70}{}_{}{}^{}\mathrm{Ge}$ reaction yielded $A=94\mathrm{} (14\%\pm 1\%)$, $A=95\mathrm{} (23\%\pm 1\%)$, $A=96\mathrm{} (14\%\pm 1\%)$, $A=97\mathrm{} (24\%\pm 1\%)$, $A=98\mathrm{} (21\%\pm 1\%)$, and $A=99\mathrm{} (5\%\pm 1\%)$. Angular distributions and velocity spectra were obtained for each mass, allowing partial reconstruction of the residues' kinematic history, and consequently of the particle evaporation modes leading to each residue. Average particle energies and anisotropies for each residue mass may be inferred from comparison with a Monte Carlo simulation of the evaporation process. The results are discussed and compared with calculations made with the aid of a statistical model evaporation code.

[NUCLEAR REACTIONS ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$(110 Me${\mathrm{V}}_{1\mathrm{a}\mathrm{b}}$) + ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ fusion, ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$(132 Me${\mathrm{V}}_{1\mathrm{a}\mathrm{b}}$) + ${}_{}{}^{70}{}_{}{}^{}\mathrm{Ge}$ fusion; mass spectra, angular distributions, velocity spectra, and relative total cross sections for evaporation residues.]

Resonance parameters for four resonances in Si have been obtained by analyzing measured differential neutron scattering cross sections combined with the total neutron cross section in the neutron energy range 1.05-1.40 MeV and applying $R$ — matrix single channel multilevel theory. The resonance at 1254 keV has been identified as the $s$ — wave analog resonance in ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$. The identification also takes into account experimental radiative neutron capture data and shell model calculations for the radiative width. Estimates of the isospin mixing matrix elements are given.

[NUCLEAR REACTIONS ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}\mathrm{}\left(n\right)\mathrm{}$, ($n,n$), $E_n=1.05-1.40\mathrm{}$ MeV, measured ${\sigma }_{\mathrm{nt}}\mathrm{}\left(E\right)\mathrm{}$, $\sigma \mathrm{}\left(E\right)\mathrm{}$, $\sigma (E,\theta )$. $R$ matrix analyses, ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$ deduced resonances, $J$, $\pi$, $\Gamma$. Isobaric analog isospin impurities.]