A γ-ray cascade in ${}_{}{}^{192}{}_{}{}^{}\mathrm{Hg}$ consisting of seventeen members is reported. The transition spacing is characteristic of a superdeformed band, and we propose it to be the second instance of superdeformation in the Hg region. We find the lowest spin in the band likely to be 8ħ using a new method for obtaining spins in some superdeformed nuclei.

Theoretical calculations are presented for the reaction ${\nu }_{\mathit{e}}$${+}^{12}$C${\to }^{12}$${\mathrm{N}}_{\mathrm{g}.\mathrm{s}.\mathrm{}}$ +${\mathit{e}}^{\mathrm{-}}$ for ${\mathit{E}}_{\nu }$ from threshold to 135 MeV, for the reaction ${\nu }_{\mathrm{\mu }}$${+}^{12}$C${\to }^{12}$${\mathrm{N}}_{\mathrm{g}.\mathrm{s}.\mathrm{}}$ +${\mathrm{\mu }}^{\mathrm{-}}$, and the corresponding antineutrino reaction for ${\mathit{E}}_{\nu }$ from threshold to 160 MeV. Use is made of updated form factors based on more recent data for ${\mathit{e}}^{\mathrm{-}}$${+}^{12}$C${\to }^{12}$${\mathrm{C}}^{\mathrm{*}}$+e’ - and γ${+}^{12}$C${\to }^{12}$${\mathrm{C}}^{\mathrm{*}}$. The recent neutrino reaction experiments are discussed in light of these calculations.

The Bonn meson-exchange NN potential is made applicable to pp scattering. Its predictions are compared with a variety of pp scattering observables for energies below the pion-production threshold. The resulting ${\chi }^2$ for the world pp data in the energy range 3–300 MeV is 1.72 per data point.

The total nuclear reaction probabilities for 27–92 MeV α particles stopping in Si were measured in coincidence studies of α-d elastic scattering. These probabilities are proportional to α-particle range and extrapolate to 2.07% at 100 MeV. They are adequately described both by calculations using Satchler’s optical model parameters and by the assumption of an energy-independent reaction cross section of 1170±55 mb. They are less well fitted by the Rebel optical model parameters and by predictions of semiclassical theory.

A comprehensive relativistic treatment of polarization observables in deuteron photo- and electrodisintegration is presented from a unified standpoint. A discussion of necessary and sufficient measurements needed for a complete determination of all transition amplitudes is given.

Cluster emission yields from ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ reactions on Ag targets are analyzed using Hauser-Feshbach theory with the hybrid preequilibrium decay model. The importance of multiple chance cluster emission is investigated, as well as sensitivity to assumptions of ground-state versus excited cluster emission. The importance of sequential decay is explored qualitatively. Calculations using an equal fragment/residue temperature limit plus preequilibrium decay, and those using a ground-state cluster emission/preequilibrium decay assumption bracket the experimental excitation functions, however, with up to several orders of magnitude difference between these upper and lower limit results.

This paper is part of an extensive survey of neutron scattering from nuclei in the Os-Pt transition region. We present neutron differential scattering cross sections from ${}_{}{}^{192}{}_{}{}^{}\mathrm{Os}$ measured at 1.60, 2.52, and 3.94 MeV, as well as neutron total cross sections measured between 250 keV and 4.2 MeV. These data are analyzed via coupled-channels models to extract nuclear structure information; the cross sections are found to be quite sensitive to the relative signs and magnitudes of the reduced matrix elements that couple the scattering channels. We find that nuclear excitation amplitudes from our neutron scattering data are in good agreement with results from Coulomb excitation experiments, in contrast to earlier findings for ${}_{}{}^{194}{}_{}{}^{}\mathrm{Pt}$. Neutron scattering cross sections to ${}_{}{}^{192}{}_{}{}^{}\mathrm{Os}$ are best described by models that depict ${}_{}{}^{192}{}_{}{}^{}\mathrm{Os}$ as a γ-soft vibrator; they cannot be described with γ-rigid models. The neutron energy dependence of the strength of the real scattering potential is consistent only with mean-scattering fields whose energy dependencies reflect the dispersion relations which connect the real and imaginary parts of the scattering potential.

A calculation of energetic photon production in proton-nucleus reactions at intermediate bombarding energies is performed assuming the first chance nucleon-nucleon collisional mechanism. The elementary nucleon-nucleon bremsstrahlung amplitude is calculated within a meson exchange potential model which includes the one-body as well as the two-body current contributions. The results are in reasonable agreement with the recent data by the Grenoble group at the proton incident energy of $T_{\mathrm{lab}}$=168 MeV and indicate that these energetic photons are created in a relatively low-density region in the nucleus (∼40% of the nuclear matter normal density). The present model, however, cannot account for the strong angular dependence observed at $T_{\mathrm{lab}}$=72 MeV.

Differential cross sections have been measured for the scattering of 8 MeV neutrons from ${}_{}{}^{190}{}_{}{}^{}$,192Os and ${}_{}{}^{194}{}_{}{}^{}\mathrm{Pt}$. These measurements have been combined with information from other neutron scattering experiments to fix accurately the electric quadrupole and octupole excitations strengths for low-lying levels. Comparison of this information with electromagnetic excitations for these same nuclei elucidates the rapidly evolving behavior of low-lying collective structures in Pt and Os nuclei. The ${}_{}{}^{194}{}_{}{}^{}\mathrm{Pt}$ excitations are those of a nucleus with a potential energy surface very soft to nonaxial deformations. On the other hand, the scattering cross sections for excited levels of ${}_{}{}^{190}{}_{}{}^{}\mathrm{Os}$ show evolution of excitations toward those of a nucleus vibrating about a prolate equilibrium shape.

An expression for photon transmission coefficients in the resonance regions was given, which consists of three parts corresponding to the statistical model, radiative capture in the compound elastic scattering channel, and radiative capture in the inelastic scattering channel, respectively. The last two mechanisms as well as the direct-semidirect capture are classified in the nonstatistical category. The radiative neutron capture for 13 even-neutron nuclides in the 3s mass region were investigated in the resonance energy range less than 3 MeV. The present studies show that it is possible to reproduce the measured capture cross sections and gamma-ray spectra reasonably, provided both the statistical and nonstatistical contributions are taken into account. Among the four mentioned nonstatistical mechanisms, the contribution from the radiative capture in the compound elastic scattering channel is dominant, which shows the positive correlations with the neutron strength function and the (d,p) spectroscopic factors in the final states; the maximum nonstatistical fraction is about 30%. No prominent even-odd effect of the proton number was observed.

The thermalization of the composite system created in the fusion of two heavy ions at an incident energy of 20–30 MeV/nucleon and the emission of fast nucleons before the attainment of statistical equilibrium are described by means of the Harp-Miller-Berne master equation approach. The incident energy is transformed into excitation energy by two-body nucleon-nucleon interactions, assuming that the mean field readjusts itself instantaneously as the two ions fuse. Symmetric and asymmetric systems have been investigated. The results indicate the paramount importance, in the case of symmetric systems, of interactions between high-energy nucleons, one of which scatters to a deep-hole state, thus producing the higher-energy particles observed experimentally.

Angular momentum distributions ${\sigma }_l$ for the compound nucleus ${}_{}{}^{164}{}_{}{}^{}\mathrm{Yb}$ were deduced from measurements of γ-ray multiplicity for all significant evaporation residues from fusion of ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$ and ${}_{}{}^{100}{}_{}{}^{}\mathrm{Mo}$. At the lowest bombarding energies the ${\sigma }_l$ extend to higher l values than do predictions of barrier-penetration models that include coupling of the principal inelastic channels, even if the coupling strengths are increased to match the experimental excitation function. Likewise, ${\sigma }_l$ from a real potential with an energy-dependent shape fitted to the excitation function fails to reproduce the experimental ${\sigma }_l$ distribution. Better success is achieved with models in which fusion occurs at large distances.

Neutron-unbound states in light fragments have been observed in ${}_{}{}^{14}{}_{}{}^{}\mathrm{Ag}$ reactions at 35 MeV/nucleon. The energy and the width of these states can be determined using a fragment-neutron coincidence technique. We report the energy and width for a state in ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$ (E=19.234±0.012 MeV, Γ=210±35 keV) and a state in ${}_{}{}^9{}_{}{}^{}\mathrm{Li}$ (E=4.296±0.015 MeV, Γ=60±45 keV).

An experimental test for the production of bound multineutron systems in the low center-of-mass energy environment of kinematically reversed heavy-ion reactions is described. The cross section for ${}_{}{}^{\mathrm{A}}{}_{}{}^{}\mathrm{n}$ production, where A≤5, is estimated to be <2 μb, integrated over angles, energies, and A.

The diffusivity of the nuclear surface plays an important role in peripherial collisions between two heavy ions. We show that a finite range force produces a diffuse surface for static nuclei in the Vlasov prescription. The surface is calculated self-consistently. This will allow us to perform more realistic calculations for peripheral reactions in the Boltzmann-Uehling-Uhlenbeck model.

Light charged fragments from the reactions ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$${+}^{51}$V at 35 MeV/nucleon and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{12}$C at 50 MeV/nucleon have been measured with a 4π array. Transverse collective motion is observed for all fragment types and increases in strength for the heavier fragments. The transverse momentum is qualitatively similar for the different impact parameters selected by the midrapidity charge. The global transverse momentum analysis includes corrections for correlations due to momentum conservation. The results are compared to those at higher energies to investigate whether the same or a new reaction phenomenon produces the collective motion. We outline some implications for the extraction of thermodynamic information from the kinetic energy of emitted fragments.

The evaporation residue cross sections for the fusion of the ${}_{}{}^{24}{}_{}{}^{}$Mg${+}^{24}$Mg system have been obtained at laboratory energies of 111, 160, and 206 MeV. Angular distributions of the evaporation residues were measured and used to determine the cross sections. These cross sections decrease at the higher energies, characteristic of a limiting angular momentum. Results are compared with the predictions of fusion-evaporation models and to the systematics known from other light heavy-ion systems. Evidence is presented for a contribution from incomplete fusion and for a possible contribution from the evaporation of ejectiles heavier than α particles to the fusion-evaporation cross section at 206 MeV.

We compare three test-particle methods currently used in numerical simulations of Boltzmann-type equations for the analysis of intermediate-energy heavy-ion collisions with an exact solution of the Krook-Wu model. These methods are the full ensemble, parallel ensemble, and hybrid techniques. We find that collisional relaxation is sensitive to the method of simulation used. The full ensemble approach is found to agree with the exact results of the Krook-Wu model. The parallel ensemble procedure provides a reasonable approximation to the analytical relaxation rate for a wide range of systems, while the hybrid method overestimates the relaxation rate. We further compare transverse flow data from the first two of these methods in a cascade simulation of heavy-ion collisions, and find reasonable agreement provided the two-body cross section is not enhanced by a large factor over its free space value. This has implications for quantitative comparisons of calculations to experimental data.

Previous analyses of the comparison of Weizsäcker-Williams theory to experiment for nucleon emission via electromagnetic excitations in nucleus-nucleus collisions have not been definitive because of different assumptions concerning the value of the minimum impact parameter. This situation is corrected by providing criteria that allow one to make definitive statements concerning agreement or disagreement between Weizsäscker-Williams theory and experiment.

Pre- and post-scission neutron multiplicities for the reaction ${}_{}{}^{169}{}_{}{}^{}\mathrm{Tm}$${(}^{36}$Ar,f) at $E_{\mathrm{lab}=205\mathrm{}}$ MeV were measured in coincidence with fission fragments of different masses and total kinetic energies. The mass and total kinetic energy dependence of the total neutron multiplicity as well as the width of the out-of-plane fission fragment correlation angle are well described by evaporation calculations. An average time before scission of several ${10}^{\mathrm{-}20}$ s is deduced from the average pre-scission neutron multiplicity. The mass dependence of the post-scission neutron multiplicity is consistent with an energy division at scission proportional to the mass of the fragments. For the first time clear evidence for an increase in pre-scission neutrons with increasing total kinetic energy values has been observed. Possible interpretations of this unexpected behavior are discussed.