The ${}_{}{}^{95}{}_{}{}^{}\mathrm{Ru}$ nucleus has been studied through the ${}_{}{}^{94}{}_{}{}^{}\mathrm{Mo}$(α,3n${)}^{95}$Ru reaction. A level scheme has been proposed from γ-γ coincidence data and spin assignments are made on the basis of the results of angular distribution measurements. A rotation-particle coupling calculation has been performed and the proposed level scheme is discussed in the light of its predictions. The results obtained in the present work are also compared to those of previous investigations on this nucleus.

From a partitioning of the valence shell space in terms of the valence proton and neutron particle and hole boson subspaces, a systematic dependence of the γ-g interband B(E2) ratios on the ${\mathit{N}}_{\mathit{p}}$${\mathit{N}}_{\mathit{n}}$ product is obtained. Limitations of ${\mathit{N}}_{\mathit{p}}$${\mathit{N}}_{\mathit{n}}$ to yield an expected smooth behavior of these ratios with hole-particle symmetry, and ${\mathit{N}}_{\mathit{p}}$, ${\mathit{N}}_{\mathit{n}}$ symmetry assumed in interacting boson model-1 as well as in individual cases are demonstrated.

The scissor mode was applied to the yrast rotational band of the rare-earth even-even nuclei from ${}_{}{}^{152}{}_{}{}^{}\mathrm{Gd}$ to ${}_{}{}^{192}{}_{}{}^{}\mathrm{Os}$. The quadrupole deformations and backbending and forebending effects are well explained. This approach shows that the uppermost angular momentum of the G band exists and the superband and G band are made on the basis of the scissor mode. It is thought that this classical approach of the interacting boson model II can be reasonable in order to explain the low-lying energy levels of the rare-earth nuclei.

The particle-rotor model has been applied to calculate the band structure in a number of highly neutron deficient odd-A rare-earth nuclei in the A≃130–150 region. Several transitional nuclei are also included in the study. The only adjustable parameter, used in the calculation, is the Coriolis attenuation coefficient. However, it is seen that the observed band structures in these nuclei can be reproduced practically without any ad hoc reduction of the Coriolis matrix elements. The systematics of the Coriolis attenuation in the neutron-deficient, transitional, and well-deformed rare-earth nuclei are discussed in the light of the present work and several theoretical studies, made earlier. The importance of the pairing interaction in the Coriolis attenuation study is emphasized.

Systematic potential-energy-surface (PES) and cranked-shell-model (CSM) calculations have been performed for nuclei in the A≊120–140 mass region using the newly fitted Nilsson potential (κ,μ) parameters. The roles of the ${\mathit{h}}_{11/2}$ quasiparticles in the onset of nuclear deformation and rotational alignment are explored. The PES calculations predict prolate-oblate energy-difference curves for several odd-proton nuclei which suggest the coexistence of oblate and prolate ${\mathit{h}}_{11/2}$ single quasiproton states. A major conclusion of this work is that the newly fitted Nilsson potential (κ,μ) parameter sets result in calculated rotational band-crossing frequencies that are in good agreement with experimental proton alignment in addition to reproducing the bandhead energies of odd-Z nuclei in this mass region.

Transition charge densities of inelastic electron scattering for the excitation of $2^{+}$ and $4^{+}$ states in even-mass Ni isotopes are investigated in terms of the standard shell model of the (${\mathit{p}}_{3/2}$,${\mathit{p}}_{1/2}$,${\mathit{f}}_{5/2}$${)}^{\mathit{n}}$ configurations. Effective transition operators pertinent to the model space are derived by considering particle-hole excitations up to 12ħω for C2 and 14ħω for C4 transitions within the framework of a first-order perturbation theory. It is shown that surface-peaked transition charge densities can be obtained for the first excited $2^{+}$ and $4^{+}$ states, being in agreement with experiment. Particle-hole excitations up to λħω, e.g., λ=2 for C2 transition, are most responsible for that feature. Higher ħω excitations appear relatively significant in the interior region of the nucleus: They enhance the peak around the surface, improving further agreement with experiment, but for C2 transition they tend to generate another peak inside the nucleus and thus seem to deteriorate agreement with experiment. Transition densities for the $0_{\mathrm{g}.\mathrm{s}.\mathrm{}}^{+}$→$2_{2,3}^{+}$ and $0_{\mathrm{g}.\mathrm{s}.\mathrm{}}^{+}$→$4_2^{+}$ transitions are also discussed.

In the single j shell approximation, only the isovector amplitudes of electron-nucleus or proton-nucleus scattering contribute to the excitation of $1^{+}$ states from the J=$0^{+}$ targets of even-even nuclei, provided the excitation is a one-step process. However, when configuration mixing is put in, one also obtains contributions from isoscalar amplitudes, which are here studied for various nuclei in the f-p shell${–}^{44}$Ti, ${}_{}{}^{46}{}_{}{}^{}\mathrm{Ti}$, ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ti}$ and ${}_{}{}^{50}{}_{}{}^{}\mathrm{Cr}$. A comparison of the cross-conjugate pairs ${}_{}{}^{46}{}_{}{}^{}\mathrm{Ti}$ and ${}_{}{}^{50}{}_{}{}^{}\mathrm{Cr}$ is made. The decomposition of the electron-nucleus scattering into an orbital and spin part is made. The isoscalar effects are small and are unable to explain the discrepancies between the experimental analysis and the shell model calculations with regards to the variation of the orbit to spin ratio for various nuclei. However, there is probably hidden orbital strength in a state in ${}_{}{}^{50}{}_{}{}^{}\mathrm{Cr}$ for which the spin and orbit excitation amplitudes interfere destructively.

A relativistic nuclear mean field model is developed involving nucleons coupled to effective scalar and vector fields. It differs slightly from the usual Walecka model in the form of the coupling of the nucleon to the scalar meson. We calculate the equation of state for symmetric nuclear matter at zero temperature. The model, which has no arbitrary parameters, once we fit the empirical density and energy of nuclear matter, yields a compression modulus of 225 MeV and an effective nucleon mass=0.85.

A model of a superconducting phase transition is studied in terms of two competing dynamical symmetry chains. It is shown that a sharp phase transition occurs in the limit of large-dimensional representations and that, for finite representations, the smoothed-out phase transitions can be understood clearly in analytical terms. It is also shown, both numerically and analytically, that the Mottelson approximation becomes exact for large-dimensional representations.

From the cluster-model viewpoint, a problem of why the α-cluster structure persists in the ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ti}$ nucleus in spite of the strong spin-orbit force is resolved together with the departure from the rotational structure of the ground-band spectrum, in comparison with the ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$ and ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ nuclei.

Recently much effort has been spent to make the generator coordinator method applicable to problems concerning the dynamics of collective motion at high spin, which goes beyond the possibilities of standard mean field approaches. Using the so-called horizontal expansion, we report in this paper on first calculations about how fluctuations in the triaxial shape can affect the band crossing process among high-spin states in deformed nuclei. For the yrast band in ${}_{}{}^{184}{}_{}{}^{}\mathrm{Pt}$, we find that the neutron ${\mathit{i}}_{13/2}$ pair first starts to align smoothly, but is followed by a sharp alignment of a proton ${\mathit{h}}_{9/2}$ pair. These two rotational alignment processes take place in a frequency range where there is a strong mixture of shapes with different γ values ranging from -15 to 4°. The second ν${\mathit{i}}_{13/2}$ pair alignment occurs at a higher frequency (ħω≥0.45 MeV). Such theoretical results can explain nicely the double crossing observed in the yrast band of ${}_{}{}^{184}{}_{}{}^{}\mathrm{Pt}$ and the relevant blocking experiments in the neighboring odd-A nuclei. The result on ${}_{}{}^{186}{}_{}{}^{}\mathrm{Pt}$ is very different, as only the π${\mathit{h}}_{9/2}$ crossing is observed in the calculations up to a frequency of 0.40 MeV. This compares well with the data, which indicate one sharp band crossing in ${}_{}{}^{186}{}_{}{}^{}\mathrm{Pt}$ at low frequency.

The adequacy of using smoothly joined parabolic segments to parametrize the multihumped fission barriers has been tested by examining its simultaneous consistency with the three relevant fission observables, namely, the near-barrier fission cross sections, isomeric half-lives, and the ground-state spontaneous fission half-lives of a wide variety of a total of 25 actinide nuclides. The penetrabilities through such multihumped fission barriers have been calculated in the Wentzel-Kramers-Brillouin approximation, and the various fission half-lives have been determined using the formalism given earlier by Nix and Walker. The results of our systematic analysis of these actinide nuclides suggest that such a parametrization is quite adequate at least for the even-even nuclei, as it reproduces satisfactorily their various observed fission characteristics. Major difficulties remain, however, for the odd mass and for the doubly odd nuclei where the calculated ground-state spontaneous fission half-lives are found to be several orders of magnitude larger than those measured. Possible reasons for such discrepancies are discussed. Fission branching ratios of the decay of the shape isomers in various actinide nuclides have also been calculated and are compared with their measured values.

The multiphonon method previously developed for a system containing an even number of fermions is extended to the case where this number is odd. Recursion formulas well suited for realistic applications to odd-mass nuclei are given for overlaps and matrix elements of one- and two-body operators.

The isovector spin-flip M1 strength function in the deformed heavy nuclei ${}_{}{}^{156}{}_{}{}^{}\mathrm{Gd}$ and ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ is calculated in the quasiparticle random-phase approximation. Interaction parameters are adjusted to reproduce the energies of isobaric-analog and Gamow-Teller excitations observed in (p,n) charge-exchange reactions. A phenomenological spreading width for decay into background 2p2h states is introduced and adjusted to reproduce the M1 spin-flip strength function recently observed by elastic scattering of tagged photons on ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. With the model parameters fixed in this fashion, our calculations predict large quantities of spin-flip M1 strength (10–20 ${\mathrm{\mu }}_{\mathit{N}}^2$) between 5 and 10 MeV excitation in ${}_{}{}^{156}{}_{}{}^{}\mathrm{Gd}$ and ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$; it is strongly fragmented and should be observable by tagged-photon elastic scattering and proton inelastic scattering but probably not in high resolution inelastic electron scattering.

Charged particles and high energy γ rays from the decay of the ${}_{}{}^{156}{}_{}{}^{}\mathrm{Er}$ compound nucleus populated at ${\mathit{E}}_{\mathit{x}}$=47 MeV excitation energy by the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{144}$Sm and ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$${+}^{92}$Zr reactions have been measured to study possible nonstatistical or entrance channel effects. The experimental spectra and published evaporation residue and neutron data are compared with statistical model calculations. The comparison shows that the statistical model with standard parametrization of level density and yrast lines describes reasonably well the bulk of experimental observables but not the shape of neutron spectra if account is taken of the enhancement factor for E2 transitions. The discrepancies between experimental data and model calculations are discussed.

Delayed fission from the electron-capture decay of ${}_{}{}^{232}{}_{}{}^{}\mathrm{Am}$ was studied. The ${}_{}{}^{237}{}_{}{}^{}\mathrm{Np}$(α,9n${)}^{232}$Am reaction with multiple ${}_{}{}^{237}{}_{}{}^{}\mathrm{Np}$ targets was used to produce ${}_{}{}^{232}{}_{}{}^{}\mathrm{Am}$. The fission properties and half-life of ${}_{}{}^{232}{}_{}{}^{}\mathrm{Am}$ were measured using a rotating-wheel system. The half-life of ${}_{}{}^{232}{}_{}{}^{}\mathrm{Am}$ was found to be 1.31±0.04 min from measurements of the fission activity. A highly asymmetric mass-yield distribution was observed for the fission activity, and the average total kinetic energy of the fission fragments was found to be 174±5 MeV. Radiochemical separations confirmed the elemental assignment of the fissioning species to americium or fission following shortly after the decay of americium. The cross section for ${}_{}{}^{232}{}_{}{}^{}\mathrm{Am}$ produced by this reaction and decaying by electron capture was determined to be 1.3±0.2 μb by measuring the intensities of the daughter plutonium K x rays in radiochemically separated americium samples. The delayed-fission probability was found to be (6.9±1.0)×${10}^{\mathrm{-}4}$ from the measured ratio of fissions to plutonium K x rays. The observed fissions were unambiguously assigned to electron-capture-delayed fission of americium by measuring the time correlation between the plutonium K x rays resulting from americium K capture and the subsequent fission.

Secondary charge and mass distributions have been measured for projectilelike fragments (PLF’s) in strongly damped reactions of ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$${+}^{165}$Ho at 16 MeV per nucleon bombarding energy. Statistical model evaporation calculations were compared with these distributions and with neutron multiplicities and temperatures for PLF and targetlike fragments (TLF’s) to obtain the primary distributions prior to light-particle emission. The deduced primary distributions indicate a net transfer of protons to the target in contrast to the predictions of the nucleon transport exchange model, which predicts a net transfer of neutrons to the projectile. The results suggest an equal division of the available excitation energy at small total kinetic-energy (TKE) losses (up to 200 MeV) with thermal energy division occurring only at the largest TKE losses (≊325 MeV).

Particle emission following ${\mathrm{\pi }}^{+}$ absorption on ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ at ${\mathit{T}}_{\mathrm{\pi }}$=50, 100, 150, and 200 MeV was studied with a large-solid-angle detector. Evidence is found for a three-nucleon-absorption mode, which takes place predominantly on pnn triplets. This mode increases in importance from about a quarter of the absorption cross section at 50 MeV to about one-half at 200 MeV.

Very energetic light ions (primarily protons and alphas) with energies often approaching the full beam energy have been observed at or near θ=0° in heavy-ion collisions, Z=8 to 28, E/A=̇9 to 40 MeV/nucleon from Ta and, in selected cases, Cu targets. Analysis of spectral shapes and angular distributions using a standard moving source model requires that the source velocity approaches the beam velocity as θ→0° and that the spectral slope parameters and apparent source temperatures be increased. Large values for the latter (${\mathit{T}}_{\mathit{S}}$→16 MeV), which are typically twice as large as those deduced from complex fragment emission, are often required to fit the alpha particle spectra θ=0°. Massive cluster transfer and other quasitransfer mechanisms may provide an alternative model for the generation of the E→${\mathit{E}}_{\mathrm{beam}}$ alpha particles and other light fragments.

The elastic scattering of ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ on ${}_{}{}^{58,64}{}_{}{}^{}\mathrm{Ni}$ and fusion excitation functions for ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$${+}^{58,64}$Ni and ${}_{}{}^{34}{}_{}{}^{}\mathrm{S}$${+}^{64}$Ni have been measured at energies near the Coulomb barrier. Our results differ in several important respects from previous measurements on these systems. Coupled-channels calculations which explicitly allow for collective inelastic excitations and single-nucleon transfer reactions simultaneously reproduce the main features of the new elastic-scattering and fusion data.