The distribution of rotational energy spacings for low-spin yrast states in over two thousand pairs of deformed rare-earth even-even nuclei are studied to determine key factors that correlate with the moments of inertia. Nuclei with near identical P values (P=${\mathit{N}}_{\mathit{pN}\mathit{n}}$/[${\mathit{N}}_{\mathit{p}}$+${\mathit{N}}_{\mathit{n}}$] where ${\mathit{N}}_{\mathit{p}}$ and ${\mathit{N}}_{\mathit{n}}$ are the numbers of valence protons and valence neutrons) are more than an order of magnitude more likely to show near identical bands than nuclei with different P values. This is, by far, the highest correlation found: no other variable is even 20% as effective. The statistical significance of these large P enhancements and the special relation between P and ground-state mean-field structures is confirmed by a complementary analysis of negative parity near identical bands, which show no P enhancement at all.

It is shown that the ΔI=2 staggering effect recently discovered in superdeformed rotational bands could be explained by a phenomenological theory of ${\mathit{C}}_{4\mathit{v}}$ bifurcation. In this scenario, the energy staggering is associated with the alignment of the total nuclear angular momentum along the axis perpendicular to the long deformation axis of the prolate nucleus.

We report ${}_{}{}^3{}_{}{}^{}\mathrm{H}$ binding energy calculations using inversion potentials generated from phase shifts corresponding to contemporary nucleon-nucleon potentials as well as modern phase shift analyses. We place limits upon the calculated triton binding energy based on a local potential due to the underlying uncertainties in the potential model generated directly from the nucleon-nucleon phase shifts. We explore the role of the nonlocality of momentum-dependent potentials in the triton binding energy. In particular, we find the additional binding energy in the case of the Bonn-B potential is due to a long range nonlocality.

The γ-ray transitions following the β decay of ${}_{}{}^{110}{}_{}{}^{}\mathrm{In}_{}^{\mathit{m}}{}_{}{}^{}$ (half-life 69 min) were observed using Compton-suppressed Ge detectors. The activity was produced by the ${}_{}{}^{111}{}_{}{}^{}\mathrm{Cd}$(p,2n) reaction at a bombarding energy of 18.9 MeV. Singles in multispectra mode and γγ-coincidence experiments were performed. Approximately 150 transitions were assigned to ${}_{}{}^{110}{}_{}{}^{}\mathrm{Cd}$, based on their measured half life and/or observation in coincidence with well-known lines. The ${\log }_{10}$(ft) values of nearly all observed levels were determined and an analysis of the beta-decay strength using microscopic theory was performed. The experimental data were interpreted in the framework of the interacting boson model.

The lifetimes of states in two of the ΔI=1 bands in ${}_{}{}^{196}{}_{}{}^{}\mathrm{Pb}$ have been measured using the Doppler shift attenuation method, and a new ΔI=1 band has been observed in this nucleus. States in the bands were populated in the reaction ${}_{}{}^{107}{}_{}{}^{}\mathrm{Er}$${(}^{30}$Si,4n) at a beam energy of 142 MeV. Individual level lifetimes were extracted from the data by a analysis of the Doppler broadened γ-ray lineshapes. Under the assumption of pure M1 radiation, average reduced transition strengths B(M1)∼1.5 W.u. were obtained. The B(M1) values in both the ‘‘regular’’ and ‘‘irregular’’ bands exhibit similar dependence on spin. The neutron and proton configurations and nature of the collectivity in these bands is discussed.

A systematic study of the α decay of ${}_{}{}^{181\mathrm{-}186}{}_{}{}^{}\mathrm{Au}$ utilizing an on-line isotope separator has revealed several α groups and resulted in the observation of the α decay of ${}_{}{}^{186}{}_{}{}^{}\mathrm{Au}$ and ${}_{}{}^{185}{}_{}{}^{}\mathrm{Pt}$. By simultaneous measurement of γ-ray and x-ray spectra and use of known EC/${\mathrm{\beta }}^{+}$ decay schemes, α-decay branching ratios and hindrance factors were deduced for each α transition. In ${}_{}{}^{185}{}_{}{}^{}\mathrm{Au}$ and ${}_{}{}^{183}{}_{}{}^{}\mathrm{Au}$ the ground state is known to be dominated by the 5/$2^{\mathrm{-}}$,1/2[541] configuration associated with the ${\mathit{h}}_{9/2}$ intruder from above the Z=82 closed shell. Thus, the unhindered α decay of these parents identify levels in the Ir daughters which also are dominated by the ${\mathit{h}}_{9/2}$ orbital. Several previously unknown low-lying γ-ray transitions were observed in the Ir daughters by means of α-γ coincidence measurements. The hindrance factor for the α decay of ${}_{}{}^{181}{}_{}{}^{}\mathrm{Au}$ to the 5/$2^{\mathrm{-}}$,1/2[541] ground state of ${}_{}{}^{177}{}_{}{}^{}\mathrm{Ir}$ suggests that the ground state of ${}_{}{}^{181}{}_{}{}^{}\mathrm{Au}$ has a different configuration than those of ${}_{}{}^{183}{}_{}{}^{}\mathrm{Au}$ and ${}_{}{}^{185}{}_{}{}^{}\mathrm{Au}$.

The negative parity state of ${}_{}{}^{172\mathrm{-}180}{}_{}{}^{}\mathrm{Os}$ are studied in the framework of the interacting boson approximation model. The negative parity states are formed by including one f boson or allowing one boson to break into two fermions which are placed in orbits with opposite parity. The calculated level energies and B(E2)’s are in reasonable agreements with experiments. From the comparison of intrinsic structure it suggests that the relative energy of the quasiparticles may be the most important factor in the calculations.

The γ- or quasi-γ-band energy staggering in low-spin, low-energy spectra of even-even nuclei is discussed. The staggering indices of γ-soft and triaxial nuclei are calculated in the interacting boson model O(6) limit with three-body potential and general axially asymmetric rotor model with β vibration, respectively. It is found that these staggering indices have opposite signs and provide clear distinctions between γ-soft and triaxial shapes. The experimental data of energy spectra of 140 of even-even nuclei in the mass region A=64 to 200 are compared to the predictions for broken O(6) symmetry with varying strength of the three-body interaction, and for the axially asymmetric rotor model with varying γ dependence. The results show that most nuclei with clear staggering are γ soft or γ unstable, but a few may be slightly triaxial, and that almost all the axial nuclei are slightly γ soft, some of them exhibiting shape transitions from axial to γ-soft to triaxial shape with increasing angular momentum.

The properties of the boson-pairing operator of the O(6) limit of the interacting boson model are being investigated. The pairing operator acting on an O(6) eigenstate produces an eigenstate with the same seniority σ, but with two more bosons, i.e., a state in a different nucleus. States generated by the successive application of the pairing operator constitute an O(6) pairing multiplet. Properties of the multiplets and the comparison with experiment are being discussed

Alpha-chain states in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ are studied by employing the isomorphic shell model. Where possible α particles and their spatial distribution are derived, instead of being assumed as usual in α-cluster models. It has been found that the average forms of both the ground state and the first $0^{+}$ excited state can be associated with an α chain composed of three α particles in a row. The ground state and the first $0^{+}$ excited state energies and their rotational bands, together with their charge radii and intrinsic quadrupole moments, have been computed and compared with the predictions of α-particle models. With reference to experimental data, all quantities examined lend support to the present approach.

We consider negative parity excitations in ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, ${}_{}{}^{\mathrm{\pi }}{}_{}{}^{}$=$0^{\mathrm{-}}$, $1^{\mathrm{-}}$, and $2^{\mathrm{-}}$ with isospin T=0 and 1. In a one-particle one-hole calculation the unnatural parity states, J=$0^{\mathrm{-}}$ and $2^{\mathrm{-}}$ come down in energy linearly with the increasing strength of the tensor interaction, ultimately coming below the original J=$0^{+}$ ground state. However in a shell model diagonalization in a sufficiently large space, although the states may start to come down, there is a turnaround so that the excitation energies of these states thereafter increases with increasing tensor strength, and there is no energy inversion with the J=$0^{+}$ state.

The recoil catcher technique and gamma spectrometric assay of fission products were used to measure angular distribution of 17 fission products in ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ induced fission of ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$ at near barrier energies. The observed mass dependence of anisotropies of fission products in these systems are very different from that of p and α induced fission of ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$ at similar excitation energies. It has been suggested that the difference in the rotational energy for the symmetric and asymmetric modes for large compound nucleus spins could be responsible for the observed variation. No systematic change in the mass dependence of anisotropies across the Bussinaro-Gallone point was observed. For ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ induced fission of ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$, sharp variation in anisotropies have been observed in the mass region 120–135. This has been attributed to transfer induced fission.

Coincident protons and neutrons from the reaction γ→d→pn${\mathrm{\pi }}^0$ were measured at a photon energy of 290 MeV. Cross sections and beam asymmetries were extracted for nucleon momenta above the quasifree region for the first time. The measured cross sections are compared with the results of a cascade Monte Carlo calculation.

It is demonstrated that the partition of excitation energy between receptor and donor, in quasielastic heavy-ion transfer reactions, at near barrier energies can be studied by γ-ray spectroscopy. Reactions between ${}_{}{}^{161}{}_{}{}^{}\mathrm{Dy}$ and ${}_{}{}^{58,61}{}_{}{}^{}\mathrm{Ni}$ at bombarding energies 265 and 270 MeV respectively have been studied using the particle-γ coincidence technique. From the observed deexcitation γ rays originating in Ni, we derived the average excitation energy carried by the receptor to be ∼0.8 MeV (${\mathit{Q}}_{\mathit{g}\mathit{g}}$=2.5 MeV) for ${}_{}{}^{59}{}_{}{}^{}\mathrm{Ni}$ and ∼2.5 MeV (${\mathit{Q}}_{\mathit{g}\mathit{g}}$=4.1 MeV) for ${}_{}{}^{62}{}_{}{}^{}\mathrm{Ni}$ in the one-neutron transfer reaction channel. A broad bump peaking about 1 MeV attributed to intrinsic excitation was observed in ${}_{}{}^{160}{}_{}{}^{}\mathrm{Dy}$ for the ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ beam and about 1–2 MeV for the ${}_{}{}^{61}{}_{}{}^{}\mathrm{Ni}$ beam. Distorted-wave Born approximation analysis reproduces the general features of the excitation-energy partition between the receptor and donor although discrepancies exist when comparing populations of individual final states.

A radioactive nuclear beam of 10.2 MeV ${}_{}{}^6{}_{}{}^{}\mathrm{He}$, with typical intensity 5×${10}^4$ ${\mathrm{s}}^{\mathrm{-}1}$, was produced via the ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$${(}^7$Li${,}^6$He${)}^{10}$B reaction and elastically scattered from targets of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{Ni}$, and ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$. Scattering from C and Ni was observed through sufficiently large angles (up to 60° c.m. and 85° c.m., respectively) to show large deviations from Rutherford scattering. The Au target gave, as expected, pure Rutherford scattering. Optical potential previously used for low-energy ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ and ${}_{}{}^8{}_{}{}^{}\mathrm{Li}$ ions generally accounted for the shapes of the angular distributions but, for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, predict oscillations not present in the ${}_{}{}^6{}_{}{}^{}\mathrm{He}$ data. ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ optical potentials predict much smaller deviations from Rutherford scattering than those observed.

This work studies the effect of a high-density correction to the Boltzmann-Uehling-Uhlenbeck (BUU) dynamics, i.e., the inclusion of triple scattering in heavy-ion reactions at intermediate incident energies. By using both schematic model calculations and the modified BUU simulations with triple scatterings incorporated, it has been suggested that the inclusion of triple scattering into the reaction dynamics could lead to an enhancement of the high-energy component in the nucleon distribution at an early stage of the reaction. An interesting point of this study is to indicate that this enhancement has been retarded considerably by the Fermi motion and mean field. Thus, as far as this effect is considered, the incorporation of triple scattering is not sufficient to account for the difference between the conventional BUU predicted and measured subthreshold particle production data, such as pions. Our results also show that these conclusions do not rely on the approximations adopted in the existing treatments of triple scatterings.

We present a method for macroscopic quantum tunneling, named dynamical norm method, which works over a very wide range of situations between the adiabatic and the sudden limits. We examine the validity of the method by studying the effects of linear oscillator coupling on the tunneling rate through an Eckart barrier. We then apply the method to discussing the effects of a nuclear intrinsic excitation on fission. This method shows that the adiabaticity of the tunneling process is governed not only by the relative time scale of the tunneling degree of freedom and of environmental degrees of freedom, but also by the properties of the coupling between them. We also show that the dynamical norm factor which represents nonadiabatic effects in our method is closely related to the dissipation factor in the Caldeira-Leggett theory for dissipative quantum tunneling.

The Vlasov-Nordheim equation is solved numerically on a lattice for nuclear matter in two dimensions. We discuss the reliability of the model at normal density and then study the response of the system to small perturbations. We find deterministic chaos inside the spinodal zone where fragment formation occurs. We discuss in detail the dynamical features of this phenomenon in order to clarify the mechanisms leading to nuclear disassembly in heavy-ion collisions.

We present first- and second-order corrections to the eikonal phase shifts for heavy-ion elastic scattering based on Coulomb trajectories of colliding nuclei. Including the first- and second-order corrections improves the agreement with the experimental data and the optical model result for the elastic scatterings in the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ systems at ${\mathit{E}}_{\mathrm{lab}}$=1503 MeV.

The effect of including mass-asymmetry dependent fission delay times into the statistical model has been investigated. The shape of the predicted charge distribution of fission fragments is found to be very sensitive to the magnitude and mass-asymmetry dependence of these delay times. Measured mass-asymmetry dependent prefission neutron multiplicities were fit with calculated presaddle values by varying the fission delay times. The resultant predictions for the charge distributions are found to have shapes inconsistent with those measured for similar mass systems indicating that measured prefission multiplicities cannot be accounted for by presaddle emission alone. Limitations to the magnitude of the presaddle component are discussed.