The β decay of the neutron-rich nuclides, 40-s ${}_{}{}^{139}{}_{}{}^{}\mathrm{Xe}$, 1.7-s ${}_{}{}^{141}{}_{}{}^{}\mathrm{Xe}$, and 0.4-s ${}_{}{}^{143}{}_{}{}^{}\mathrm{Xe}$ to levels of odd-Z ${}_{}{}^{139}{}_{}{}^{}\mathrm{Cs}$, ${}_{}{}^{141}{}_{}{}^{}\mathrm{Cs}$, and ${}_{}{}^{143}{}_{}{}^{}\mathrm{Cs}$, respectively, has been studied using sources isolated from fission products by on-line mass separation. The data collected include gamma-ray and conversion electron singles spectra as well as gamma-ray coincidence and angular correlation spectra. New levels have been identified in ${}_{}{}^{139}{}_{}{}^{}\mathrm{Cs}$ including a doublet at 393 keV, and new spin and parity assignments are proposed. New data are presented for ${}_{}{}^{141}{}_{}{}^{}\mathrm{Cs}$ levels in support of an earlier proposed level scheme by Talbert and Cook. Evidence for a 0.4-s half-life for ${}_{}{}^{143}{}_{}{}^{}\mathrm{Xe}$ has been found, and a level at 90 keV is proposed for ${}_{}{}^{143}{}_{}{}^{}\mathrm{Cs}$. The resulting level structures for the neutron-rich Cs nuclides are compared with level structures of other odd-Z neutron-rich nuclides and neutron deficient Cs nuclides. The transition from the structure observed near the closed N=82 neutron shell to deformed structures described by Nilsson model orbitals is discussed.

The description of p-shell orbitals in the A=14 nuclear system in terms of relativistic wave functions, which are solutions to the Dirac equation with strong scalar and vector potentials, provides a good description of the M1 form factors in ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ and the greatly suppressed ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ beta decay rate.

The decays of three new neutron-rich nuclides ${}_{}{}^{111}{}_{}{}^{}\mathrm{Tc}$, ${}_{}{}^{113}{}_{}{}^{}\mathrm{Ru}$, and ${}_{}{}^{113}{}_{}{}^{}\mathrm{Rh}$ have been observed at an on-line isotope separator facility. In addition, the beta decays of several other n-rich isotopes with A>100 have been studied for the first time. The new half-lives reported in this work include: ${}_{}{}^{111}{}_{}{}^{}\mathrm{Tc}$ [$T_{1/2}$=0.30(3) s], ${}_{}{}^{111}{}_{}{}^{}\mathrm{Ru}$ [2.12(7) s], ${}_{}{}^{112}{}_{}{}^{}\mathrm{Ru}$ [1.75(7) s], ${}_{}{}^{113}{}_{}{}^{}\mathrm{Ru}$ [0.80(10) s], ${}_{}{}^{113}{}_{}{}^{}\mathrm{Rh}$ [2.72(22) s], and ${}_{}{}^{118}{}_{}{}^{}\mathrm{Pd}$ [2.24(17) s]. In general, these results support the microscopic theoretical half-life predictions below Z=50.

The energy spectra and wave functions of ${}_{}{}^{19}{}_{}{}^{}\mathrm{N}$ and ${}_{}{}^{19}{}_{}{}^{}\mathrm{O}$ are calculated using a modification of the Millener-Kurath interaction. The results are used to predict the half-life and decay modes of both the allowed and first-forbidden ${\beta }^{\mathrm{-}}$ decays of ${}_{}{}^{19}{}_{}{}^{}\mathrm{N}$. Comparison is made to recent experiments.

The existence of superdeformed shell closures together with pairing and the nuclear temperature effects are shown to explain the originally unexpected properties of the superdeformed band observed up to I∼60ħ in the ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$ nucleus. No parameters were adjusted to the superdeformed band properties. Population, and depopulation of the superdeformed bands, the moments of inertia, and side feeding properties are discussed and qualitatively understood. The use of the free-energy calculation results and the microcanonical ensemble formulation of the level-density problem at high-spin are proposed and discussed.

Employing a pairing-plus-quadrupole model interaction Hamiltonian, especially suited for the Os-Pt region, the ground-state structure of these nuclei for A=186 to 192 is investigated following a self-consistent Hartree-Fock-Bogoliubov approach. Effects of the inclusion of the hexadecapole degrees of freedom in the Hamiltonian are also studied. All the isotopes of osmium considered here come out to be prolate (asymmetry parameter, γ=0) in shape in the ground state with flat potential-energy surfaces in the γ direction unless the hexadecapole degrees of freedom are included. ${}_{}{}^{186}{}_{}{}^{}$,188Pt are triaxial with γ≃12°, and ${}_{}{}^{190}{}_{}{}^{}\mathrm{Pt}$ and ${}_{}{}^{192}{}_{}{}^{}\mathrm{Pt}$ may be considered as oblate with γ≃33° and 44°, respectively. Inclusion of the hexadecapole force does not have much effect on the equilibrium values of shape parameters of Pt isotopes.

The energy levels of g.s. bands, β bands, and γ bands of ${}_{}{}^{154\mathrm{-}162}{}_{}{}^{}\mathrm{Dy}$ isotopes are studied in the model of the traditional interacting boson approximation, allowing one boson to break and form a quasiparticle pair. The two quasiparticles are allowed to excite to the $i_{13/2}$ and $h_{11/2}$ orbitals. It was found that the energy levels of the g.s., β, and γ bands of even-even Dy nuclei can be reproduced very well. The backbends of the moment of inertia can also be reasonably described. The yrast B(E2) values are also calculated and compared with the experimental data.

In analogy with a symmetry-restoring treatment of rotational invariance for deformed Hamiltonians, we discuss the case of a separable monopole pairing Hamiltonian in the quasiparticle basis. The results are compared to estimates of a conventional treatment based on the quasiparticle random phase approximation.

The SU(3) dynamical symmetries of the vibron and the nuclear vibron models have been applied to the ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ nuclei, respectively. Well established cluster bands with core-plus-alpha-particle structure and high-lying states populated as resonances in alpha scattering have been considered. Many resonances fit to the classification schemes of the energy spectra which have parameters largely determined by the well-known cluster bands. A procedure is proposed to take the Pauli principle into account, at an approximate level, when these models are applied to nuclei.

The finite-temperature Hartree-Fock-Bogoliubov cranking equation is solved for ${}_{}{}^{166}{}_{}{}^{}\mathrm{Er}$ for temperatures up to 2.8 MeV and spins up to 60ħ. The deformation, pair gaps, moment-of-inertia, and level density parameter are determined as functions of the temperature and the angular momentum. For a fixed spin, increasing the temperature induces a transition from a prolate shape to an oblate shape, and a transition from collective rotation to noncollective rotation. The spin dependence of the critical temperature is determined.

In even-even Zr nuclei, with the neutron number increasing from N=56 on, a steady lowering of the first excited $0^{+}$ state is observed. This excited $0^{+}$ state has been mainly related to the proton excitation across the Z=40 subshell. Starting from the shell-model matrix element, connecting the (2$p_{1/2}$${)}^2$$0^{+}$ and (1$g_{9/2}$${)}^2$$0^{+}$ configurations in ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, we point out that a large reduction in the coupling matrix element is needed to explain the very low $0^{+}$ excitation energy at N=58, N=60. This reduction is calculated, starting from the matrix element connecting the spherical valence neutron configuration and a Nilsson model deformed wave function describing the neutron component.

The low-spin states and intermediately high spin states below the second backbendings of N=88 isotones were studied in the interacting-boson-plus-one-fermion-pair model. It was found that the energy spectra can be reproduced quite well. The spectroscopic quadrupole moments of ${}_{}{}^{154}{}_{}{}^{}\mathrm{Dy}$ were calculated and compared with the available experimental data. Both the backbending behavior and the decrease of the quadrupole moments at high spin states can be reproduced.

The trinucleon asymptotic normalization constants are calculated from solutions to the momentum space Faddeev equations using the new static Bonn two-nucleon potential. We find ‖$C_0$${\Vert }^2$=3.39, $C_2$/$C_0$=0.043 ${(}^3$H), and $D_2$=-0.22 ${\mathrm{fm}}^2$. These values are in agreement with most of the experimental data. Furthermore, our results support the capability of the static Bonn potential to predict low-energy three-nucleon observables reasonably well without the introduction of a three-body force.

Bipolar harmonics are bilinear products of spherical harmonics with different arguments coupled to total angular momentum L; they are frequently used in nuclear physics. We present analytic mappings of these harmonics for L≤3 onto an irreducible basis, as well as a discussion of their properties. Mappings of lower order have proven very useful recently in treating deuteron photo- disintegration and in solving the Faddeev equations for the triton.

The nuclear response function in the random-phase-approximation theory may be substantially altered at high excitation energy due to coupling of 1p-1h to 2p-2h or higher excitations. In the continuum region of quasi-elastic scattering, this coupling can be included by inserting into the random-phase-approximation Green’s function a complex self-energy for the p-h states, which depends only on their energy, spin (S), and isospin (T). This allows the full response to be expressed directly as an integral over the random-phase-approximation response. The self-energies, which can be determined from empirical single-particle spreading widths, are large in the spin and isospin channels, but small in the T,S=0,0 channel, giving rise to substantial damping in all channels except 0,0. We apply this method to calculate damping of the random-phase-approximation surface response, and discuss the consequences for cross sections and spin observables in quasi-elastic (p,p’) and (n,p) reactions.

We develop a random-phase approximation theory of the spin-isospin nuclear surface response, suitable for the interpretation of recent experiments of polarized (p,p’) and charge exchange ${(}^3$He,t) reactions. The present approach extends our previous treatment of the volume responses, which was quite successful in accounting for inelastic electron scattering data. Its crucial ingredient is a vertex function which localizes the probe-target interaction on the surface region of the nucleus. Our results compare rather successfully with both the (p,p’) and ${(}^3$He,t) experiments, although some difficulties remain to be overcome. Indeed, we predict a ratio between the spin-longitudinal and the spin-transverse nuclear responses still somewhat larger than the measured value. Concerning the charge-exchange ${(}^3$He,t) reaction, we qualitatively account for the progressive softening of the peak of the cross section at large momentum transfer, thus confirming the role of the pion in nuclear structure. We tentatively ascribe the remaining discrepancies with the ${(}^3$He,t) data to relativistic kinematics effects.

We derive the long- range behavior of an effective interaction for a system with three identical particles. We start our derivation from the zero range theory in configuration space and we show that the asymptotic effective potential, in the relative distance of the subsystem to the third particle, goes as -exp(-λr)/($r^{3/2}$).

Semicentral Ar+KCl, La+La, and Ar+Pb collisions at 800 MeV/nucleon were studied using a streamer chamber. The results are analyzed in the framework of the transverse momentum analysis and in terms of the average sphericity matrix. A critical examination of the analysis procedures, both experimental and theoretical, is given. New procedures are described to account for overall momentum conservation in the reaction, and to correct for azimuthal variations in the detection efficiency. Average transverse momenta per nucleon in the reaction plane are presented for deuterons emitted in the forward hemisphere, as these provide the most reliable information. A Vlasov-Uehling-Uhlenbeck calculation with a stiff equation of state gives a good fit to the momenta in the Ar+Pb reaction. Flow effects parametrized further using the sphericity tensor are found stronger than in the cascade model and consistently weaker than predicted by hydrodynamics. Parameters from the sphericity tensor exhibit a larger variation as a function of multiplicity than do the average momenta per nucleon.

The associated phenomena of preequilibrium emission and incomplete fusion in heavy ion collisions at low impact parameter are studied in the context of inverse kinematics and of a symmetrical system. The ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$${+}^{13}$C, ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, and ${}_{}{}^{45}{}_{}{}^{}\mathrm{Sc}$ reactions performed at ${\mathit{E}}_{\mathrm{?}}$ MeV/nucleon are discussed. Heavy fragments and light particles have been detected inclusively and exclusively. Salient features of preequilibrium and incomplete fusion are presented and discussed in the framework of theoretical models. Characteristics of nuclear species formed in incomplete fusion are studied and possible limits to fusion are examined. Various possible origins of preequilibrium emission are suggested. The ${}_{}{}^{40}{}_{}{}^{}$Ar${+}^{13}$C reaction appears to be a particular case as concerns the preequilibrium emission.

Angular correlations between light particles have been studied to probe the extent to which a thermally equilibrated system is formed in heavy ion collisions near the Fermi energy. Single-light-particle inclusive energy spectra and two-particle large-angle correlations were measured for 40 and 50 MeV/nucleon C+C, Ag, and Au. The single-particle inclusive energy spectra are well fit by a three moving source parametrization. Two-particle large-angle correlations are shown to be consistent with emission from a thermally equilibrated source when the effects of momentum conservation are considered. Single-particle inclusive spectra and light-particle correlations at small relative momentum were measured for 35 MeV/nucleon N+Ag. Source radii were extracted from the two-particle correlation functions and were found to be consistent with previous measurements using two-particle correlations and the coalescence model. The temperature of the emitting source was extracted from the relative populations of states using the quantum statistical model and was found to be ${4.8}_{\mathrm{-}2.4}^{+2.8\mathrm{}}$ MeV, compared to the 14 MeV temperature extracted from the slopes of the kinetic energy spectra.