Level spins and transition energies of 26 superdeformed bands in the A∼190 region are studied with the rotational spectral formula derived from the cranking Bohr-Mottelson Hamiltonian proposed by us with satisfactory results.

An extended version of the standard pion-nucleus optical potential is presented using the momentum-space formulation of the multiple scattering theory. This potential is used for studying the influence of nonlocal effects and nuclear structure on the characteristics of light pionic atoms. A method is suggested to treat the long-range two-nucleon correlations involved in the second order optical potential. Particularly, the spin-orbital Fermi motion correction to the first-order optical potential, the center-of-mass correlations, and the spin-isospin corrections to the second-order optical potential are discussed in some detail. The results are presented in comparison with the experimental data for the 1s and 2p levels of light pionic atoms up to ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ca}$.

Within the one level R-matrix approach, expressions are derived for the hindrance factors of cluster radioactive decays in which y the shell model with effective residual interactions [e.g.,thelar in the Michigan State University version for nearly spherical nuclei, or the enlarged superfluid model (ESM) recently proposed for deformed nuclei]. The exterior wave functions are calculated from a cluster-nucleus double-folding model potential obtained with the M3Y interaction. As examples of the cluster decay fine structure we analyzed the particular cases of α decay of ${}_{}{}^{241}{}_{}{}^{}\mathrm{Am}$ and ${}_{}{}^{243}{}_{}{}^{}\mathrm{Cm}$, ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ decay of ${}_{}{}^{223}{}_{}{}^{}\mathrm{Ra}$, and ${}_{}{}^{34}{}_{}{}^{}\mathrm{Si}$ decay of ${}_{}{}^{243}{}_{}{}^{}\mathrm{Cm}$. Good agreement with the experimental data is obtained.

The rotation of hot triaxial nuclei is studied with the ${\mathit{i}}_{13/2}$ model. A single j=13/2 shell in the presence of a triaxial quadrupole potential is rotated in three dimensions and at finite-temperature to calculate statistical fluctuations in the orientation of the intrinsic nuclear shape relative to the rotation axis. Calculations are performed with the cranking model under two alternative constraints: (i) the rotational frequency is held constant as the rotation axis is varied, and (ii) the average spin is held constant as the rotation axis is varied. The thermal dependence of the orientation probability distribution is studied for each constraint. The existence of ‘‘tilted’’ yrast state solutions is demonstrated at zero-temperature for even particle number. These solutions correspond to stable uniform rotation about an axis that lies in a principal plane of the quadrupole potential. The possibility of observing stable tilted solutions in the extended Landau theory of hot rotating nuclei is discussed.

We discuss various relativistic models describing ground-state properties of spherical nuclei. Relativistic mean-field and Hartree-Fock theories, which serve as a starting point for subsequent models, are reviewed. Using a density-dependent parametrization of the Dirac-Brueckner G matrix in nuclear matter, we achieve an effective Dirac-Brueckner-Hartree-Fock model for finite nuclei. Finite nuclei results obtained with this model are compared with the less advanced density-dependent mean-field model, which simulates Dirac-Brueckner calculations for nuclear matter as well. It is shown that the effective Dirac-Brueckner-Hartree-Fock approach most successfully reproduces experimental data concerning spherical nuclei.

Multifragment emission data from the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$+Ag reaction are examined in the context of an intranuclear cascade code followed by an expanding, emitting source calculation. The role of Δ resonances in the energy dissipation process is stressed. In addition, the importance of employing a distribution of excitation energies in such analyses is pointed out. In order to describe the data within the context of this hybrid model, excitation via Δ resonance formation and expansion of the emitting source are required.

Excitation functions were measured for the ${}_{}{}^{63}{}_{}{}^{}\mathrm{Cu}$(n,α${)}^{60}$${\mathrm{Co}}^{\mathit{m}}$, ${}_{}{}^{65}{}_{}{}^{}\mathrm{Cu}$(n,α${)}^{62}$${\mathrm{Co}}^{\mathit{m}}$, and ${}_{}{}^{65}{}_{}{}^{}\mathrm{Cu}$(n,α${)}^{62}$${\mathrm{Co}}^{\mathit{g}}$ reactions over the neutron energy range of 6.3 to 14.8 MeV. Use was made of the activation technique in combination with high resolution γ-ray spectroscopy. The nuetrons were produced via the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(d,n${)}^3$He reaction using a deuterium gas target at a variable energy compact cyclotron (${\mathit{E}}_{\mathit{n}}$=6.3–11.9 MeV) and via the ${}_{}{}^3{}_{}{}^{}\mathrm{H}$(d,n${)}^4$He reaction using a solid Ti-T target at a neutron generator (${\mathit{E}}_{\mathit{n}}$=13.7–14.8 MeV). From the available experimental data isomeric cross section ratios were determined for the isomeric pair ${}_{}{}^{60}{}_{}{}^{}\mathrm{Co}_{}^{\mathit{m},}{}_{}{}^{}$g in ${}_{}{}^{63}{}_{}{}^{}\mathrm{Cu}$(n,α) and ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$(n,p) reactions, and for the pair ${}_{}{}^{62}{}_{}{}^{}\mathrm{Co}_{}^{\mathit{m},}{}_{}{}^{}$g in the ${}_{}{}^{65}{}_{}{}^{}\mathrm{Cu}$(n,α) reaction. Statistical model calculations taking into account precompound effects were performed for the formation of both the isomeric and ground states of the products. The calculational results on the total (n,p) and (n,α) cross sections agree well with the experimental data; in the case of isomeric states, however, some deviations occur. The experimental isomeric cross section ratios are reproduced only approximately by the calculation; at 15 MeV the spin distribution of the level density has a significant effect on the calculation. For low-lying levels the isomeric cross section ratio depends strongly on the spins of the levels involved and not on their excitation energies. At a given neutron energy the population of the higher spin isomer appears to be higher in the (n,α) process than in the (n,p) reaction.

The ${}_{}{}^4{}_{}{}^{}\mathrm{He}$${(}^4$He${,}^3$He${)}^5$He(g.s.) reaction was observed at 118 MeV for c.m. angles from about 30° to 120°. DWBA calculations accurately predict the shapes of the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ spectra for ${\mathrm{\epsilon }}_{\mathrm{\alpha }\mathit{n}}$≤2.5 MeV, where ${\mathrm{\epsilon }}_{\mathrm{\alpha }\mathit{n}}$ is the relative energy of the final α-n system. However the measured differential cross sections are smaller than the DWBA predictions by about a factor of 2 at forward angles, and have a less pronounced minimum at 90° c.m. than the theory predicts.

The quasielastic scattering of the exotic neutron-drip-line nucleus ${}_{}{}^{14}{}_{}{}^{}\mathrm{Be}$ on a ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ target has been studied at an incident energy of 796 MeV, and compared with that of the ${}_{}{}^{12}{}_{}{}^{}\mathrm{Be}$ ‘‘core’’ at the same energy per nucleon. Evidence is presented that the phenomenological optical-model potential for the former system requires an attractive real surface term, as well as the ‘‘expected’’ surface imaginary term, in order to reproduce the experimental angular distribution.

The differential cross sections for the reactions ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ (γ,${\mathit{p}}_0$) and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ (γ,${\mathit{p}}_1$) have been measured in the energy range 21–26 MeV. Analysis of the present data and the ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ (γ,p) cross section reveals decay of the giant dipole resonance at 23 MeV, via the ${\mathit{p}}_4$ channel. The valence neutron does not appear to interact strongly with the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ core. Isospin splitting effects are observed.

We have performed a search for resonant states in low energy ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{-}}$ scattering through their decay to multiphoton final states using ${\mathit{e}}^{+}$ from ${}_{}{}^{68}{}_{}{}^{}\mathrm{Ga}$ sources and a Pb absorber. We obtained energy-sum and invariant mass spectra of coincident 2γ and 3γ events using the 20-element High Energy-Resolution Array (HERA) facility. No evidence for resonant states was found, and upper limits for the partial decay widths of such resonances were established in the energy range from 1.1 to 1.8 MeV.

The ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$(d${,}^3$He${)}^{28}$Al reaction has been investigated at 29 MeV incident energy. Observations using a split-pole magnetic spectrograph have been made of 55 levels of ${}_{}{}^{28}{}_{}{}^{}\mathrm{Al}$ in the range of excitation energy between 0 and 6.7 MeV. Most of them have been identified with ${}_{}{}^{28}{}_{}{}^{}\mathrm{Al}$ levels which have been previously observed by other techniques. The spectroscopic factors have been obtained for 23 of these levels through distorted-wave Born approximation analyses of measured angular distributions. The levels at ${\mathit{E}}_{\mathit{x}}$=3.105 and 3.762 MeV have been definitely assigned ${\mathit{J}}^{\mathrm{\pi }}$=$1^{+}$ and $0^{+}$, respectively. Four levels which are populated through the pickup of a ${\mathit{l}}_{\mathit{p}}$=1 proton have been observed at ${\mathit{E}}_{\mathit{x}}$=4.998, 5.406, 6.021, and 6.652 MeV. The excitation energies and spectroscopic factors for positive-parity states were compared with the results of a recent, complete sd-shell space, shell-model calculation. This comparison led to the identification of 21 shell-model levels with experimental levels. This comparison seems accurate enough to make very likely the ${\mathit{J}}^{\mathrm{\pi }}$=$3^{+}$ assignment for the levels at ${\mathit{E}}_{\mathit{x}}$=2.988 and 4.597 MeV which were previously assigned ${\mathit{J}}^{\mathrm{\pi }}$=(1,3${)}^{+}$.

Light charged particles from the reaction 640 MeV ${}_{}{}^{86}{}_{}{}^{}\mathrm{Kr}$${+}^{63}$Cu have been measured in singles and in coincidence with intermediate mass fragments, fissionlike fragments, and other light charged particles. Multiplicities for ${}_{}{}^1{}_{}{}^{}\mathrm{H}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ in association with the evaporation residues, fragments, and intermediate mass fragments have been determined. Composite nuclei, most of which decay to evaporation residues, are the major sources of evaporative light-charged particle emission. Average multiplicities for prescission ${}_{}{}^1{}_{}{}^{}\mathrm{H}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ can be associated with the composite nucleus en route to scission; they are relatively large and thus suggest a time scale for fission longer than that for evaporation. The multiplicities for ${}_{}{}^1{}_{}{}^{}\mathrm{H}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ in association with the intermediate mass fragments indicate that these fragments are usually born with a significant quantity of excitation energy. These multiplicities are used to estimate the primary masses and kinetic energies of the intermediate mass fragments.

Experimental results are compared for the two matched heavy ion reactions 337 MeV ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$${+}^{\mathrm{nat}}$Ag and 640 MeV ${}_{}{}^{86}{}_{}{}^{}\mathrm{Kr}$${+}^{63}$Cu as a test of the extent of equilibration of the intermediate composite nucleus ${}_{}{}^{149}{}_{}{}^{}\mathrm{Tb}_{}^{\mathrm{*}}{}_{}{}^{}$(${\mathit{E}}^{\mathrm{*}}$=194 MeV). Spin zones associated with the evaporation residues (ER) are found to agree well for these entrance channels. Agreement is not as close for the fission class due to the inclusion of deeply inelastic reactions (DIR) along with fusion-fission (FF) for the ${}_{}{}^{86}{}_{}{}^{}\mathrm{Kr}$ reaction. Inclusive and coincidence measurements of energy spectra and angular distributions for the light charged particles indicate that these reactions produce composite nuclei with similar temperatures, spins, and moments of inertia. The energy spectra for both reactions are identically shifted relative to statistical model calculations. This suggests that the composite nuclei are highly distended prior to their cooling by particle evaporation. Multiplicities also agree for ${}_{}{}^1{}_{}{}^{}\mathrm{H}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ production in association with the ER and FF reaction classes. It is noteworthy that prescission ${}_{}{}^1{}_{}{}^{}\mathrm{H}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ multiplicities are in such good agreement, because the magnitude of these multiplicities seems to be dictated by the dynamical time scale of the fission process. That these prescission multiplicities are large suggests that the fission time scale is slow relative to particle evaporation; that they match for these reactions indicates that this is an equilibrium property of the intermediate composite nuclei. We conclude that extensive and rapid thermalization and shape equilibration have occurred despite estimates that the nuclear relaxation time and decay lifetime are nearly the same.

Intermediate mass fragments have been studied from the reaction ${}_{}{}^{86}{}_{}{}^{}\mathrm{Kr}$${+}^{63}$Cu for ${}_{}{}^{86}{}_{}{}^{}\mathrm{Kr}$ beam energies of 486, 550, 640, and 730 MeV. Average center-of-mass (c.m.) energies are nearly constant with the c.m. angle and vary little with incident energy. Furthermore, the angular distributions are well approximated by 1/sin${\mathrm{\theta }}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$. From this and other evidence we conclude that equilibration has occurred prior to fissionlike asymmetric binary breakup of the composite nucleus in the predominant mechanism for IMF production.

The density distribution of ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ was obtained by assuming it to consist of a ${}_{}{}^9{}_{}{}^{}\mathrm{Li}$ core in a harmonic oscillator potential plus two neutrons. The density distributions of the two neutrons were expanded in Fourier-Bessel terms. The coefficients of the Fourier-Bessel expansions were obtained by calculating reaction cross sections in a Glauber-type model and comparing with experimental values. The halo structure of the nucleus is clearly manifested in the calculations. The density obtained was then used to calculate the real part of the proton-nucleus optical potential in the folding model. Good fits to the p${+}^9$Li and p${+}^{11}$Li elastic scattering data were obtained.

Optical model calculations for intermediate energy alpha particles are performed with single-folded potentials using a Woods-Saxon parametrization for the matter densities and Gaussians for the effective alpha-nucleon interaction. A nearside and farside decomposition of the angular distributions are performed. We show that the refraction determines the gross features of the angular distributions.

The nonlocal Schrödinger equation is solved rigorously in a microscopic folding model, incorporating both direct and knock-on exchange potentials, for n${\mathrm{-}}^{16}$O scattering at laboratory energies of 20 and 50 MeV. The model uses the complex and density dependent n-n interaction of N. Yamaguchi et al. uses harmonic oscillator wave functions for the bound nucleons, and calculates the scattering wave function for this nonlocal problem using a Bessel-Sturmian expansion method incorporating correct boundary conditions. All spins are neglected. The local phase-equivalent potential is obtained from the scattering matrix elements at a given energy by using the iterative perturbative inversion method. This representation allows comparison between the microscopic model and a phenomenological potential, showing good agreement for the local real part of the potential at 20 MeV. From the ratio of the wave functions for the nonlocal potential and for the potential calculated by inversion, a Perey damping factor (PDF) is obtained which is of similar form to the well-known Perey-Buck prescription for the PDF for a Gaussian nonlocality of the conventional range of 0.85 fm. The significance of these results for distorted wave Born approximation calculations is discussed.

The Z distributions of fragments emitted from central collisions of ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$${+}^{45}$Sc at beam energies from 15 to 115 MeV/nucleon have been fitted to power laws σ(Z)∝${\mathit{Z}}^{\mathrm{-}\lambda }$. The λ parameter reaches a minimum at a beam energy of 23.9±0.7 MeV/nucleon. A percolation model calculation reproduces the observed Z distributions for all beam energies, using the mean excitation energy as extracted from proton kinetic energy spectra. We extract the critical value of the deposited excitation energy for our system and make predictions for the dependence of this quantity on the size of the fragmenting system.

Following previous works where the field of application of Glauber methods were extended to heavy-ion scattering in the energy range of 30–400 MeV/nucleon, we develop here a formalism which includes both Coulomb and nuclear excitation processes and explicitly accounts for the effects arising from the energy difference in different channels. First order inelastic excitations are described in the framework of a distorted wave eikonal approximation; in this connection nuclear phase shifts and form factors are described in terms of microscopic nucleon-nucleon interactions while the Coulomb excitation is described through a proper manipulation of phenomenological form factors. Several specific examples are discussed. The interest is then focused on second-order processes, more specifically on the effects introduced in the elastic channel by the coupling to the inelastic channels, and the corresponding Coulomb and nuclear polarization potentials are derived and discussed. On the ground of these achievements a general formalism is built up, capable of describing coupled-channel problems at any order of scattering. Due to the eikonal propagation, the multichannel multistep series leads to simple algebraic forms for each partial-wave scattering matrix, which involve powers of a channel matrix whose elements only depend on the impact parameter.