The semiclassical transport theory is applied to the description of heavy-ion fusion at energies below and above the Coulomb barrier. The paths connecting entrance and exit fusion reaction channels are found as a continuous solution of the Vlasov transport equation in classically allowed and forbidden regions associated with suitably defined collective variables. The effects of nuclear deformation, neck formation, and nonlocality are quantified on the basis of microscopic simulations and analyzed. The results of calculations give good fits to experimental data for fusion of nearly symmetric oxygen and nickel isotope pairs.

The fluctuations in the excitation functions of the dissipative collision induced on the ${}^{27}\mathrm{Al}{+}^{27}\mathrm{Al}$ system have been studied in the laboratory energy range 114.2–123 MeV. The amplitude of the fluctuations, the average angular distributions, the energy autocorrelation functions, and the angular correlation functions have been studied in the framework of the partially overlapped molecular level model. The comparisons with the model allow us to estimate the characteristic times involved in the process, the degree of coherent rotations, and the density of molecular states through which the collision evolves. In particular the study of the angular correlations also reveals the coupling effects between rotational and intrinsic degree of freedom of the intermediate dinuclear system.

The Walecka model is studied at finite temperatures in one, two, and three spatial dimensions. The critical temperatures ${(T}_c)$ and densities $\left({\rho }_c\right)$ for the liquid-gas phase transition are calculated in these dimensions. As expected from a mean-field approach, the phase diagram in the ${T/T}_c$ versus $\rho /{\rho }_c$ plane is dimension independent in the vicinity of the critical point. An interesting finding is that, because the critical and “flash” temperatures are proportional, within numerical errors, dimension-independent curves can also be obtained for the incompressibility by scaling with the “flash” point coordinates ${(T}_f,{\rho }_f).\mathrm{}$ At the high-temperature regime, only the two- and three-dimensional systems present a phase transition.

Inclusive double differential multiplicities of deuterons, ${}^3\mathrm{H},$ ${}^3\mathrm{He},$ and ${}^4\mathrm{He}$ measured by E877 for $11.5A\hspace{0.5em}\mathrm{GeV}/c$ Au+Au collisions at the Brookhaven’s Alternating Gradient Synchrotron (AGS) are presented. Light fragments at beam rapidity are measured for the first time at AGS energies. Beam rapidity deuteron and ${}^4\mathrm{He}$ yields and transverse slope parameters are found to be strongly dependent on the impact parameter, and the shape of the deuteron spectra is not consistent with that expected for a simple thermal distribution. The deuteron yields relative to proton yields are analyzed in terms of a simple coalescence model. While results indicate an increase in source size compared to collisions of lighter systems at the same energy, they are inconsistent with a simple coalescence model reflected by a rapidity dependence of the coalescence parameter $B_d.$ A new approach utilizing an expanding thermalized source combined with a coalescence code is developed for studying deuteron formation in heavy-ion collisions. The strong dependence of deuteron yields on collective motion implies that deuteron yields relative to those of protons can be used for constraining source parameters.

Picosecond lifetimes in ${}^{129,130}\mathrm{Ba}$ were determined using the recoil distance technique with a plunger device coupled to an array of EUROBALL-cluster-detectors for the first time. The differential decay curve method in coincidence mode was employed to derive lifetimes for six states in ${}^{129}\mathrm{Ba}$ and twelve states in ${}^{130}\mathrm{Ba}.$ The resulting $B\left(E2\mathrm{}\right)\mathrm{}$ values are compared with triaxial rotor plus particle calculations for ${}^{129}\mathrm{Ba}$ and, in ${}^{130}\mathrm{Ba},$ to the predictions of the general collective model, the interacting boson model, as well as to the symmetric and asymmetric rotor models. In ${}^{130}\mathrm{Ba},$ the transitional quadrupole moment in the ground state band is remarkably constant before and after the backbend. With this data the two-quasiparticle negative parity band in ${}^{130}\mathrm{Ba}$ was confirmed to be based on a $\pi {(h}_{11/2}\otimes d_{5/2}{/g}_{7/2})$ configuration.

Nuclei with large neutron-to-proton ratios have neutron skins, which manifest themselves in an excess of neutrons at distances greater than the radius of the proton distribution. In addition, some drip-line nuclei develop very extended halo structures. The neutron halo is a threshold effect; it appears when the valence neutrons occupy weakly bound orbits. In this study, nuclear skins and halos are analyzed within the self-consistent Skyrme-Hartree-Fock-Bogoliubov and relativistic Hartree-Bogoliubov theories for spherical shapes. It is demonstrated that skins, halos, and surface thickness can be analyzed in a model-independent way in terms of nucleonic density form factors. Such an analysis allows for defining a quantitative measure of the halo size. The systematic behavior of skins, halos, and surface thickness in even-even nuclei is discussed.

The Monte Carlo shell model is a powerful technique for computational nuclear structure. Only a certain class of nuclear interactions, however, such as pairing and quadrupole, is free of the numerical noise known as the sign problem. This paper presents sum rules that relate the sign problem to the $J=0\mathrm{}$ pairing matrix elements, thus illuminating the extrapolation procedure routinely used for realistic shell-model interactions.

The fragments produced in the reaction of ${}^{18}\mathrm{O}{+}^9\mathrm{Be}$ at 60 MeV/nucleon were measured experimentally. The isotopic distribution of the fragmentation reaction products was well reproduced by using a modified statistical abrasion-ablation model. This model predicts that the fragment isotopic distribution at a fixed atomic number Z shifts towards the neutron rich side for the neutron-rich projectile. This isospin effect will decrease with decreasing the fragment atomic number Z and disappear when ${(Z}_{\mathrm{proj}}{-Z)/Z}_{\mathrm{proj}}$ becomes larger than 0.5. It was shown that the disappearance of the isospin effect of fragmentation reaction is induced by the geometry effect in abrasion stage and the evaporation effect later.

A formalism is presented for the calculation of spin transfer cross section for intermediate energy charge exchange ${(}^3\mathrm{He}\to ,\overrightarrow{t})$ [and $(\overrightarrow{p},\overrightarrow{n})]$ reactions to the continuum. The nuclear structure part of the formalism is based on the continuum Tamm-Dancoff method and the nuclear reaction part is treated within the distorted wave impulse approximation. In the nuclear structure part, we thus include particle-hole correlations and continuum effects on the excited particle. The knockon-exchange effect and the damping of the particle through an imaginary potential added to the single particle real potential are also taken into account. Results of numerical calculations are presented for the inclusive cross sections $\sigma \left(0\mathrm{}°\right)$ and the spin transfer coefficients $D_{\mathrm{nn}}\left(0\mathrm{}°\right)$ for forward scattering, for the intermediate energy ${(}^3\mathrm{He}\to ,\overrightarrow{t})$ and $(\overrightarrow{p},\overrightarrow{n})$ reactions on ${}^{12}\mathrm{C}$ and ${}^{90}\mathrm{Zr}$ targets leading to Gamow-Teller resonances in the continuum. It is shown that $D_{\mathrm{nn}}\left(0\mathrm{}°\right)$ for this case takes a value of $-1/3,$ regardless of the details of nuclear structure and reaction mechanisms, if the reaction is assumed to proceed as an orbital angular momentum transfer $l_t=0\mathrm{}$ process, and that deviations from $-1/3$ come from admixture of $l_t=2\mathrm{}$ components. A simple closed form of the expression is derived which can be used to understand a subtle dependence of the $D_{\mathrm{nn}}$ values on nuclear structure and effective interaction.

The absolute γ-ray/fission multiplicities from hot rotating ${}^{240}\mathrm{Cf},$ populated at seven bombarding energies using the reaction ${}^{32}{\mathrm{S}+}^{208}\mathrm{Pb},$ are reported. Statistical model calculations including nuclear dissipation have been performed to extract the dependence of the nuclear viscosity on temperature and/or nuclear deformation. The extracted nuclear dissipation coefficient is found to be independent of temperature. Large dissipation during the saddle to scission path provides a good fit to the γ-ray spectra.

Proton emission from the drip line nucleus ${}_{63}^{131}\mathrm{Eu},$ to the first excited $2^{+}$ state of the daughter nucleus ${}_{62}^{130}\mathrm{Sm}$ is analyzed as decay from a deformed nucleus, and the half-lives are evaluated exactly. It is found that the Nilsson state ${K=3/2\mathrm{}}^{+}$ for a deformation $0.34>\mathrm{}\beta >0.27\mathrm{}$ describes both the fine structure and the decay to the ground state of ${}^{130}\mathrm{Sm}.$

Collective structures in ${}^{178}\mathrm{Pt}$ have been investigated with $\gamma$-ray spectroscopic techniques following mass selection. The present data expand considerably the level scheme of this nucleus. A new collective structure has been identified and the known bands have been extended to higher spins. Firm spin and parity assignments have been made to many levels. Of particular interest are the negative parity bands which are interpreted in terms of structures associated with octupole vibrations crossed at moderate spin by two-quasiparticle excitations. The systematics of the $\alpha$-decay reduced widths in Pt nuclei has also been investigated. The differences of a factor of about 2 between the widths for the odd- and the even-$A$ isotopes is attributed to changes in neutron pairing associated with the blocking effect. The trend is reproduced in calculations based on the Lipkin-Nogami pairing model.

Complementary measurements have been performed for the level density and $\gamma$ strength function in ${}^{162}\mathrm{Dy}$ using inelastic ${}^3\mathrm{He}$ scattering. Comparing these results to previous measurements using the ${}^{163}\mathrm{Dy}{(}^3\mathrm{He},\alpha )$ reaction, reveals that the measured quantities above 1.5 MeV do not depend significantly on the nuclear reaction chosen.

Electron-capture delayed fission of ${}^{242}\mathrm{Es}$ produced via the ${}^{233}\mathrm{U}{(}^{14}\mathrm{N}{,5n)}^{242}\mathrm{Es}$ reaction at 87 MeV (on target) was observed to decay with a half-life of $11\pm 3\mathrm{s},$ consistent with the reported α-decay half-life of ${}^{242}\mathrm{Es}$ of ${16}_{-4}^{+6\mathrm{}}\mathrm{s}.$ The mass-yield distribution of the fission fragments is highly asymmetric. The average pre-neutron emission total kinetic energy of the fragments was measured to be $183\pm 18\mathrm{MeV}.$ Based on the ratio of the measured number of fission events to the measured number of α decays from the electron-capture daughter ${}^{242}\mathrm{Cf}$ (100% α branch), the probability of delayed fission was determined to be $0.006\pm \mathrm{0.002.}$ This value for the delayed fission probability fits the experimental trend of increasing delayed fission probability with increasing Q value for electron capture.

In processes involving Coulomb-type initial- and final-state interactions, the Gamow factor has been traditionally used to take into account these additional interactions. The Gamow factor needs to be modified when the magnitude of the effective coupling constant increases or when the velocity increases. For the production of a pair of particles under their mutual Coulomb-type interaction, we obtain the modification of the Gamow factor in terms of the overlap of the Feynman amplitude with the relativistic wave function of the two particles. As a first example, we study the modification of the Gamow factor for the production of two bosons. The modification is substantial when the coupling constant is large.

We consider an effective Lagrangian containing contributions from glueball and gluon degrees of freedom with a scale-invariant coupling between the two. The thermodynamic potential is calculated taking into account thermal fluctuations of both fields. The glueball mean field dominates at low temperature, while the high temperature phase is governed by low-mass gluonlike excitations. The model shows some similarities to the lattice results in the pure glue sector of QCD. In particular, it exhibits a strong first order phase transition at a critical temperature of approximately 265 MeV when reasonable parameters are taken.

The parity-violating longitudinal asymmetry of the neutron scattering cross section has been measured for thorium in the off-resonance energy intervals from 30 to 300 eV. The observed result of $(0.5\mathrm{}\pm 1.6)\times {10}^{-6}$ is compared with theoretical predictions.

We have made an asymptotic expansion of the effective S factor, $S_{\mathrm{eff}},$ for nonresonant reactions of charged particles. The resulting analytic formulas can generate approximations to $S_{\mathrm{eff}}$ which contain derivatives, with respect to the center of mass energy E, of the astrophysical S factor, $S\left(E\right),$ up to any desired order. Thus our approximation incorporates better the center-of-mass energy dependence in $S\left(E\right)\mathrm{}$ than previous approximations which included only the first or second derivatives. The range of applicability of the method is discussed. We numerically investigate our expressions for the reaction ${}^7\mathrm{Be}(p,\gamma {)}^8\mathrm{B}.$

$\alpha$-nucleus potentials are one important ingredient for the understanding of the nucleosynthesis of heavy neutron-deficient p nuclei in the astrophysical $\gamma$ process where these p nuclei are produced by a series of $(\gamma ,n),$ $(\gamma ,p),$ and $(\gamma ,\alpha )$ reactions. I present an improved $\alpha$-nucleus potential at the astrophysically relevant sub-Coulomb energies which is derived from the analysis of $\alpha$ decay data and from a previously established systematic behavior of double-folding potentials.