Collisional damping of nuclear collective vibrations is studied within the framework of the Vlasov-Landau equation including retardation (memory) effects in the collision integral. Expressions for the nuclear two-body viscosity and the collisional width Γ of the giant multipole resonances in heated nuclei are obtained in the case of the quadrupole dynamic distortion of the Fermi surface. An improved formula for Γ is also proposed in which all multipolarities of the distortion of the Fermi sphere are taken into account. The collisional width of the giant dipole resonance is calculated as a function of excitation energy for the Sn nuclei region using this formula. It shows a weak variation with temperature. In the temperature range of T≊2.5–7 MeV, the contribution of collisional damping to GDR width does not exceed 50% of the experimental values.

Large-basis shell model studies of low-lying excitations in light nuclei from ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ to ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ have been performed with a multivalued G-matrix effective interaction, as recently suggested by Haxton et al. Calculations were performed relative to the vacuum (‘‘no core’’) using very large, separable model spaces containing all excitations with unperturbed energies up to 8ħΩ. Using G matrices derived from a new Nijmegen potential, we achieve a very satisfactory description of these excitations.

Employing a non-Markovian collision term, the relaxation rates of giant resonances in nuclei are calculated using a diffuse nuclear surface, and energy and angle dependent cross sections obtained by a parametrization of the nucleon-nucleon scattering data. The calculations show that the collisional damping of giant quadrupole vibrations is sizable and accounts for about 40–60 % of the observed widths, while for giant dipole and giant monopole vibrations it accounts for only 25–30 % of the observed widths.

We investigate the role of the effective nucleon-nucleon interaction in the description of giant dipole resonances in hot nuclei. For this purpose we calculate the response function of hot nuclear matter to a small isovector external perturbation using various effective Skyrme interactions. We find that for Skyrme forces with an effective mass close to unity an undamped zero sound mode occurs at zero temperature. This mode gives rise in finite nuclei (calculated via the Steinwedel-Jenssen model) to a resonance whose energy agrees with the observed value. We find that zero sound disappears at a temperature of a few MeV, leaving only a broad peak in the dipole strength. For Skyrme forces with a small value of the effective mass (0.4), there is no zero sound at zero temperature but only a weak peak located too high in energy. The strength distribution in this case is nearly independent of temperature and shows small collective effects. The relevance of these results for the saturation of photon multiplicities observed in recent experiments is pointed out.

Based on the arguments of excitation energy systematics and alignment additivity rule, the spins of the lowest observed states of the (${\mathit{h}}_{11/2}$${)}_{\mathit{p}}$(${\mathit{i}}_{13/2}$${)}_{\mathit{n}}$ bands in ${}_{}{}^{156}{}_{}{}^{}\mathrm{Tb}$, ${}_{}{}^{158}{}_{}{}^{}\mathrm{Ho}$, ${}_{}{}^{166}{}_{}{}^{}\mathrm{Lu}$, and ${}_{}{}^{168}{}_{}{}^{}\mathrm{Ta}$ are assigned as 8, 9, 8, and 9 instead of the previous assignments of 6, 6, 7, and 10, respectively. Taking these new spin assignments and the preliminary experimental results of ${}_{}{}^{162,164}{}_{}{}^{}\mathrm{Lu}$ into account, the systematic features of the signature inversion of the (${\mathit{h}}_{11/2}$${)}_{\mathit{p}}$(${\mathit{i}}_{13/2}$${)}_{\mathit{n}}$ bands of the doubly odd nuclei in the lighter rare-earth region (around A∼160) are presented.

The systematics for the excitation energies of the ground, β, and γ bands are presented using the empirical total np interaction ${\mathit{V}}_{\mathit{NP}}$. Some regularities found in the previous studies are tested by the systematics in the ${\mathit{V}}_{\mathit{NP}}$ schemes. The systematics of the β and γ bands are presented in detail. Elegant regularities are observed for the excitation energies. The correlation phenomenon of the general behavior among different bands within each major shell is pointed out.

As part of an experimental study of the πNN system, the pion-deuteron breakup reaction ${\mathrm{\pi }}^{+}$d→→pn${\mathrm{\pi }}^{+}$ was investigated at intermediate energies. Distributions of the vector analyzing power ${\mathit{iT}}_{11}$ versus outgoing proton momentum ${\mathit{P}}_{\mathit{p}}$ are presented for 36 πp angle pairs in the range of scattering angles 20°≤${\mathrm{\theta }}_{\mathit{p}}$≤51°, 62°≤${\mathrm{\theta }}_{\mathrm{\pi }}$≤124° at 228 and 134 MeV. These include 7 previously unmeasured angle pairs at 228 MeV and 20 new pairs at 134 MeV. In all regions of overlap with previous measurements, there is excellent agreement. There is generally excellent agreement with relativistic Faddeev predictions, except in the np final-state interaction region at 228 MeV. This is in contrast to the cross-section measurements, which are not well described by the theory.

Using the neutron time-of-flight facility at the Indiana University Cyclotron Facility we have studied (p,n) reactions on the light nuclei ${}_{}{}^{6,7}{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^{10,11}{}_{}{}^{}\mathrm{B}$, and ${}_{}{}^{12,13}{}_{}{}^{}\mathrm{C}$. Double differential cross sections have been measured between ${\mathrm{\theta }}_{\mathrm{lab}}$=0° and 50° in 5° intervals, at ${\mathit{E}}_{\mathit{p}}$=186 MeV. Contributions of the quasifree reaction in the giant resonance region are estimated. Energy spectra of ΔL=1 transitions have been extracted using multipole decomposition analysis. The resulting ΔL=1 spectra are compared with results of photonuclear reactions. Empirical results are also compared with distorted wave impulse approximation calculations.

The isomeric cross-section ratio ${\mathrm{\sigma }}_{\mathit{m}}$/(${\mathrm{\sigma }}_{\mathit{m}}$+${\mathrm{\sigma }}_{\mathit{g}}$) for the formation of ${}_{}{}^{75}{}_{}{}^{}\mathrm{Ge}_{}^{\mathit{m},\mathit{g}}{}_{}{}^{}$ was measured in ${}_{}{}^{75}{}_{}{}^{}\mathrm{As}$(n,p), ${}_{}{}^{78}{}_{}{}^{}\mathrm{Se}$(n,α), and ${}_{}{}^{76}{}_{}{}^{}\mathrm{Ge}$(n,2n) processes in the neutron energy range of 6.3 to 14.7 MeV. Use was made of the activation technique in combination with high-resolution γ-ray spectrometry. The ratio is relatively high (≳0.70) even at low incident particle energies and appears to increase only slightly with increasing energy. Statistical model calculations, taking into account precompound effects, were performed for the total reaction channel as well as for the isomer ratio. In either case, good agreement was obtained. For the investigated isomeric pair, no significant effect of reaction channels on the isomeric cross-section ratio was observed.

We measured the analyzing power ${\mathit{A}}_{\mathit{y}}$ and the triple differential cross section ${\mathit{d}}^3$σ/d${\mathrm{\Omega }}_{\mathit{pd}}$${\mathrm{\Omega }}_{\mathit{ndE}\mathit{p}}$ for the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(p→,pn${)}^1$H reaction at 200 MeV. Coplanar coincidence data were taken for all combinations of neutron angles ${\mathrm{\theta }}_{\mathit{n}}$=35°, 45°, or 55° with proton angles ${\mathrm{\theta }}_{\mathit{p}}$=35°, 45°, or 52°. Protons were detected with a ΔE-E telescope with a 1000-μm silicon surface barrier ΔE detector and a plastic scintillator E detector. Neutrons were detected with large-volume plastic scintillators at flight paths of 17.5 or 18 m. The overall neutron separation-energy resolution was about 3 MeV. Data are compared with plane-wave impulse-approximation calculations with a Hulthén deuteron wave function and p-n cross sections and analyzing powers obtained from N-N phase shifts. The agreement between these calculations and the data is generally good for the cross sections. The agreement for the analyzing powers is good near the point of zero recoil momentum. Our results suggest that the deuteron is a good ‘‘neutron target’’ for recoil momenta <100 MeV/c.

We have made simultaneous measurements of singles ($\overrightarrow{p}, {\overrightarrow{p}}^{\prime }$) spin-transfer observables and coincident ($\overrightarrow{p}, p^{\prime }\gamma$) yields and asymmetries for the 15.11 MeV, $1^{+}$, $T=1\mathrm{}$ state in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, at an incident proton bombarding energy of 200 MeV. Data were taken at four proton scattering angles ranging from ${\theta }_p^{\mathrm{c}.\mathrm{m}.\mathrm{}}=5.5\mathrm{}° \mathrm{to} 16.5°$. Both vertical (normal to the reaction plane) and horizontal (in-plane) incident beam polarizations were used, which allowed us to extract 16 different observables for this transition. In particular, using the ($\overrightarrow{p}, p^{\prime }\gamma$) reaction, we measured the sideways and longitudinal analyzing powers, $D_{0S}$ and $D_{0L}$, which vanish identically in the ($\overrightarrow{p}, p^{\prime }$) reaction. Detailed comparisons of all observables to calculations done in both relativistic and nonrelativistic formalisms are presented. Surprisingly, a relativistic description in which knock-on exchange processes are not explicitly included provides the best overall agreement with the data.

The excitation functions for production of many residues in the fusion of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ with ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$ and ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ and of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ with ${}_{}{}^{165}{}_{}{}^{}\mathrm{Ho}$ and ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}$ have been measured at incident energies varying from the Coulomb barrier up to about 10 MeV/nucleon. The cross sections for fusion of these ions without fission have been deduced and they show that such a process may only occur for projectile angular momenta smaller than a critical value. The excitation functions for individual reactions provide evidence for the emission of preequilibrium nucleons during the thermalization of the composite nucleus and may be satisfactorily reproduced by a calculation based on the Boltzmann master equation theory.

Recently nonlocal distorted wave impulse approximation (DWIA) calculations for A(γ,πN)B photopion production reactions have been reported. In this paper we examine the factorized DWIA formulation to help clarify some of the underlying physics content inherent in such measurements. We also extend the formulation to the case of polarized targets and to the measurement of the emitted nucleon polarization. We show that with reasonable approximations one can formally write the three-body reaction spin observables in terms of products of the two-body γ+N→π+N spin observables, the polarization of the struck nucleon which depends on nuclear structure, and an effective polarization created by the distortions. Calculations are presented for two nuclear targets for which adequate polarization has been obtained to utilize them in experiments; viz., ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$. These calculations provide typical predictions which might be compared to experimental data to search for evidence of medium modifications of the pion production amplitudes.

The Euclidean proton and nucleon responses of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ at q=10 ${\mathrm{fm}}^{\mathrm{-}1}$, evaluated with the correlated Glauber approximation using a realistic nucleon-nucleon interaction and nonrelativistic kinematics, are compared to those obtained from the Green’s function Monte Carlo approach. The results show that final state interactions play a crucial role even at this large value of q, and that their effect can be quantitatively accounted for with the correlated Glauber approximation.

Nucleation theory based on the steady-state solution of Fokker-Plank kinetic equation is applied to study of the liquid-gas phase transition in nuclear matter. Theoretical predictions are compared with the parameters extracted from the analysis of the charge distributions of fragments in heavy ion collisions at intermediate energies. The phenomenological droplet model is shown to be able to explain both the characteristic power-law falloff and the long tail of the yields of light and heavy nuclear fragments correspondingly. It is shown that the traditional equilibrium approach to the analysis of the multifragmentation data leads to significant overestimation of the parameters of nuclear equation of state.

Recently published data for the elastic scattering of 70.5 MeV polarized ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ by ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ have been compared with the results of coupled-channels calculations. The diagonal and off-diagonal potentials used in the analysis were generated from phenomenological α + ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ and d→ + ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ optical potentials via the cluster-folding method. Examined were the effects of projectile excitation to the three low-lying T=0 resonant states and to nonresonant continuum states in the energy range 0.63 MeV–10.03 MeV, relative to the ${}_{}{}^6{}_{}{}^{}\mathrm{\alpha }$+d breakup threshold at 1.47 MeV. In common with earlier analyses, calculations limited to the resonant excited states reproduced the data only when the interaction and coupling potentials were renormalized. However, the inclusion of the nonresonant excited states removed the need for this renormalization. Calculations including both the resonant and nonresonant states yielded a description of the differential cross section data superior to that resulting from calculations limited to the resonant states even when the latter were performed with renormalized potentials. Calculations of the tensor analyzing powers reproduced the data well and favored a near zero value for the spectroscopic amplitude of the D-state admixture in the ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ ground state cluster wave function.

We propose a model based on quantum molecular dynamics (QMD) incorporated with a statistical decay model (SDM) to describe various nuclear reactions in a unified way. In this first part of the work, the basic ingredients of the model are defined and the model is applied systematically to the nucleon- (N-)induced reactions. It has been found that our model can give a remarkable agreement in the energy-angle double differential cross sections of (N,${\mathit{xN}}^{\prime }$) type reactions for incident energies from 100 MeV to 3 GeV with a fixed parameter set. A unified description of the three major reaction mechanisms of (N,${\mathit{xN}}^{\prime }$) reactions, i.e., compound, preequilibrium, and spallation processes, is given with our model.

The components of the nuclear inertia tensor, functions of the separation distance R and of the radius of the light fragment ${\mathit{R}}_2$, ${\mathit{B}}_{\mathit{RR}}$(R,${\mathit{R}}_2$), ${\mathit{B}}_{\mathit{RR}2}$(R,${\mathit{R}}_2$), and ${\mathit{B}}_{{\mathit{R}}_2{\mathit{R}}_2}$(R,${\mathit{R}}_2$) are calculated within the Werner-Wheeler approximation, by using the parametrization of two intersected symmetric or asymmetric spheres. Analytical relationships are derived. When projected to a path ${\mathit{R}}_2$=${\mathit{R}}_2$(R), the reduced mass is obtained at the touching point. The two one-dimensional parametrizations with ${\mathit{R}}_2$=const, and the volume ${\mathit{V}}_2$=const previously studied, are found to be particular cases of the present more general approach. Illustrations for the cold fission, cluster radioactivity, and α decay of ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$ are given.

We measured neutron triple-differential cross sections from multiplicity-selected Au-Au collisions at 150A, 250A, 400A, and 650A MeV. The reaction plane for each collision was estimated from the summed transverse velocity vector of the charged fragments emitted in the collision. We examined the azimuthal distribution of the triple-differential cross sections as a function of the polar angle and the neutron rapidity. We extracted the average in-plane transverse momentum 〈${\mathit{P}}_{\mathit{x}}$〉 and the normalized observable 〈${\mathit{P}}_{\mathit{x}}$/${\mathit{P}}_{\mathrm{\perp }}$〉, where ${\mathit{P}}_{\mathrm{\perp }}$ is the neutron transverse momentum, as a function of the neutron center-of-mass rapidity, and we examined the dependence of these observables on beam energy. These collective flow observables for neutrons, which are consistent with those of protons plus bound nucleons from the Plastic Ball Group, agree with the Boltzmann-Uehling-Uhlenback (BUU) calculations with a momentum-dependent interaction. Also, we calculated the polar-angle-integrated maximum azimuthal anisotropy ratio R from the value of 〈${\mathit{P}}_{\mathit{x}}$/${\mathit{P}}_{\mathrm{\perp }}$〉.

Interactions of $10.6A$ GeV gold nuclei have been studied in nuclear emulsions. In a minimum bias sample of 1100 interactions, 4730 helium nuclei and 2102 heavy nuclei were emitted as fragments of the incident gold projectiles. The emission angles of these fragments have been measured and pseudorapidity distributions constructed. The multiplicity distributions have been considered separately for the light and heavy target nuclei in the emulsions and found to be relatively independent of the nature of the target, when studied in terms of the total charge remaining bound in the multiply charged fragments. These distributions have been compared with those reported by experiments that studied the multifragmentation of 0.6 and $1.0A$ GeV gold nuclei, and show relatively small but statistically significant differences that may be attributed to the differing energies or, possibly, to detection biases in the low energy data. We have also looked for evidence of phase changes in the description of multifragmentation and compared our conclusions with those of a study of $1.0A$ GeV gold nuclei interacting in a carbon target. We see evidence of behavior that is similar, but not entirely consistent, with that reported at the lower energy. Whether this is evidence for a true phase change in the state of the nuclear matter remains an open question.