We study effects of the mean field in hot compressed nuclear matter in the context of the Vlasov Uehling-Uhlenbeck theory. The expansion of a spherical distribution at different temperatures is studied along with collisions of Nb+Nb and Au+Au at lab energies from 50 to 1050 MeV/nucleon. In both the expansion and the actual heavy ion collision simulation, a transition behavior is seen only at the lowest temperature (T<10 MeV) or bombarding energy (E=50 MeV/nucleon), where the attractive part of the mean field is able to bind the expanding matter. At the lowest energy one thus sees the formation of a central residue, whereas at higher bombarding energies there is complete disintegration of the centrally colliding nuclei. The spectrum of emitted nucleons is found to be much hotter than the kinetic energy spectrum of the central emitting region. The extracted temperature slope parameters are in agreement with recent data.

We have performed time-dependent Hartree-Fock calculations for the ${}_{}{}^{16}{}_{}{}^{}$O${+}^{16}$O system using various parametrizations of the Skyrme force. These calculations also include the spin-orbit part of the Skyrme force. We have refitted the finite-range version of the Skyrme force to the ground state properties of eight nuclei with improved accuracy. Particular emphasis is given to comparisons of calculations with and without the spin-orbit force. We see a strong sensitivity of the results to the different parametrizations of the effective interaction. The spin-orbit force introduces a significant enhancement of the dissipation. A schematic model of heavy-ion scattering is used to investigate the origin of the observed sensitivity. We find that the dissipation is essentially determined by the additional residual interaction.

The reaction ${}_{}{}^{13}{}_{}{}^{}\mathrm{Li}$,p), at a bombarding energy of 28 MeV, has been used to populate states of ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ up to an excitation energy of 16 MeV. Complete angular distributions were measured and compared with results of standard Hauser-Feshbach calculations. The overall magnitudes of the cross sections are reasonably well reproduced. A preponderance of slight forward peaking in the data suggests the presence of an additional nonstatistical mechanism.

Excitation functions have been measured for different charge products of the ${}_{}{}^{28}{}_{}{}^{}$Si${+}^{48}$Ti reaction in the laboratory energy range 120–127 MeV in 250-keV steps at ${\theta }_{\mathrm{lab}=28\mathrm{}\mathrm{°}}$, 32°, and 40°. Coherence energies of dissipative cross sections have been evaluated by statistical fluctuation analysis. The role of the angular dependence of the coherence energy in determining the interaction time is discussed.

Multifragmentation in heavy ion collisions is studied with the quantum statistical model. It is shown that stable and instable medium-mass fragments are abundantly produced. The degree of dissociation, which can be measured by the number of charged particles emitted, $M_c$, divided by the total number, $N_p$, of charges in the system, is proposed as a measure of the entropy of the system.

We calculate pion spectra within three simple models of pion production in relativistic heavy ion collisions. All three models are based on particle freeze-out from thermal and chemical equilibrium. In the first one, nucleons, pions, and Δ resonances freeze out at a fixed temperature and density. The spectra are a superposition of thermal pions and pions from the decay of the Δ resonance. In the second model, we assume that pions are radiated from a hot, spherical source of nuclear matter, which loses energy because of this radiation. In the last calculation, we employ a hydrodynamic model of the expansion process to determine the pion spectra produced by a sequential freeze-out at fixed density and different times and temperatures. Only this last model gives a shape of the pion distribution similar to the experimental one. It is found that three different effects contribute to the concave shape of the spectra in this model.

We investigate the effects on the elastic S matrix of the coupling to α-transfer channels. On the basis of a separable approximation for the propagator in the transfer channel, we obtain simple expressions for the elastic S matrix which include effects of the coupling to all orders. These expressions are used to study the elastic scattering of ${}_{}{}^{16}{}_{}{}^{}$O${+}^{28}$Si at 180°. It is shown that a standard two-step distorted-wave Born approximation treatment of the coupling is unable to explain the order of magnitude of the data. On the other hand, the inclusion of high-order processes leads to a qualitative agreement with the data. This modification in the results was traced down to the appearance of a pole in the elastic S matrix near the real axis. The S matrix calculated here was shown to be consistent with others obtained phenomenologically from fits to the available data. We suggest that the apparent importance of α-transfer effects in elastic scattering implies that such processes should be relevant in other nuclear reactions involving nα nuclei.

High-spin states of ${}_{}{}^{100}{}_{}{}^{}\mathrm{Cd}$ up to $J^{\pi }$${=8\mathrm{}}^{+}$ and an excitation energy of 2.5 MeV were studied by means of the ${}_{}{}^{64}{}_{}{}^{}\mathrm{Zn}$${(}^{40}$Ca,2p2nγ${)}^{100}$Cd reaction. The $J^{\pi }$${=8\mathrm{}}^{+}$ state was found to be isomeric with a half-life of 73±5 ns. The proposed level scheme is in agreement with that proposed recently by Alber et al. and is discussed in terms of expectations for the spectrum of a unique ‘‘pseudomagic’’ nucleus, i.e., an isobar of doubly magic ${}_{}{}^{100}{}_{}{}^{}\mathrm{Sn}$ which possesses a hole pair (protons) and a particle pair (neutrons) away from the magic number 50. Simultaneously, the ${}_{}{}^{64}{}_{}{}^{}\mathrm{Zn}$${(}^{40}$Ca,3p2nγ${)}^{99}$Ag reaction was observed to populate states of ${}_{}{}^{99}{}_{}{}^{}\mathrm{Ag}$ up to $J^{\pi }$${=\left(\right(27/2\mathrm{}}^{+}$). The excitation energies of both nuclides are compared to those found recently for the lighter isotones ${}_{}{}^{96}{}_{}{}^{}\mathrm{Ru}$, ${}_{}{}^{97}{}_{}{}^{}\mathrm{Rh}$, and ${}_{}{}^{98}{}_{}{}^{}\mathrm{Pd}$, and the systematic structures of the N=52 nuclides are discussed.

The differential emission probability for a neutron emitted in a binary fission process due to nonadiabatic effects in the coupling of the single-particle degrees of freedom to the accelerated relative motion of the fragments is investigated within a model which represents each nucleus by a nondeformed one-term separable potential. Initially the neutron is bound in a two-center eigenstate, referring to a certain separation distance of the centers of the potentials. The collective relative motion is assumed to proceed with zero angular momentum along a trajectory which is calculated from classical equations of motion including conservative and phenomenological frictional forces. The derivation of measurable quantities from the asymptotic solution of the time-dependent Schrödinger equation for the single particle wave function is carefully examined. Numerical calculations have been performed for parameter values which simulate ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$(sf). The calculated energy spectra and angular distributions of the emitted particles are presented for different values of the mass asymmetry.

The optical model potential for medium energy nucleons is calculated from a momentum and density dependent force which is derived from Brueckner’s reaction matrix in a nuclear matter approximation. It is found that Pauli blocking effects substantially increase the nonlocality of the reaction matrix. Calculated optical model parameters are compared with those obtained from the conventional approach of a localized effective two-nucleon force. Proton elastic scattering observables on ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ targets at $E_{\mathrm{p}=135\mathrm{}–}$300 MeV are analyzed.

The optical phase shift function is calculated to fifth order in a model in which center of mass correlations in the nucleus are taken into account. Differential cross sections are calculated for elastic scattering of protons by ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. The results are compared with exact Glauber calculations and with a simple $t_0$ρ-type approximation. The significance of the higher-order corrections is assessed.

Calculations have been performed for the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${\mathrm{K}}^{\mathrm{-}}$,${\mathrm{\pi }}^{\mathrm{-}}$${)}_{\mathrm{\Sigma }}^{12}$C, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${\mathrm{K}}^{\mathrm{-}}$,${\mathrm{\pi }}^{+}$${)}_{\mathrm{\Sigma }}^{12}$Be, and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${\mathrm{K}}^{\mathrm{-}}$,${\mathrm{\pi }}^{\mathrm{-}}$${)}_{\mathrm{\Lambda }}^{12}$C reactions with stopped kaons. A g-matric YN interaction is employed in structure calculations with the recoil corrected continuum shell model. This provides a realistic prediction of the hypernuclear structure above the hyperon escape threshold. The ΣN→ΛN conversion process is treated by both absorption in the ΣN interaction and by effective lambda channels in separate calculations. Both seem to be necessary for a complete representation of capture rates. No observable structure is predicted due to substitutional states in ${}_{{}_{\mathrm{\Sigma }}{}^{12}{}_{}{}^{}}{}^{}{}_{}{}^{}\mathrm{Be}$. The substitutional states in ${}_{{}_{\mathrm{\Sigma }}{}^{12}{}_{}{}^{}}{}^{}{}_{}{}^{}\mathrm{C}$ are obscured by a large quasifree background. It is concluded that experiments based on capture of stopped kaons will not provide definitive information on the structure of Σ hypernuclei.

Lorentz scalar and four-vector optical potentials are obtained for protons elastically scattered from ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. It is demonstrated that Dirac optical potentials constrained by relativistic Hartree theory are capable of producing good agreement with experiment.

Forward-angle cross sections for $1^{+}$, T=1 and $1^{+}$, T=0 states in ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ excited by the (p,p’) reaction have been measured to determine the energy dependence of important pieces of the effective nucleon-nucleus interaction. The isovector spin-transfer transitions depend on energy as expected from distorted-wave impulse approximation calculations based on the dominant $V_{\sigma \tau }$ part of the Franey-Love interaction. The parts of this interaction responsible for exciting the 9.5 MeV isosca- lar spin-flip transition predict a weaker energy dependence than is observed experimentally. The summed Gamow-Teller strength for isovector transitions below 14.5 MeV is found to be (0.89±0.09) times the result of large-scale shell model calculations.

A recent publication presented angular distributions for 180-MeV pion inelastic scattering for several N∼28 nuclei. Proton E2 matrix elements extracted from those data for certain states were systematically larger than those inferred from γ decay. A possible explanation for these anomalies is discussed.

We formulate a systematic approximation to the Dirac-Hartree description of closed-shell ±1 nuclei using the closed-shell basis. Expectation values of one-body operators include random-phase-approximation-like loop corrections to the single particle (or hole) results. We use a nonspectral form of the Hartree propagator which allows inclusion of positive- and negative-energy continuum contributions exactly. The loop corrections quench the single-particle isoscalar magnetic moments back to the Schmidt values, resulting in good agreement with experiment. Elastic M1 electron scattering form factors are also quenched at low q. However, the loop corrections vanish at q≃1.2 ${\mathrm{fm}}^{\mathrm{-}1}$ and change sign so as to enhance the single-particle result at still higher momentum transfers. This raises the possibility that experimental signatures of the strong relativistic nuclear dynamics characteristic of Dirac-Hartree models may be present in elastic M1 form factors for closed-shell ±1 nuclei.

A method for defining a separable approximation to a given interaction within a two-body relativistic equation, such as the Bethe-Salpeter equation, is presented. The rank-N separable representation given here permits exact reproduction of the T matrix on the mass shell and half off the mass shell at N selected bound state and/or continuum values of the invariant mass. The method employed is a four-space generalization of the separable representation developed for Schrödinger interactions by Ernst, Shakin, and Thaler, supplemented by procedures for dealing with the relativistic spin structure in the case of Dirac particles.

The longitudinal response function for quasielastic electron scattering is calculated in the σωρ model of quantum hadrodynamics. We use meson fields and nucleon wave functions, as obtained in mean-field theory of closed-shell nuclei, in relativistic random-phase approximation. The results for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ are compared with those of a previous calculation, where the response function was evaluated in local-density approximation. We find a shift in the position of the maximum which is due to the inclusion of binding energy effects, and a slight broadening of the response function. Comparing with the data, we find good agreement except for ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ at the highest momentum transfer q=550 MeV.

Cross sections for the elastic scattering of positive and negative pions from calcium at 19.5 and 30 MeV were measured at scattering angles between 18° and 110°. They are compared to the angular distributions predicted by three optical models. Both 19.5 and 30 MeV data agree best with the predictions of a potential whose strengths are taken from a phenomenological potential designed to reproduce anomalously small level shifts and widths in pionic atoms.

The energy dependence of the (p,${\pi }^{\mathrm{-}}$) and (p,${\pi }^{+}$) reactions on ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ leading to isobaric analog states of ${}_{}{}^{14}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ has been measured at a fixed four-momentum transfer at proton lab energies of 250, 354, and 489 MeV. Unlike the (p,${\pi }^{+}$) reactions, which show an enhancement of the differential cross section near the invariant mass of the ${\Delta }_{1232}$ similar to that observed for the pp→d${\pi }^{+}$ reaction at an equivalent center of mass energy and momentum transfer, the differential cross section of the (p,${\pi }^{\mathrm{-}}$) reactions decrease with increasing energy through this region. This difference is consistent with an interpretation of the (p,${\pi }^{\mathrm{-}}$) reaction mechanism as a NN→NN${\pi }^{\mathrm{-}}$ process in which nonresonant amplitudes are dominant in this region.