We examine the influence of momentum-dependent interactions on the momentum flow in 400 MeV/nucleon heavy ion collisions. Choosing the strength of the momentum dependence to produce an effective mass $m^{\mathrm{*}}$=0.7m at the Fermi surface, we find that the characteristics of a stiff equation of state can be obtained with a much softer compressibility.

We suggest a quantum mechanical interpretation of the density matrix of the time-dependent Hartree-Fock theory for heavy ion scattering. We show how with this interpretation the time-dependent Hartree-Fock equations can be derived provided we admit (i) a generalized factorization of a suitably defined average of two-body density matrix elements in terms of a sum of products of the corresponding one-particle elements and (ii) additional semiclassical approximations which convert a sum of products into an antisymmetric product of sums. These ideas, previously recognized within the framework of soliton models, are extended here to include inelastic processes with the excitation of collective modes as the mechanism for producing deep inelastic scattering. An essential feature of the approach is that it provides, in principle, a theoretical method of obtaining exclusive amplitudes. We describe how these might be calculated.

Direct measurements of total reaction cross sections (${\sigma }_R$) have been performed in the energy range of 10–300 MeV/nucleon for heavy ion collisions. A decrease of ${\sigma }_R$ with increasing energy was observed for a wide range of masses of the colliding systems. The data suggest that ${\sigma }_R$ reaches a minimum located around 300 MeV/nucleon independently of the projectile target combination. A dependence of ${\sigma }_R$ on mass asymmetry of the system is also demonstrated. Trends of ${\sigma }_R$ in this energy range are well reproduced by the predictions of a simple microscopic model based on individual nucleon-nucleon collisions. Our data have been employed in this framework to derive a new semi- empirical parametrization of ${\sigma }_R$. Most of the experimental results in the intermediate and high energy range have been reproduced by this parametrization using a single energy-dependent parameter.

Statistical model calculations for the interaction of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ with ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ at 30 MeV show that a considerable fraction of the carbon production is produced via complete fusion. This result suggests that the continuum cross section of 700±125 mb measured earlier for ${}_{}{}^6{}_{}{}^{}$Li${+\mathrm{}}^{12}$C has carbon fusion residuals included in the sum and hence does not arise solely from direct breakup. Statistical model calculations are able to predict the background continuum in the carbon energy spectra and when used with measured angular distributions determine a direct breakup cross section of 390 mb. Measured alpha spectra for the ${}_{}{}^6{}_{}{}^{}$Li${+\mathrm{}}^{12}$C reaction are also presented. They provide a further test of the statistical model predictions for ${}_{}{}^6{}_{}{}^{}$Li${+\mathrm{}}^{12}$C.

Two-particle correlations at small relative momenta provide information about the space-time extent and the excitation energy density of the emitting system. Detailed measurements of two-particle correlations were performed for ${}_{}{}^{40}{}_{}{}^{}\mathrm{induced}$ reactions on ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ at E/A=60 MeV. In general, more pronounced correlations are measured for particles of higher outgoing energy. From the relative populations of excited states, a mean emission temperature of T≊5.5 MeV is extracted. Within the framework of the quantum statistical model, our findings are consistent with an expanding nuclear system which disintegrates at low temperature (T≊5.5 MeV) and rather low density (ρ≤0.1${\rho }_0$).

A model based upon nucleon-nucleon (n-p) bremsstrahlung is presented as a possible explanation of high energy γ rays produced in heavy-ion collisions. A semiclassical bremsstrahlung formula is ‘‘calibrated’’ to p+d bremsstrahlung data, then incorporated into the Boltzmann master equation as a means for following the nucleon-nucleon collisions. The input parameters to the master equation are taken from previous studies of preequilibrium nucleon spectra, eliminating all free parameters from our calculation. The results of this calculation are compared to the available high energy γ-ray data, with generally excellent agreement. Data taken with lead glass detectors are generally underestimated in our model calculation.

We present a model that provides a unified description of fusion and the full momentum transfer component of dissipative collisions (orbiting), in light-heavy-ion-induced reactions. The model is applied successfully to describe measured cross sections for fusion and orbiting over a wide range of bombarding energies for the ${}_{}{}^{28}{}_{}{}^{}$Si${+}^{12}$C system.

Angular distributions have been measured for the ${(}^6$Li, ${}_{}{}^6{}_{}{}^{}\mathrm{He}$) reaction on targets of ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^{12}{}_{}{}^{}$,14C, ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$, and ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ at bombarding energies of 35, 25, and 14 MeV/nucleon. The ratios of observed cross sections for states in ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ and ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ suggest that the reaction mechanism is predominantly one-step at 35 and 25 MeV/nucleon with an increasing contribution from sequential transfer at lower energies. Measured forward-angle cross sections for Gamow-Teller transitions are found to be accurately proportional to the corresponding B(GT) values from ${\beta }^{\mathrm{-}}$ decay or from (p,n) data. This calibration will allow the measurement of spin-transfer strength with the ${(}^6$Li, ${}_{}{}^6{}_{}{}^{}\mathrm{He}$) reaction at intermediate energies. One-step distorted-wave Born approximation calculations, which used Yukawa central and $r^2$× Yukawa tensor potentials, are consistent with the data at 35 and 25 MeV/nucleon except for ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}<3\mathrm{}}$°, and give a central force strength, $V_{\sigma \tau }$, in reasonable agreement with that obtained in (p,n) studies at similar energies per nucleon.

The competition between pn and d evaporation leading to production of the same residual nucleus has been calculated in the framework of the Hauser-Feshbach theory for nine heavy-ion-induced nuclear reactions, each at several bombarding energies, for target-projectile combinations resulting in compound nuclei 12≤A≤40. The observed very good agreement between the experimental and the statistically predicted relative cross sections for pn and d emission indicates that both these exit channels proceed via evaporation from a compound nucleus.

The emission of intermediate rapidity fragments with A≤14 has been studied in 42 to 151 MeV/nucleon Ar- and Ne-induced reactions on Al, Ca, and Au targets. The energy spectra were fitted assuming emission from a single source moving with a velocity intermediate between that of the projectile and target. The extracted temperatures were independent of fragment mass, indicating that the fragments had a common source. The spectra for fragments as heavy as nitrogen were also well described using the coalescence model and the resulting coalescence radii were independent of fragment mass. The observed fragment production cross sections were fitted with a quantum statistical model from which the entropy produced was extracted. This entropy was found to be much less than that derived from d/p ratios and higher than the entropy displayed by target-like fragments. The light particle spectra were compared to a model utilizing a solution of the Boltzmann equation incorporating mean field and Pauli blocking effects to describe the proton spectra from Ar + Ca. Nuclear fluid dynamics calculations agreed reasonably well with the higher energy data but could not describe the 42 MeV/nucleon data.

A molecular orbital theory for the 3α transfer process has been formulated and applied to the ${}_{}{}^{16}{}_{}{}^{}$O${+\mathrm{}}^{28}$Si scattering case. The α transfer mechanism has already been applied successfully in the interpretation of the anomalous large angle scattering between 4N nuclei. It would be worthwhile to test whether the alpha transfer mechanism can also explain the nonstatistical intermediate structure of the excitation function often found in 4N nuclei scattering. The excitation function at 180° is known to be much more sensitive to the details of the optical potential than are the fits to the angular distribution. Both the experimental data of the excitation function at 180° in the energy region from 14 to 52 MeV and all thirteen differential cross sections in the energy region 18.67–34.80 MeV can be fitted well simultaneously with a common set of parameters.

We investigate some of the features of Λ and Σ hypernuclei. The widths of Λ- and Σ-hypernuclear resonances are discussed and estimates made. The coupling between a certain class of Λ- and Σ-hypernuclear states is considered and its relevance to the problem of Σ-hypernuclear widths is indicated.

We formulate a novel relativistic Faddeev theory of the πNN system using a variable-mass isobar ansatz for the πN and NN amplitudes and the requirement that the spectator particles be always on their mass shells. This theory takes into account the two possible time orderings in the propagator of the exchange particle and describes correctly the coupling between the two-body and three-body channels. As a first application of this theory, we study pion-deuteron elastic scattering by calculating all the observables in the region of the 3,3 resonance for which data exist.

The vector analyzing power ${\mathrm{iT}}_{11}$ for pion-deuteron breakup has been calculated at three different energies in the region of the 3,3 resonance and compared with recent data. The calculations have been performed using the relativistic Faddeev theory proposed by the author. The relationship of this theory to other formalisms is discussed, as well as the implications of our results to the question of the existence or nonexistence of dibaryon resonances.

A thick-target, thick-catcher recoil study of the spallation of gold by 100- to 300-MeV ${\pi }^{+}$ and ${\pi }^{\mathrm{-}}$ has been performed. Average ranges and forward-to-backward emission ratios were obtained for 27 products ranging from ${}_{}{}^{196}{}_{}{}^{}\mathrm{Au}$ to ${}_{}{}^{161}{}_{}{}^{}\mathrm{Er}$ in reactions induced by 300-MeV ${\pi }^{+}$; fewer results were obtained at the lower energies as well as for ${\pi }^{\mathrm{-}}$. The results are interpreted in terms of the two-step velocity vector model.

The cross sections of the reactions (γ,p), (γ,pn), and (γ,pp) are measured for ${}_{}{}^1{}_{}{}^{}\mathrm{H}$, ${}_{}{}^2{}_{}{}^{}\mathrm{H}$, ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ in the Δ(1232) resonance region by use of a tagged photon beam. Protons emitted at ${\theta }_{\mathrm{p}=30\mathrm{}}$° are measured by a magnetic spectrometer, and the other neutrons or protons are measured by an array of scintillation counter hodoscopes. From the present experiment, it is concluded that the reactions, γ+‘‘N’’→p+π and γ+‘‘pn’’→p+n, contribute dominantly to the (γ,p) reaction in this energy region, where ‘‘N’’ denotes the nucleon and ‘‘pn’’ denotes the pn system in the nucleus.

A proper treatment of the Pauli principle is usually impossible in Jacobi coordinate representation when heavy nuclei are involved; hence a shell-model representation of the collision becomes mandatory. This raises the traditional problems of shell-model spurious states and recoil corrections. We show how recoil parameters can actually be used as dynamical parameters in collision theories.

The nuclear structure of the N=21 isotones ${}_{}{}^{35}{}_{}{}^{}\mathrm{Si}$ and ${}_{}{}^{36}{}_{}{}^{}\mathrm{P}$ and the N=20 isotones ${}_{}{}^{35}{}_{}{}^{}\mathrm{P}$ and ${}_{}{}^{36}{}_{}{}^{}\mathrm{S}$ is considered in the spherical nuclear shell model with the SDPF interaction. Beta and gamma decay as well as energy spectra are calculated. Results are compared to recent data on ${}_{}{}^{36}{}_{}{}^{}\mathrm{P}$(${\beta }^{\mathrm{-}}$${)}^{36}$S and ${}_{}{}^{35}{}_{}{}^{}\mathrm{Si}$(${\beta }^{\mathrm{-}}$${)}^{35}$P. Unique and nonunique first-forbidden beta decay are considered as well as allowed (Gamow-Teller) decay. The predictions give a good description of the observed features of the four nuclei; in particular, the predicted beta decay rates are in agreement with experiment.

Levels in the ${}_{}{}^{192}{}_{}{}^{}$,194,196,198,200Pb isotopes were studied via the ${\beta }^{+}$/electron-capture decay of mass separated Bi isotopes. Multiscaled spectra of γ rays, x rays, and conversion electrons, and γ-γ and γ-${\mathrm{e}}^{\mathrm{-}}$ coincidences were measured. The existence of $0^{+}$ states in the ${}_{}{}^{192\mathrm{-}200}{}_{}{}^{}\mathrm{Pb}$ nuclei is shown and evidence for the beginning of a collective band built on top of the $0_2^{+}$ states is seen in ${}_{}{}^{192}{}_{}{}^{}$,194,196Pb. A discussion in terms of characteristic properties of intruder states in the even-even nuclei and in terms of a one-broken-neutron-pair formalism is given. This shows clearly the presence of both neutron and proton [π(2p-2h)] based states in the semimagic Pb nuclei at low excitation energy.

The U(5) classical limit of the proton-neutron interacting boson model Hamiltonian, appropriate for the collective $2^{+}$ states, is investigated. The symmetric and mixed-symmetry $2^{+}$ states are identified as arising from the boson-number-weighted symmetric and antisymmetric vibrations in the beta degree of freedom, respectively. Also approximate formulas for the energies away from the U(5) limit and for the reduced matrix elements of the E2 and M1 transition operators are given.