${}_{}{}^{97}{}_{}{}^{}\mathrm{Mo}$ nuclei were produced by the ${}_{}{}^{96}{}_{}{}^{}\mathrm{Zr}$${(}^3$He,2nγ${)}^{97}$Mo reaction at 11 MeV. Excitation functions, angular distributions, linear polarizations, and gamma-gamma coincidences were measured and used to construct a ${}_{}{}^{97}{}_{}{}^{}\mathrm{Mo}$ level scheme. By taking advantage of the relatively high Q value of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ reactions, several new non-yrast states were populated and observed. A standard particle-plus-rotor calculation was performed and used to interpret the experimental level scheme. Special emphasis was placed on identifying complete angular momentum multiplets arising from particle-core coupling.

Level structure of ${}_{}{}^{103}{}_{}{}^{}\mathrm{Pd}$ has been studied through the ${}_{}{}^{103}{}_{}{}^{}\mathrm{Rh}$(p,nγ) reaction at incident proton energies ranging from 2.8 to 4.6 MeV. Yield curves for various gamma rays were drawn to check their origin. Lifetimes of various levels were measured at 4.0 and 4.6 MeV incident energy using the Doppler shift attenuation technique. Angular distribution data were analyzed at 4.0 and 4.6 MeV using the Hauser-Feshbach theory of the compound nucleus to extract spin values. Lifetimes of 11 levels at 1273, 1277, 1396, 1581, 1592, 1604, 1679, 1775, 1953, 1964, and 2233 keV were found to be ${75}_{\mathrm{-}10}^{+15\mathrm{}}$, ${65}_{\mathrm{-}16}^{+15\mathrm{}}$, ${35}_{\mathrm{-}5}^{+10\mathrm{}}$, ${60}_{\mathrm{-}10}^{+15\mathrm{}}$, ${280}_{\mathrm{-}60}^{+90\mathrm{}}$, ${80}_{\mathrm{-}10}^{+20\mathrm{}}$, ${20}_{\mathrm{-}4}^{+6\mathrm{}}$, ${140}_{\mathrm{-}15}^{+25\mathrm{}}$, ${70}_{\mathrm{-}10}^{+15\mathrm{}}$, ${105}_{\mathrm{-}20}^{+25\mathrm{}}$, and ${30}_{\mathrm{-}6}^{+7\mathrm{}}$ fs, respectively. Spin assignments for levels at 1277 ${\mathrm{}\left(\right(5/2\mathrm{})\mathrm{}}^{+}$), 1581 ${\mathrm{}\left(\right(7/2\mathrm{})\mathrm{}}^{+}$), 1679 ${\mathrm{}\left(\right(7/2\mathrm{})\mathrm{}}^{+}$), 1953 ${\mathrm{}\left(\right(3/2\mathrm{})\mathrm{}}^{+}$,${\mathrm{}(5/2)\mathrm{}}^{+}$), 1964 ${\mathrm{}\left(\right(7/2\mathrm{})\mathrm{}}^{+}$), and 2233 ${\mathrm{}\left(\right(5/2\mathrm{})\mathrm{}}^{+}$) were made for the first time. Mixing ratios for many transitions were also calculated.

A semiclassical model is used to perform numerical simulations of the production of nuclear fragments in both proton- and heavy-ion-induced reactions. The Pauli principle is incorporated by means of a collision term, as it is in the Vlasov-Uehling-Uhlenbeck equation. The model goes beyond the Vlasov-Uehling-Uhlenbeck equation by propagating on an event-by-event basis the phase space fluctuations which develop during a nuclear reaction. Both the Coulomb and isospin-dependent interaction terms are included. For proton-induced reactions at intermediate energies, fragment production is found to be a fairly infrequent process, as is observed experimentally. Heavy-ion reactions show much greater fragment yields. For these latter reactions, we have compiled sufficiently many events so as to be able to compare the predicted fragment yields with experiment. The isotopic distribution of products, as well as their distribution in momentum space, are also examined. The events are used to generate a two-particle correlation function. Analysis of the energy-summed two-proton correlations indicates a large source region. The coordinate and phase space reaction trajectories are followed for a central collision, and preliminary evidence is found in the simulations for the onset of mechanical instability.

We consider theoretical models for central collisions of mass 30 on mass 30 at 70 MeV/nucleon, 100 MeV/nucleon, and 150 MeV/nucleon beam energy in the lab frame. A mass distribution is obtained for each case. At the lower energy the calculated mass distribution shows a fall considerably slower than $A^{\mathrm{-}2.64}$. The mass distribution is seen to be strongly dependent upon the initial phase-space distribution chosen. We compare our model with other models; we estimate Pauli corrections in various models and conclude that for σ/A<2 the corrections can be severe.

Inclusive measurements of the linear momentum transfer distribution and exclusive studies of light-charged particles as a function of linear momentum transfer have been performed for the reaction of 150-MeV ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ ions with ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$. Linear momentum transfer properties and an upper limit for the complete fusion cross section for this system were deduced from the folding angle between binary fission events and found to be consistent with data for heavier complex projectiles. The exclusive light-charged-particle data demonstrate the existence of fission following the transfer of all possible subdivisions of the ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ projectile, as well as inelastic scattering. Absorptive breakup involving ${}_{}{}^4{}_{}{}^{}\mathrm{-}_{}^2{}_{}{}^{}$H cluster structure is found to be the dominant reaction mechanism. In addition, substantial yields of energetic protons associated with full linear momentum transfer are observed in the backward hemisphere. However, the temperature inferred from these spectra is nearly three times as large as that for a fully equilibrated compound nucleus, suggesting a nonequilibrium source for these particles.

We have measured the spectra and angular distribution of neutrons emitted in coincidence with fission fragments in the following reactions: ${}_{}{}^{16}{}_{}{}^{}$O${+\mathrm{}}^{142}$Nd ($E_{\mathrm{beam}=207\mathrm{}}$ MeV), ${}_{}{}^{24}{}_{}{}^{}\mathrm{Ba}$ (180 MeV), ${}_{}{}^{32}{}_{}{}^{}\mathrm{Te}$ (180 MeV), and ${}_{}{}^{50}{}_{}{}^{}\mathrm{Pd}$ (216 MeV). We decompose neutron emission into components resulting from nonequilibrium emission, emission from the compound system, and emission from the fission fragments. We find that statistical model calculations tend to underestimate the number of neutrons evaporated prior to fission. Incorporating the effects of (1) the finite time until equilibrium fission probability is attained at the saddle point, (2) correction to the Bohr-Wheeler formalism due to nuclear viscosity, and (3) neutron emission during the descent from saddle to scission, improves the agreement with the experimental data. The value of the reduced nuclear dissipation coefficient β that is consistent with our data is approximately 6×${10}^{21}$ ${\mathrm{s}}^{\mathrm{-}1}$, within the framework of the model we have used.

The partial production cross sections for reaction residues following the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ fusion have been measured at $E_{\mathrm{c}.\mathrm{m}.\mathrm{}=8.0\mathrm{}–}$13.8 MeV through γ-ray spectroscopy. The Doppler-shift attenuation method in conjunction with a ${\mathrm{Ta}}_2$${\mathrm{O}}_5$ target and Ge(Li) detector was used to obtain accurate intensities of characteristic γ rays. The results are compared with those of recent experiments.

Coupled-channels calculations are carried out for the series of ${}_{}{}^{28}{}_{}{}^{}$30Si${+\mathit{}}^{58}$6264Ni fusion reactions. The low-lying excitations of the projectile and target nuclei are taken into account within the rotational and vibrational models, respectively. The effects of one- and two-nucleon transfer reactions are included in the calculations using approximate methods. A good overall agreement with the data is obtained. The fusion cross sections apparently reflect changes in the radii of the nickel isotopes suggested by Hartree-Fock calculations.

The distribution of the total energy and multiplicity of gamma rays feeding the yrast transitions has been measured for ${}_{}{}^{158}{}_{}{}^{}$,159Er, ${}_{}{}^{130}{}_{}{}^{}\mathrm{Ce}$, and ${}_{}{}^{116}{}_{}{}^{}$,117Te, which are produced in several heavy-ion fusion reactions. The observed shape of the distribution feeding discrete yrast states varies with the spin of the yrast transition. However, the differences are small, especially for heavier-ion induced reactions.

Momentum distributions of projectilelike fragments produced in the interaction of 15, 25, and 35 MeV/nucleon ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ beams on targets of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ti}$, and ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ have been measured. Widths and centroids of the quasielastic component of the distributions have been extracted for fragments ranging from ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ to ${}_{}{}^{13}{}_{}{}^{}\mathrm{N}$. The widths are compared with published data and several theoretical predictions. The Friedman model correctly predicts the charge and isotope dependence of the widths at the highest beam energy. At 15 MeV/nucleon some deviations from the trend of the published data suggest the possibility of a different reaction mechanism for the projectile-target combinations studied in the present work.

The decay properties of ${}_{}{}^{150}{}_{}{}^{}\mathrm{Tm}$ and ${}_{}{}^{150}{}_{}{}^{}\mathrm{Er}$ (produced in ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ bombardments of ${}_{}{}^{96}{}_{}{}^{}\mathrm{Ru}$) were investigated following on-line mass separation. The half-life of ${}_{}{}^{150}{}_{}{}^{}\mathrm{Tm}$ was measured to be 2.2±0.2 s rather than the value of 3.5 s available in the literature. Based on its decay characteristics, we suggest that this high-spin ${}_{}{}^{150}{}_{}{}^{}\mathrm{Tm}$ isomer has a spin assignment of $6^{\mathrm{-}}$. Among the ${}_{}{}^{150}{}_{}{}^{}\mathrm{Er}$ states fed by this $6^{\mathrm{-}}$ isomer is the yrast $4^{+}$ level (2294.8 keV) which up to now has been observed in neither β-decay nor in-beam γ-ray studies. New transitions observed in ${}_{}{}^{150}{}_{}{}^{}\mathrm{Er}$ decay establish several previously unknown levels in ${}_{}{}^{150}{}_{}{}^{}\mathrm{Ho}$. While the additional γ rays reduce from 100% to 96% the feeding to the 476-keV state in ${}_{}{}^{150}{}_{}{}^{}\mathrm{Ho}$ known earlier, the corresponding logft value is calculated to be 3.6, indicating that this is an allowed, $0^{+}$→$1^{+}$, beta transition. Photon intensities obtained for γ rays following the decay of the ${}_{}{}^{150}{}_{}{}^{}\mathrm{Ho}$ low-spin isomer resolve inconsistent values measured in two previous investigations.

Using the strong selectivity of the A(p,${\pi }^{\mathrm{-}}$)A+1 reaction for population of high-spin, two-particle one-hole final states, we have located and identified several candidates for high-spin states in the sd-shell nuclei ${}_{}{}^{20}{}_{}{}^{}\mathrm{Na}$, ${}_{}{}^{24}{}_{}{}^{}\mathrm{Al}$, ${}_{}{}^{26}{}_{}{}^{}\mathrm{Si}$, ${}_{}{}^{28}{}_{}{}^{}\mathrm{P}$, ${}_{}{}^{30}{}_{}{}^{}\mathrm{S}$, and ${}_{}{}^{31}{}_{}{}^{}\mathrm{S}$. The spin assignments are based on both the strong population of the states and the stretched-state signature of the analyzing power angular distributions.

A recently proposed phenomenological version of the quasi-deuteron mechanism for pion absorption is applied to low energy pions in flight. We analyze the 60 MeV high resolution data of the reaction ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(${\pi }^{+}$, pp${)}^{14}$N. The distorted wave calculations are successful for the transition to the 3.9 MeV $1^{+}$ state, but fail to explain triple differential cross sections for the transition to the ground state. The strongly anisotropic recoil angle distributions for both states are well accounted for by distortion and polarization effects, the latter being characteristic for transitions with L≠0. Predictions for $2^{+}$ and $3^{+}$ states are given which should allow us to verify our tentative explanation of the recoil angle dependence.

Solid state nuclear track detectors having different detection thresholds have been employed to study the fission fragments and the light charged particles emitted in the interaction of 80 and 100 MeV ${\pi }^{\pm }$ with targets of ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{U}$, ${}_{}{}^{\mathrm{nat}}{}_{}{}^{}\mathrm{Pb}$, ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$, and ${}_{}{}^{164}{}_{}{}^{}\mathrm{Ho}$. Cross sections for the production of correlated fission fragments (and other heavy charged particles) and the unpaired single charged particles were obtained in different Z and Z/β domains. Energies and masses of the reaction products are estimated. Angular correlations of the reaction products have also been obtained. A large fraction of protons and (to a lesser extent) alpha particles are found to be emitted in these interactions. It has been found that distributions of the fission fragments are only slightly anisotropic and that their mass distributions are wider than those obtained for nucleon-induced fission having similar excitation energies. The results have been compared with the scanty data available on the subject and with systems having comparable excitation energies.

A general parametrization which enables us to construct all possible approximations to the bremsstrahlung amplitude is applied to explore generalizations of existing soft-photon approximations. We establish the existence of theoretical ambiguity in defining the soft-photon approximations and we show how the bremsstrahlung cross section calculated from a soft-photon amplitude depends on the parameters. We also show that if the bremsstrahlung spectrum exhibits resonant structure, then the position of this structure $K_{\gamma }$ and its width ${\Gamma }_{\gamma }$ can be predicted by either performing the detailed bremsstrahlung calculation or using two simple formulas which relate $K_{\gamma }$ and ${\Gamma }_{\gamma }$ directly to the resonant energy $E_R$ and the width ${\Gamma }_{\mathrm{el}}$ of the resonant structure observed in the elastic scattering cross sections. This new information about $K_{\gamma }$ and ${\Gamma }_{\gamma }$ can be used to study the validity of any bremsstrahlung amplitude.

All approximations have been divided into classes, and the following approximations have been systematically studied: (i) the one-energy–one-angle approximation, which is the generalized Low’s approximation, and (ii) the two-energy–one-angle approximation, which is the generalized Feshbach-Yennie approximation. We find that all soft-photon amplitudes in the one-energy–one-angle approximation fail to adequately describe the proton-carbon bremsstrahlung (${\mathrm{p}}^{12}$Cγ) data near the 1.7-MeV resonance. These amplitudes predict the values of $K_{\gamma }$ and ${\Gamma }_{\gamma }$ which do not agree with the experimental ones. Although the problem comes from both the leading term and the second term of the amplitudes, the major difficulty lies in the derivatives of the elastic scattering amplitudes in the second term.

Our study also shows that the limited existing data (which are available only in the soft-photon region, K<200 keV) can be described by many soft-photon amplitudes in the two-energy–one-angle approximation. Since these amplitudes in the two-energy–one-angle approximation predict quite different resonant structure with different values of $K_{\gamma }$ and ${\Gamma }_{\gamma }$ at higher photon energies (200 keV<K<600 keV), a new ${\mathrm{p}}^{12}$Cγ experiment is suggested to test these amplitudes so that the best one can be selected.

The effect of the coupling to the πd channel on the intermediate energy NN scattering is studied using the recent NN→NN and NN→πd partial wave analyses as well as the coupled NN→πNN theory. Contrary to some recent claims, it is found that this coupling is important in the ${}_{}{}^1{}_{}{}^{}\mathrm{D}_2^{}{}_{}{}^{}$ and ${}_{}{}^3{}_{}{}^{}\mathrm{F}_3^{}{}_{}{}^{}$ partial waves in which the intermediate NΔ configuration dominates.

$0^{+}$→$0^{\mathrm{-}}$ transitions by medium energy protons are studied in a relativistic impulse approximation treatment. We explicitly show the appearance of nonzero values for some spin observables, e.g., the analyzing power, which vanish in an equivalent nonrelativistic treatment. We compare our calculation with experiment and find qualitative agreement.

We formulate a microscopic relativistic treatment of nucleon-nucleus inelastic scattering in a distorted wave impulse approximation. The interaction is taken from a Lorentz invariant formulation with explicit direct and exchange terms constrained by fitting to experimental NN amplitudes. This procedure allows us to apply the theory in the lower range of intermediate energies (100–400 MeV) where exchange effects are likely to be important. Application to inelastic scattering uses this interaction for both the distorting potentials and the transition interaction. Effects of explicit exchange are studied and a preliminary analysis of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(p,p’) data is presented.

Statistical and quantum dynamical expansion calculations for finite and hot quantum drops are performed. Quantum dynamical evolution trajectories are calculated and compared with static equation of state calculations. Density distributions are studied and evidence for volume dependent multifragmentation processes is obtained for most breakup temperatures. The breakup trajectories in the T,ρ plane fluctuate below the critical values of the equation of state results. Small as well as large fragments are found in U-shape spectra. At temperatures above the breakup temperature the quantum drops vaporize and at temperatures below the breakup temperature the hot drops evaporate some nucleons. For averaged initial densities of the order of equilibrium density, matter does not fragment near the critical point. Thus, it appears unlikely that the multifragmentation phenomenon can be used to study the isothermal critical region of liquid-vapor phase transitions.

We investigate why and under what conditions y scaling occurs in inclusive scattering for large, but nonasymptotic q. We explore an exactly solvable model with a particle bound to an inert core, and study for it also the plane wave, Born, West, and eikonal approximations. For all, a function related to the approximate response manifestly scales in some scaling variable y. We then consider similar functions for the exact response and study the approach to the scaling limit for q→∞. Definite conclusions are reached as to quality, origin, and preferred scaling variables.