The strength distributions of hexadecapole transitions have been measured for the closed-shell nuclei of ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{50}{}_{}{}^{}\mathrm{Ti}$, ${}_{}{}^{52}{}_{}{}^{}\mathrm{Cr}$, ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ by using (p,p’) reactions at $E_p$=65 MeV. The peak-by-peak analysis revealed the distribution for the excitation energy up to around 10 MeV. In ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$, the strength is distributed into two groups. One is the well-known first $4^{+}$ state which exhausts an energy-weighted sum-rule fraction of 8.4%. The other is a bump consisting of clustering L=4 states with a total fraction of 11.2%. The structure of the bump is much the same as those of low-energy octupole resonance, suggesting the existence of a resonance-like structure of hexadecapole strength. In an analysis using a cumulative sum of the strength, a bump of a similar kind is recognized in each nucleus examined. These bumps exhaust 3–11% of the E4 energy-weighted sum rule and the centroids are situated at $E_x$=4–9 MeV.

Differential cross section and analyzing power angular distributions have been obtained for the ${}_{}{}^{87}{}_{}{}^{}(\mathit{p}\to$,d${)}^{86}$Sr reaction in two measurements using different magnetic spectrometers at incident proton energies of 94.2 and 91.8 MeV. Typical energy resolutions of 70 and 40 keV, respectively, were achieved. Optical-model parameters were obtained by fitting the elastic scattering data measured to laboratory angles of 90° for protons at 94.2 MeV and to 120° for deuterons at 88.0 MeV. Standard exact finite range distorted-wave Born approximation calculations using these optical-model parameters failed to describe the experimental data, while the adiabatic approximation improved the description to some extent. Orbital and total angular momenta, l and j, of the picked-up neutron were extracted from the angular distributions of the differential cross section and analyzing power for all the residual states observed. The rms radius of the 1$g_{9/2}$ neutron orbital, obtained from magnetic electron scattering, was used in the extraction of strength for this orbital, while rms radii from Hartree-Fock calculations were used for the 2$p_{1/2}$, 2$p_{3/2}$, 1$f_{5/2}$, and 1$f_{7/2}$ orbitals. The observed 1$g_{9/2}$ strength, spread over 20 states up to 5.4-MeV excitation, indicates a depletion of about 43% compared to simple shell-model expectations. Similarly, the observed 1$f_{5/2}$ strength, spread over 17 states, indicates a depletion of about 32%. The weighted summed spectroscopic strength for the 1$g_{9/2}$ orbital, deduced from the present study, is lower than that obtained from magnetic electron scattering.

A model for statistical multistep direct and multistep compound reactions is presented. It predicts (double-differential) neutron and proton spectra including equilibrium, preequilibrium, direct (collective and noncollective) as well as multiple particle emission processes. Calculations for nucleon-induced reactions have been performed for about 30 nuclei at incident energies between 5 and 26 MeV without any parameter fit.

A satisfactory analysis of the physics of straggling was first given by Landau, who approximated the electron-electron cross section for hard collisions by the Rutherford cross section. Data analysis computer codes continue to use the distribution derived by Landau to calculate the energy lost by electrons because of straggling. We have performed a study of straggling distributions incorporating Mo?ller and Bhabha cross sections to evaluate the precision of (e,e’) analyses that use the Rutherford-based Landau formula. In addition, the calculation of the $e^{+}$ straggling distribution is relevant to the analysis of experiments that have been proposed to study dispersive effects in nuclear electromagnetic processes by comparing results obtained from $e^{\mathrm{-}}$ and $e^{+}$ scattering from identical nuclei. Measuring differences in such cross sections requires a high degree of confidence in the data analysis. Since accuracies in cross sections on the order of a few percent are required, any differences in energy-loss mechanisms of the same order must be taken into account. In this work, we study the differences in positron and electron straggling at energies of present-day interest.

A new geometrical representation for the state of polarization of spin-one particles is suggested which in the limit of mass zero reduces to the well-known Poincare sphere representation for light. A careful consideration of the bounds on the polarization parameters of spin-one resonances produced in parity-conserving processes is also discussed as yet another particular case.

We have developed a technique for deducing the average primary excitation energy and mass of a hot nuclear system using the average energies and multiplicities of the decay products. Monte Carlo simulations show that we can account for all of the initial energy and mass in heavy-ion fusion reactions. For data from the reaction ${}_{}{}^{20}{}_{}{}^{}$Ne${+}^{27}$Al at 19.2 MeV/nucleon we find that the composite system formed after preequilibrium emission consists of 42.4 nucleons, on average, at an excitation energy of 4 MeV/nucleon. Similar data for Si+Si imply that the excitation energy per nucleon of these incompletely fused systems saturates near 3 MeV/nucleon with increasing beam energy.

The classical dynamics of two heavy, deformed ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ nuclei is studied for the nuclear alignment effects at incident energies below and above the Coulomb barrier. In addition to the internuclear potential, frictional forces are also included in the classical equations of motion. The frictional forces are shown to be very important for estimating the orientation probability at the distance of closest approach.

The δ-electron spectra from dissipative reactions of the collision systems Pb+U and Pb+Pb show the influence of large nuclear contact with increasing Q value. An analysis independent of nuclear models allows us to determine the trajectories of the collisions. Comparison with the reaction model of Schmidt, Toneev, and Wolschin and the one of Feldmeier is made. The applicability of δ-electron spectroscopy in lighter systems is discussed.

A hot nucleus is unstable if its temperature exceeds a certain limiting value due to the Coulomb repulsion between its protons. This instability is investigated using a finite-temperature generalization of the liquid-drop model. For this purpose an equation of state for asymmetric nuclear matter derived in a previous work with the use of a Skyrme-type effective interaction is generalized to the case of a density-dependent effective mass. Standard parametrizations of the Skyrme interaction are used to study the properties of a hot ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ nucleus immersed in a uniform vapor. Good agreement is achieved between the present model and the results of finite-temperature Hartree-Fock calculations only if the Coulomb interaction between the vapor and the drop is properly taken into account. The results are seen to yield valuable information on the temperature dependence of the surface tension of hot nuclei.

The dependence of various measurable properties of heavy-ion collisions is calculated with the Boltzmann equation, in an attempt to find the best observables to determine the impact parameter in a collision. The observables considered are multiplicity of fast nucleons longitudinal momentum transfer, angular momentum transfer, projectile mass loss, and projectile energy loss. Systems studied in detail include the ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$${+}^{154}$Sm reaction at E/A=35 MeV, the ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$${+}^{197}$Au reaction at E/A=60 MeV, and the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{197}$Au reaction at E/A=90 MeV where some experiments have been performed with reaction filters. The energy and impact parameter dependence of nucleon multiplicity distributions have also been studied for the mass symmetric ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$${+}^{40}$Ar and asymmetric ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{197}$Au systems at energies ranging from E/A=35 to 400 MeV. These calculations suggest that the mean multiplicity of fast nucleons and the linear momentum transferred to the target residue are relatively insensitive to the impact parameter at small impact parameters and incident energies below E/A≤60 MeV. These nucleon multiplicity distributions become more sensitive to impact parameters with increasing incident energy and may provide rather accurate impact parameter information for incident energies as large as E/A≊90 MeV.

Energy and angular distributions of neutrons emitted in coincidence with projectile-like fragments from the damped reaction ${}_{}{}^{139}{}_{}{}^{}\mathrm{La}$${+}^{40}$Ar at a bombarding energy of 600 MeV have been measured. Components corresponding to sequential emission from two fully accelerated reaction fragments as well as preequilibrium neutron emission have been separated as a function of energy loss and fragment atomic number. The deduced division of total excitation energy between the reaction partners is very well described by the one-body nucleon-exchange model for all energy losses. The data provide no evidence for correlations between the excitation energy division and the measured projectile-like fragment atomic number.

The Boltzmann-Uehling-Uhlenbeck and relaxation time methods are compared numerically for collisions between two ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ nuclei. Phase-space trajectories and double differential cross sections for nucleon emission are compared. Results are practically identical although the relaxation time method exhibits a slightly higher degree of stopping power.

A model for nucleus-nucleus multiplicity distributions is proposed and its relations with hadron-proton and hadron-nucleus multiplicity distributions are explored and compared with the experimental data. The values of the parameters are the same for all these processes and owe their origin to the quantum chromodynamical gluon bremsstrahlung mechanism. Some other consequences of the model are also analyzed and compared with the available experimental data.

Low-energy nucleon-nucleon phase shifts are calculated in resonating group formalism using a Dirac basis for quarks with gluon, pion, and sigma exchange quark-quark interactions. Nucleon polarization as well as quark interchange are included for the short-distance behavior. Reasonable agreement with experiment is obtained.

The methods of extraction of total cross sections are reviewed. The particular application to the ${\mathrm{K}}^{+}$ nucleus case is considered. Because of the reliability of basic calculations of ${\mathrm{K}}^{+}$ nuclear corrections, the total cross section can be extracted with very high reliability. The specific corrections have been calculated for ${}_{}{}^2{}_{}{}^{}\mathrm{H}$, ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, and ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ for momenta in the range 550–800 MeV/c.

The random-phase-approximation description of nuclear excitations is applied to the calculation of inelastic scattering of 500 MeV protons from ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ at 500 MeV. The calculations are based on a relativistic mean-field theory applied in a consistent manner for bound and continuum states in a distorted-wave impulse approximation. Differences in spin observables between our random-phase-approximation treatment and collective model treatments are traceable to ΔS=1 terms included in the random-phase approximation. Agreement with data is somewhat better using the random-phase-approximation approach.

Existing data for the $0_2^{+}$ state in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ at 50 and 67.5 MeV are compared with coupled channels calculations. Calculations are done with a realistic potential which includes the Lorentz-Lorenz-Ericson-Ericson p-wave correction and terms second order in the nuclear density. These are compared to results obtained using a phenomenological Kisslinger potential to investigate the sensitivity to the details of the πA interaction. The suppression of the forward angle cross sections by the Lorentz-Lorenz-Ericson-Ericson effect is insufficient to bring the direct transition into agreement at both energies. The interference between the one- and two-step excitation mechanisms is required to reproduce the forward angle data. The dependence of the cross section on the choice of monopole transition density is examined.

We analyze the new accurate data on the vector analyzing power and the experimental results on tensor polarization observables for πd elastic scattering, and simultaneously investigate the ΔN interaction of short range. Using as a basis the πd amplitudes obtained by Garcilazo, we show that the data are well described in terms of ΔN interaction in the ${}_{}{}^5{}_{}{}^{}\mathrm{S}_2^{}{}_{}{}^{}$, ${}_{}{}^5{}_{}{}^{}\mathrm{P}_3^{}{}_{}{}^{}$, and ${}_{}{}^3{}_{}{}^{}\mathrm{S}_1^{}{}_{}{}^{}$ states, which reflect themselves in small and regular changes in the ${}_{}{}^3{}_{}{}^{}\mathrm{P}_2^{}{}_{}{}^{}$, ${}_{}{}^3{}_{}{}^{}\mathrm{D}_3^{}{}_{}{}^{}$, and ${}_{}{}^3{}_{}{}^{}\mathrm{P}_1^{}{}_{}{}^{}$ πd partial wave amplitudes.

Nuclear orientation of ${}_{}{}^{160}{}_{}{}^{}\mathrm{Tb}$ in a Tb single crystal has been carried out in order to obtain accurate values of multipole mixing ratios for 22 transitions in ${}_{}{}^{160}{}_{}{}^{}\mathrm{Dy}$. The experimental aspects are described in some detail as they form the basis for obtaining high quality data. Three different methods were used to extract the mixing ratios, and they are shown to agree very well. Our results for both E1/M2 and E2/M1 transitions are compared to other measurements. The signs and magnitude of the E1/M2 mixing ratios cannot be explained on the basis of Coriolis mixing of the K=0, 1, and 2 bands. Comparison of our results for the 299, 1178, and 1272 keV transitions with those from γ-γ directional correlation measurements indicate that some E3 admixture may be present in these transitions. The mixing ratios we obtained for the E2/M1 transitions are in reasonably good agreement with the predictions of the interacting-boson-approximation-1 model.

Starting from shell structure and nuclear effective interaction among nucleons, a microscopic model investigating intruder states and shape coexistence in even-even nuclei near the closed shell has been established. Two methods of finding wave functions are also introduced. We present configuration mixing calculations within the model on ${}_{}{}^{112}{}_{}{}^{}$,114Cd, ${}_{}{}^{114}{}_{}{}^{}$,116Sn, and ${}_{}{}^{116}{}_{}{}^{}$,118,120Te isotopes. Both methods give a good description of low-lying levels (energy spectra and E2 transition properties). We find that the mixing is not strong in these cases. We also point out the important roles of np interaction and np correlations in treating intruder states and shape coexistence.