In this dissertation, a theory of vibration-rotation (V-R) energy transfer in atom-vibrating-rotor collisions is formulated by a simple extension of the Arthurs and Dalgarno atom-rigid-rotor theory, and V-R transition probabilities, cross sections and rate constants are found from solutions to a set of coupled differential equations. The theory is tested on two near-resonant V-R energy transfer processes. First, the rate constant for the (υ=0, j=20 <– υ=1, j=15) transition in Ar-OH(A^2 Σ^+) is calculated in the infinite-order sudden approximation and in the distorted-wave approximation at 360°K. The results agree with experiment and indicate that the transition is direct and first-order. Second, cross sections for the (υ=1, j=7 <– υ=0, j=11) excitation in Li^+ -H_2(X^1 Σ_g^+) are obtained in the exponential distorted-wave approximation at 14,000°K. The calculated cross sections are larger than those of neighboring off-resonant V-R and non-V-R transitions. It is concluded that near-resonant V-R energy transfer is an important process in atom-diatom collisions.

This dissertation presents a semiclassical microscopic approach based on the Uehling-Uhlenbeck equation for studying the equilibration processes due to nucleon-nucleon collisions during the collision of two heavy ions in the low and intermediate energy domain (5-100 MeV/nucleon). The state formed in the early stages of a heavy-ion collision can be characterized by a highly excited non-equilibrium system of nucleons. Equilibration processes then take place resulting in a system for which a temperature can be defined at least locally. The single-nucleon distribution function for the nucleons during the early stage of the ion-ion collision is represented in momentum-space either by two Fermi-spheres separated by the relative momentum of the impacting ions or by a deformed Fermi-sphere. The equilibration (thermalization) of this initial distribution in momentum-space is studied by calculating the collision term as a function of time. The relaxation-times are investigated through a microscopic model that incorporates the UU collision term with the relaxation-time approximation. Relaxation-times for the equilibration are obtained as a function of density and temperature. The temperature dependence is strong at low temperatures and this is a consequence of the Fermi statistics. The mode dependence of the relaxation-times is also calculated by expanding the angular dependence of the distribution in spherical harmonics. The RTA is also tested against thermalization of the Fermi-sphere systems and is found to be reasonable. Transport coefficients for viscosity, thermal conductivity and diffusion are also calculated as well as their temperature and density dependencies. Their relation to relaxation-times are derived. The mean free path of nucleons in hot nuclear matter is also studied in the same frame of work. The numerical calculations of the collision term are an important part of this investigation. They involve five-dimensional integrations carried out using Gaussian and Simpson's numerical methods.

We calculate two-body effective interactions starting from a free nucleon-nucleon interaction and apply these interactions in shell-model calculations for no-core model spaces where all particles of the nucleus are active. The spurious center-of-mass motion is explicitly removed from the Hamiltonian. The role of the kinetic-energy operator is examined for ¹⁶O and ¹⁷O. Convergence properties of no-core model spaces are shown for ⁴He and ¹⁸O. The starting-energy dependence is removed by employing the effective Hamiltonian approach of Lee and Suzuki, and the results are applied to the deuteron. Different single-particle wavefunctions are applied to formfactor calculations for ¹⁷O in the extreme single-particle model and the results for high-momentum transfer are compared with the experimental data.

The proton-neutron Interacting-Boson Model contains both symmetric and mixed-symmetry proton-neutron boson configurations. These states of different proton-neutron symmetry can be classified in terms of an SU(2) symmetry, called F-spin. This dissertation deals with some new applications of F-spin. Even-even nuclei drawn from the proton and neutron shells 50 < Z < 82 and 82 < N < 126, respectively, are systematically classified in F-spin multiplets and their binding energies are fit with a six-parameter mass-formula. Using particle-hole symmetry conjugation, the energies of the low-lying levels of the neutron-rich nuclei are estimated and their mass excesses determined with the mass-formula. The masses of these nuclei are of interest in astrophysical processes. A novel asymptotic realization of the angular-momentum projected intrinsic-state in the generalized IBM is presented. This approach which uses the Laplace method of asymptotic expansion, is shown to be an improvement over the Gaussian method espoused by Kuyucak and Morrison. The method, herein called the 1/Λ-expansion, is used to derive analytical expressions for different quantities in the framework of the generalized IBM. Particular attention is paid to the M1 summed strength, the mean-excitation energy of the mixed symmetry 1⁺ scissor mode, and the gyromagnetic ratios of the ground-band members, for which formulas are derived. A no-free-parameter calculation is performed for the summed M1 strength and the centroid energy of ⁽¹⁴⁶⁻¹⁵⁸⁾Sm isotopes. The g factors of deformed and transitional nuclei in the rare-earth mass region are also computed. The data in all cases are found to be well reproduced, in general. A weak L dependence is predicted for the g factors, and there appears to be no need to include two-body terms in the T(M1) operator for determining the M1 strength.

Within the framework of the quantum transport theory based on the Wigner transform of the density matrix I study first in non-relativistic and subsequently in relativistic formulation a number of applications. I also develop further the recently proposed relativistic theory: the classical limit is carefully derived and the integral equations of the relativistic Wigner function derived explicitly. I show how it is possible to obtain the Schwinger like particle production rate from relativistic quantum transport equations. Noteworthy numerical results address the shape of the relativistic Wigner function of a given quantum state. Other numerical studies are primarily oriented towards the time evolution of the Wigner function--I can presently solve only the nonrelativistic case in which there is no mixing between particle production and flow phenomena: I consider numerically the fate of the muon after muon catalyzed fusion.

A general interacting boson model of clustering in nuclei is presented. The model is then specialized to the case of n identical α-clusters [U(6) (CRTIMES) U(4)] , followed by a detailed study of the SU(3) dynamical limit. Many useful formulae are derived in this limit. The general problem of coexistence and configuration mixing is discussed, and a useful SU(3) bank mixing approximation (BMA) is presented. Formulae for the case of two mixed configurations are derived. The method of calculating the matrix elements for two-nucleon transfer reactions is demonstrated, and formulae for α-decay reduced widths are given. This model is then utilized for the study of the systematic trends of the data available for actinide nuclei. Most of the results presented here are for the well-deformed even-even mass actinides with A < 242; however, some trends in going to the spherical region and to larger A are studied. Tests, based on experimental data, are presented to discriminate between different limits of this model, and between this and other models. The limit of the model presented here satisfies all of the experimental tests found, while all other competing models were found to have serious deficiencies. This phenomenological study indicates that α-clustering effects are of fundamental importance for understanding the structure and dynamics of actinide nuclei. Suggestions for future research are made, some of which are based on preliminary work that has already been done.

No description available.

A measurement of the reaction 12 C (γ,p γ') has been made with tagged photons in the range 49.47<Eγ <70.24 MeV. The relative population of a triplet of states, (7/2-,1/2+ ,5/2+ ) at Eex ~7 MeV in the residual nucleus 11B, following the reaction 12 C (γ,p) has been made by directly resolving their de--excitation γ-­ray decay to the ground state of 11B. This measurement constitutes the highest resolution ever achieved in determining the excitation function of the residual nucleus after a (γ,p) reaction (~48 keV FWHM at Eex ~7 MeV). Comparison has been made with the data of Kuzin et al., who also measured the relative populations, with a resolution of ~270 keV at Eex ~7 MeV. The 7/2-,state at 6.74 MeV has been observed to be the most strongly excited state of the triplet in agreement with Kuzin et al. Disagreement has been found for the relative strengths of the 1/2 + and 5/2 + states in the triplet. An estimation of the maximum effect of angular correlations, between the ejected proton and de-excitation γ-­ray, has been included in the analysis. This effect increases the disagreement between the 2 measurements.

This thesis describes a study of the 12 C(gamma; pie + n) reaction in the Delta resonance re­ gion using tagged photons. The experiment was accomplished using the MAMI­B c.w. electron accelerator at the Institut f¨ur Kernphysik, Mainz. Bremsstrahlung photons, created when 855 MeV electrons strike a 4 ¯m Nickel radiator, were tagged with a 2 MeV resolution using the Glasgow tagging spectrometer installed in the MAMI A2 experimental hall. The data is presented as triple and (by integrating over the pion energy) double differential cross sections. A comparison is made with Distorted Wave Impulse Approximation (DWIA) predictions generated by the code THREEDEE. It is concluded that more reliable theoretical calculations are required. In particular, a better treatment of the distortion and absorption of the outgoing particles is needed. Initial comparisons with the microscopic theory of Carrasco are attempted and the problems faced in making such a comparison are described and solutions suggested.

A prototype ASIC (EFT1) for silicon strip detector instrumentation has been designed and tested. The ASIC design contains the electronics necessary for preamplification, shaping, hit detection, and data readout control. The specific­ ation of the ASIC makes it suitable for charged particle spectroscopy applications with the implementation of multiple channels on a single chip reducing the cost compared to expensive discrete instrumentation. The ASIC contains features which have not been implemented before, or are at least unusual, on integrated instrumentation such as the ability to select two gain ranges, the use of a flat­top shaper to increase integral linearity and a current­ driven discriminator output with adjustable voltage to reduce crosstalk effects on sensitive inputs. The testing performed on the ASIC revealed errors that can be removed in further design of the chip which will be implemented using radiation­hard silicon technology.