Thesis (Ph. D.)--Florida State University, 2006. / Advisor: Jianming Cao, Florida State University, College of Arts and Sciences, Dept. of Physics. Title and description from dissertation home page (viewed June 8, 2006). Document formatted into pages; contains xiii, 111 pages. Includes bibliographical references.

Thesis (M.S.)--University of Missouri-Columbia, 2005. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (July 13, 2006) Includes bibliographical references.

Thesis (Ph.D.)--Texas Christian University, 2007. / Title from dissertation title page (viewed Jul. 5, 2007). Includes abstract. Includes bibliographical references.

Thesis (Ph. D.)--University of Sydney, 2008. / Includes graphs and tables. Title from title screen (viewed November 28, 2008) Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the School of Chemistry, Faculty of Science. Includes bibliographical references. Also available in print form.

Thesis (Ph.D.)--Boston University. / Hartree-Fock self-consistent field calculations of the Roothaan (linear combination of atomic orbitals - molecular orbital) type have been carried out on an electronic computer for LiH and Li2 using an extended basis set of Slater type atomic orbitals. Configuration interaction calculations result in a total molecular energy of 99.34% of the experimental value, and a dissociation energy of 89.33% of the experimental value in LiH. Similar calculations in Li2 result in 99.40% and 89.9%, respectively, for these two numbers. The energy of atomic Li, which enters the dissociation energy calculation, is calculated to comparable accuracy (99.42%). [TRUNCATED]

The process e+e- → Z0 → bb is studied using prompt electrons. The partial width of the Z0 boson into bb pairs is found to be 400 ± 35 ± 57 ± 3 MeV, and the forward-backward asymmetry in the reaction e+e- → Z0 → bb is found to be 0.101 ± 0.029 ± 0.011 ± 0.006. / Graduate

This thesis is primarily concerned with a description of a new apparatus for the measurement of the angular correlation of positron-electron pairs produced internally in high energy, electromagnetic transitions in light nuclei. The apparatus consists of two counter telescopes, operating in coincidence, enclosed in a steel vacuum vessel whose axis coincides with the direction of the beam of bombarding particles. Each telescope consists of a proportional counter and a plastic scintillator spectrometer operating in coincidence. Because of the light construction of the proportional counters, the telescopes have a low sensitivity to gamma rays. The scintillation counters permit the use of fast coincidence techniques and the analysis of complex spectra, the latter being the great advantage of this apparatus. One of the telescopes is fixed in position while the other can be rotated about the direction of the beam. The reliability of the apparatus was established from measurements of the angular correlation of the internal pairs from the well-known pair emitting state of 0¹⁶. Preliminary measurements of the angular correlation of the internal pairs from the 7.48 mev. level in B¹º indicate that this transition is a mixture of E1 and M1 type radiations, the El being the predominant one. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

PART 1 A new method has been used to suppress the undesirable Compton electrons ordinarily present in photoelectron spectra. As much as 90% of the Compton electron intensity was removed. This was accomplished by electronic cancellation of the individual Compton electrons. The method has been used with a thin lens type of spectrometer and has made possible the detection of new gamma rays at .391, .857 and 1.00 Mev. in Ra(B + C), at 1.01 Mev. in Ta¹⁸², and at .472 and .843 Mev. In Sb¹²⁴. No.new gamma rays were observed from Co⁶⁰. PART 2 A search for double beta decay in Sn¹²⁴ has been made using a coincidence technique particularly suited to double beta decay under the Majorana form of neutrino theory. Negative results were obtained and a lower limit of 0.3 - 0.7 x 10¹⁷ years has been set on the half-life of the process. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A wide variety of inelastic scattering and electron attachment phenomena have been studied by directing an electron beam into a gas filled chamber and by observing the results of the interaction. The use of a "monoenergetic" electron beam has permitted the relative cross sections for such processes to be examined in some detail. Three instruments were used to make the measurements, and these instruments were designed and constructed during the course of the work to be described. All three employed a 127° electrostatic electron velocity selector to filter the electron beam. An electron energy analyzer permitted the observation of inelastically scattered electrons, and a monopole or a quadrupole mass filter permitted the measurement of the relative amounts of positive or negative ionization generated by the electron beam in its interaction with the gas. The measurement of the energy dependence of the cross sections was the prime objective of the work, and much care was taken in the design of the instruments to ensure that the cross section curves were not distorted by spurious effects. The forward inelastic scattering spectra of helium and ethylene were recorded using an electron beam having an incident energy of 50 eV . The ionization efficiency curves of singly and doubly charged helium were obtained, and the results are compared with several theoretically derived expressions for electron impact threshold laws. The positive ionization efficiency curves for nitrogen and oxygen were also obtained. An examination of the dissociative capture, non-dissociative capture and ion pair processes has been made by determining the energy dependence of the cross sections for the production of the parent and/or fragment negative ions from nine molecules. Finally, the generation of zero energy electrons from inelastic scattering events has been studied by using sulfur hexafluoride as an electron scavenger in a mixture with the sample gas. The threshold electron impact spectra were obtained for six atomic and molecular species. In all cases, such measurements were carried out below and above the ionization potential of the sample. / Science, Faculty of / Chemistry, Department of / Graduate

In this thesis the problem of an electron in a crystal in the presence of a uniform magnetic field is investigated using group theory method. A group of operators [ symbol omitted ] commuting with the Hamiltonian of an electron in the presence of a uniform magnetic field and a crystal electric potential is constructed. This group is homomorphic to the group [ symbol omitted ] (a magnetic space group) of space time transformations that leave the magnetic field and the crystal electric potential invariant. The property of the subgroup [ symbol omitted ] of [ symbol omitted ] that under the above homomorphism is mapped onto the lattice [ symbol omitted ] of [ symbol omitted ] is studied in detail. It turns out the structure of [ symbol omitted ] depends on the magnitude and the orientation of the magnetic field, so that, in fact one has to deal with an infinite class of groups. In particular, it is useful to divide this infinite class of groups into two subclasses: one subclass is then referred to as corresponding to "rational" magnetic fields, the other as corresponding to "irrational" magnetic field. The group [ symbol omitted ] is a generalisation of the "magnetic translation group" recently introduced by Zak for the special case of a symmetric gauge. He also constructed "physical" irreducible representations of the "magnetic translation group" for the special case of a "rational" magnetic field. In this case a group [ symbol omitted ] always has a maximal Abelian subgroup with a finite index. (The term "physical" representation simply means a representation which can be generated by functions of spatial coordinates.) In this thesis no such restriction is introduced: the "physical" irreducible representations of [ symbol omitted ] are also constructed for the case of irrational magnetic field, in which case the index of a maximal Abelian subgroup is always infinite; the "physical" irreducible representations are then always infinite dimensional. Using a complete set of Landau functions the basis functions generating "physical" irreducible representations of [ symbol omitted ] are found for the special case when the crystal is simple cubic and the magnetic field is parallel to a lattice vector. It turns out when the field is "irrational" the basis functions are countably infinite sets of Landau functions, and the energy spectrum depends only on one of the parameters labelling the "physical" irreducible representations of [ symbol omitted ]. The problem of perturbation produced by a weak periodic potential on the Landau levels for a free electron in a magnetic field is also considered. In this connection we make plausible the validity of certain quite general selection rules for an arbitrary periodic potential. / Science, Faculty of / Physics and Astronomy, Department of / Graduate