Latest content added for Digital Library Partner: UNT Librarieshttps://digital.library.unt.edu/explore/partners/UNT/browse/?fq=str_degree_discipline:Physics&fq=untl_collection:UNTETD&fq=str_degree_level:Master's2017-10-09T11:44:47-05:00UNT LibrariesThis is a custom feed for browsing Digital Library Partner: UNT LibrariesDynamic Screening via Intense Laser Radiation and Its Effects on Bulk and Surface Plasma Dispersion Relations2017-10-09T11:44:47-05:00https://digital.library.unt.edu/ark:/67531/metadc1011758/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc1011758/"><img alt="Dynamic Screening via Intense Laser Radiation and Its Effects on Bulk and Surface Plasma Dispersion Relations" title="Dynamic Screening via Intense Laser Radiation and Its Effects on Bulk and Surface Plasma Dispersion Relations" src="https://digital.library.unt.edu/ark:/67531/metadc1011758/small/"/></a></p><p>Recent experimentation with excitation of surface plasmons on a gold film in the Kretschmann configuration have shown what appears to be a superconductive effect. Researchers claimed to see the existence of electron pairing during scattering as well as magnetic field repulsion while twisting the polarization of the laser. In an attempt to explain this, they pointed to a combination of electron-electron scattering in external fields as well as dynamic screening via intense laser radiation. This paper expands upon the latter, taking a look at the properties of a dynamic polarization function, its effects on bulk and surface plasmon dispersion relations, and its various consequences.</p>Relaxation Time Measurements for Collision Processes in the Surface Layers of Conductors and Semiconductors Near 10 Ghz2015-06-24T09:39:17-05:00https://digital.library.unt.edu/ark:/67531/metadc663566/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc663566/"><img alt="Relaxation Time Measurements for Collision Processes in the Surface Layers of Conductors and Semiconductors Near 10 Ghz" title="Relaxation Time Measurements for Collision Processes in the Surface Layers of Conductors and Semiconductors Near 10 Ghz" src="https://digital.library.unt.edu/ark:/67531/metadc663566/small/"/></a></p><p>This thesis represents one phase of a joint effort of research on the properties of liquids and solids. This work is concerned primarily with the microwave properties of solids. In this investigation the properties exhibited by conductor and semiconductor materials when they are subjected to electromagnetic radiation of microwave frequency are studied. The method utilized in this experiment is the perturbation of a resonant cavity produced by introduction of a cylindrically shaped sample into it.</p>Microwave Line Widths of the Asymmetric Top Formic Acid Molecule2015-06-24T09:39:17-05:00https://digital.library.unt.edu/ark:/67531/metadc663604/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc663604/"><img alt="Microwave Line Widths of the Asymmetric Top Formic Acid Molecule" title="Microwave Line Widths of the Asymmetric Top Formic Acid Molecule" src="https://digital.library.unt.edu/ark:/67531/metadc663604/small/"/></a></p><p>This work consisted of an experimental investigation of the formic acid (HCOOH) molecule's rotational spectrum. Measurements of line widths were obtained for J = 5, 12, 13, 19, and 20 for a pressure range from 1 to 10 microns. A linear behavior between Av and p was observed as predicted by theory. The line width parameter Avp was observed to depend on the quantum number J. Hard sphere collision diameters b1 were calculated using the obtained AvP values. These deduced hard sphere values were found to be larger than the physical size of the molecule. This result was found to be in general agreement with other investigation in which long range forces (dipole-dipole) dominate.</p>Effects of Discharge Tube Geometry on Plasma Ion Oscillations2015-06-24T09:39:17-05:00https://digital.library.unt.edu/ark:/67531/metadc663636/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc663636/"><img alt="Effects of Discharge Tube Geometry on Plasma Ion Oscillations" title="Effects of Discharge Tube Geometry on Plasma Ion Oscillations" src="https://digital.library.unt.edu/ark:/67531/metadc663636/small/"/></a></p><p>This study considers the effect, on plasma ion oscillations, of various lengths of discharge tubes as well as various cross sections of discharge tubes. Four different gases were used in generating the plasma. Gas pressure and discharge voltage and current were varied to obtain a large number of signals.
A historical survey is given to familiarize the reader with the field. The experimental equipment and procedure used in obtaining data is given. An analysis of the data obtained is presented along with possible explanations for the observed phenomena. Suggestions for future study are made.</p>The Classical Limit of Quantum Mechanics2015-05-10T06:16:59-05:00https://digital.library.unt.edu/ark:/67531/metadc504591/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc504591/"><img alt="The Classical Limit of Quantum Mechanics" title="The Classical Limit of Quantum Mechanics" src="https://digital.library.unt.edu/ark:/67531/metadc504591/small/"/></a></p><p>The Feynman path integral formulation of quantum mechanics is a path integral representation for a propagator or probability amplitude in going between two points in space-time. The wave function is expressed in terms of an integral equation from which the Schrodinger equation can be derived. On taking the limit h — 0, the method of stationary phase can be applied and Newton's second law of motion is obtained. Also, the condition the phase vanishes leads to the Hamilton - Jacobi equation. The secondary objective of this paper is to study ways of relating quantum mechanics and classical mechanics. The Ehrenfest theorem is applied to a particle in an electromagnetic field. Expressions are found which are the hermitian Lorentz force operator, the hermitian torque operator, and the hermitian power operator.</p>Automatic Frequency Control of Microwave Radiation Sources2015-05-10T06:16:59-05:00https://digital.library.unt.edu/ark:/67531/metadc504304/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc504304/"><img alt="Automatic Frequency Control of Microwave Radiation Sources" title="Automatic Frequency Control of Microwave Radiation Sources" src="https://digital.library.unt.edu/ark:/67531/metadc504304/small/"/></a></p><p>Resonant cavity controlled klystron frequency stabilization circuits and quartz-crystal oscillator frequency stabilization circuits were investigated for reflex klystrons operating at frequencies in the X-band range. The crystal oscillator circuit employed achieved better than 2 parts in 10 in frequency stability. A test of the functional properties of the frequency standard was made using the Stark effect in molecules.</p>Test of Gauge Invariance: Charged Harmonic Oscillator in an Electromagnetic Field2015-05-10T06:16:59-05:00https://digital.library.unt.edu/ark:/67531/metadc504158/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc504158/"><img alt="Test of Gauge Invariance: Charged Harmonic Oscillator in an Electromagnetic Field" title="Test of Gauge Invariance: Charged Harmonic Oscillator in an Electromagnetic Field" src="https://digital.library.unt.edu/ark:/67531/metadc504158/small/"/></a></p><p>The gauge-invariant formulation of quantum mechanics is compared to the conventional approach for the case of a one-dimensional charged harmonic oscillator in an electromagnetic field in the electric dipole approximation. The probability of finding the oscillator in the ground state or excited states as a function of time is calculated, and the two approaches give different results. On the basis of gauge invariance, the gauge-invariant formulation of quantum mechanics gives the correct probability, while the conventional approach is incorrect for this problem. Therefore, expansion coefficients or a wave function cannot always be interpreted as probability amplitudes. For a physical interpretation as probability amplitudes the expansion coefficients must be gauge invariant.</p>A Technique for Increasing the Optical Strength of Single-Crystal NaCl and KCl Through Temperature Cycling2015-05-10T06:16:59-05:00https://digital.library.unt.edu/ark:/67531/metadc504009/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc504009/"><img alt="A Technique for Increasing the Optical Strength of Single-Crystal NaCl and KCl Through Temperature Cycling" title="A Technique for Increasing the Optical Strength of Single-Crystal NaCl and KCl Through Temperature Cycling" src="https://digital.library.unt.edu/ark:/67531/metadc504009/small/"/></a></p><p>This thesis relates a technique for increasing the optical strength of NaCl and KCl single-crystal samples. The 1.06-μm pulsed laser damage thresholds were increased by factors as large as 4.6 for a bulk NaCl single-crystal sample. The bulk laser damage breakdown threshold (LDBT) of the crystal was measured prior to and after heat treatment at 800*C using a Nd:YAG laser operating at 1.06 μm. Bulk and surface LDBTs were also studied on samples annealed at 400° C. These samples showed differences in damage morphology on both cleaved and polished surfaces, and the cleaved surfaces had improved damage thresholds. However, neither the polished surfaces nor the bulk showed improved threshold at the lower annealing temperature.</p>The Stopping Power of Amorphous and Channelled Silicon at All Energies as Computed with the Binary Encounter Approximation2014-03-26T09:30:20-05:00https://digital.library.unt.edu/ark:/67531/metadc279387/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc279387/"><img alt="The Stopping Power of Amorphous and Channelled Silicon at All Energies as Computed with the Binary Encounter Approximation" title="The Stopping Power of Amorphous and Channelled Silicon at All Energies as Computed with the Binary Encounter Approximation" src="https://digital.library.unt.edu/ark:/67531/metadc279387/small/"/></a></p><p>This thesis utilizes the binary encounter approximation to calculate the stopping power of protons penetrating silicon. The main goal of the research was to make predictions of the stopping power of silicon for low-energy and medium-energy channelled protons, in the hope that this will motivate experiments to test the theory developed below. In attaining this goal, different stopping power theories were compared and the binary encounter approach was applied to random (non-channelled) and high-energy channelled protons in silicon, and these results were compared with experimental data.</p>Gamma Ray Distribution from Neutron Excitation in Cesium2013-06-04T22:29:06-05:00https://digital.library.unt.edu/ark:/67531/metadc163933/<p><a href="https://digital.library.unt.edu/ark:/67531/metadc163933/"><img alt="Gamma Ray Distribution from Neutron Excitation in Cesium" title="Gamma Ray Distribution from Neutron Excitation in Cesium" src="https://digital.library.unt.edu/ark:/67531/metadc163933/small/"/></a></p><p>The purpose of this investigation was to analyze the gamma rays resulting from excitation of Cs133 by the inelastic scattering of 14 MeV neutrons and to determine the relative intensity of each gamma ray.</p>