UNT Theses and Dissertations - 11 Matching Results

Search Results

Results: 1 - 11
open access

Carbon K-Shell X-Ray and Auger-Electron Cross Sections and Fluorescence Yields for Selected Molecular Gases by 0.6 To 2 .0 MeV Proton Impact

Description: Absolute K-shell x-ray cross sections and Auger-electron cross sections are measured for carbon for 0.6 to 2.0 MeV proton incident on CH₄, n-C₄H₁₀ (n-Butane), i-C₄H₁₀ (isobutane), C₆H₆ (Benzene), C₂H₂ (Acetylene), CO and CO₂. Carbon K-shell fluorescence yields are calculated from the measurements of x-ray and Auger-electron cross sections. X-ray cross sections are measured using a variable geometry end window proportional counter. An alternate method is described for the measurement of the tran… more
Date: August 1986
Creator: Bhalla, Raj P. (Raj Pal), 1948
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Coherent Resonant Interaction and Harmonic Generation in Atomic Vapors

Description: This work examines the use of higher order multiphoton resonances in higher harmonic generation together with judicious exploitation of coherent interaction properties to achieve efficient harmonic generation. A detailed experimental study on third harmonic generation in two photon resonant coherent interaction and a theoretical study on four photon resonant coherent interaction have been conducted. Two photon resonant coheren propagation in lithium vapor (2S-4S and 2S-3D interaction) has been … more
Date: August 1987
Creator: Mukherjee, Nandini
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Degenerate Four Wave Mixing of Short and Ultrashort Light Pulses

Description: This dissertation presents experimental and theoretical studies of transient degenerate four wave mixing (DFWM) in organic dyes. Chapter 1 is an introduction to DFWM. Chapter 2 describes DFWM experiments that were performed in the gain medium of a dye laser. Chapter 3 presents the theory of DFWM of short pulses in three level saturable media. Chapter 4 presents DFWM experiments of femtosecond pulses in the saturable absorber of a passively modelocked ring dye laser. Chapter 5 presents the theor… more
Date: August 1984
Creator: McMichael, Ian C. (Ian Charles)
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Field Dependence of Optical Properties in Quantum Well Heterostructures Within the Wentzel, Kramers, and Brillouin Approximation

Description: This dissertation is a theoretical treatment of the electric field dependence of optical properties such as Quantum Confined Stark (QCS) shifts, Photoluminescence Quenching (PLQ), and Excitonic Mixing in quantum well heterostructures. The reduced spatial dimensionality in heterostructures greatly enhances these optical properties, more than in three dimensional semiconductors. Charge presence in the quantum well from doping causes the potential to bend and deviate from the ideal square well pot… more
Date: August 1989
Creator: Wallace, Andrew B.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Nonlinear Absorption Initiated Laser-Induced Damage in [Gamma]-Irradiated Fused Silica, Fluorozirconate Glass and Cubic Zirconia

Description: The contributions of nonlinear absorption processes to laser-induced damage of three selected groups of transparent dielectrics were investigated. The studied materials were irradiated and non-irradiated fused silica, doped and undoped fluorozirconate glass and cubic zirconia stabilized with yttria. The laser-induced damage thresholds, prebreakdown transmission, and nonlinear absorption processes were studied for several specimens of each group. Experimental measurements were performed at wavel… more
Date: August 1988
Creator: Mansour, Nastaran
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Nonlinear Absorption Techniques and Measurements in Semiconductors

Description: We have conducted a detailed experimental and theoretical study of nonlinear absorption in semiconductors. Experimental measurements were made on a variety of materials at wavelengths of 1.06 and 0.53 microns using a picosecond Nd:YAG laser. Both two- and three-photon processes were investigated. Values of nonlinear absorption coefficients extracted from these measurements show excellent agreement with recent theory and scaling rules. Our theoretical investigation has been carried out for two-,… more
Date: August 1985
Creator: Woodall, Milton Andrew
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Phase Transition Studies in Polar and Nonpolar Liquids at Microwave Frequencies

Description: A resonant microwave cavity technique was employed to study the dielectric behavior of some polar and non-polar liquids near the phase transition temperatures at microwave frequencies of 7.2, 9.2 and 10.1 GHz. The Slater perturbation equations for a resonant microwave cavity are briefly discussed to show that the above technique can be used to determine both the real and imaginary parts of dielectric response. Abrupt changes in dielectric response were observed near the phase transition tempera… more
Date: August 1980
Creator: Dahiya, Jai N. (Jai Narain)
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

The Rotational Spectra of Propyne in the Ground, V₁₀=1, V₁₀=2, and V₉=1 Vibrational States

Description: The problem of a vibrating-rotating polyatomic molecule is treated, with emphasis given to the case of molecules with C_3v symmetry. It is shown that several of the gross features of the rotational spectra of polyatomic molecules in excited vibrational states can be predicted by group theoretical considerations. Expressions for the rotational transition frequencies of molecules of C_3v symmetry in the ground vibrational state, singly excited degenerate vibrational states, and doubly excited deg… more
Date: August 1985
Creator: Ware, John Matthew
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

L-shell X-ray production cross sections of ₂₉Cu, ₃₂Ge, ₃₇Rb, ₃₈Sr, and ₃₉Y and M-shell X-ray production cross sections of ₇₉Au, ₈₂Pb, ₈₃Bi, ₉₀Th, and ₉₂U by 70-200 keV protons

Description: L-shell x-ray production cross sections have been measured for thin targets of 29Cu, 32Ge, 37Rb, 38Sr, and 39Y. M-shell x-ray production cross sections have been measured for thin targets of 79Au, 82Pb, 83Bi, 90Th, and 92U. All targets were irradiated with a beam of H+ ions with energies in a range from 70 to 200 keV. Experimental cross sections are compared to other measurements at higher energies and to first Born (Plane Wave Born Approximation for direct ionization and Oppenheimer-Brinkman-K… more
Date: August 1989
Creator: Gressett, David
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

The Size Effect on the Galvanomagnetic Properties of a Semiconductor

Description: A theory is developed to explain the dependence of carrier transport in a thin semiconducting film on film thickness, magnetic field strength, and the dominant bulk scattering mechanism. This theory is based on the solution of the linearized Boltzmann equation in relaxation time form. The semiconductor is assumed to be bounded and nondegenerate with spherical energy surfaces and a scalar effective mass, It is also assumed to be flat banded with totally diffuse scattering at the surface. Classic… more
Date: August 1980
Creator: Smith, V. Devon (Vernon Devon)
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Two Photon Resonant Picosecond Pulse Propagation in Lithium Vapor

Description: The work of this dissertation has been to prove that the coherence of multiphoton excitation can be studied by an appropriately phased and time delayed sequence of pulses. An application of this fundamental study of coherence has been made for the enhancement of third harmonic generation. The coherent recovery of the energy lost to the two photon absorption process enalled a larger propagation distance for the fundamental than in an interaction which is incoherent or coherent, but not using a … more
Date: August 1987
Creator: Mukherjee, Anadi
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
Back to Top of Screen