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Electrolysis of Aluminum Solutions in a Magnetic Field (open access)

Electrolysis of Aluminum Solutions in a Magnetic Field

This investigation is an attempt to verify the original work done by George Antonoff and Anne Rowley, and to contribute specific data on the action of a magnetic field on aluminum cells. Experiments of the type they have described have been performed and an extensive set of data has been collected. It was thought that if the results of Antonoff and Rowley could be duplicated, further investigation would be warranted. However, the experiments have produced negative results. These results are described in detail in these chapters.
Date: May 1950
Creator: Wood, Charles E.
System: The UNT Digital Library
Nuclear Magnetic Resonance in Hydrated Crystals - Potassium Oxalate Monohydrate (open access)

Nuclear Magnetic Resonance in Hydrated Crystals - Potassium Oxalate Monohydrate

The problem of this study was the measurement of the proton-proton separation in the water molecule of hydration in a single crystal of potassium oxalate monohydrate.
Date: May 1962
Creator: Mason, Charley Mack
System: The UNT Digital Library
Proton Nuclear Magnetic Resonance in Mica (open access)

Proton Nuclear Magnetic Resonance in Mica

The experiments to be described here were undertaken for the purpose of determining, if possible, by NMR techniques whether or not the hydroxyl protons in mica are bound in a regular crystalline array, and, if so, whether or not the hydroxyl protons occur in reasonably isolated pairs as in waters of hydration.
Date: May 1962
Creator: Townsend, Don H.
System: The UNT Digital Library
Electron Transport in Bismuth at Liquid Helium Tempratures (open access)

Electron Transport in Bismuth at Liquid Helium Tempratures

To obtain information on the band structure of bismuth, galvanomagnetic potentials were measured in a single crystal at liquid-helium and liquid-nitrogen temperatures. These measurements were analyzed for information on the different carriers, particularly for the existence of a high-mobility band of holes.
Date: May 1964
Creator: Newell, James M.
System: The UNT Digital Library
The Dielectric Constant of Galvinoxyl (open access)

The Dielectric Constant of Galvinoxyl

The molecules in many substances are know to undergo at characteristic temperatures a change in their rotational freedom in the solid state, signifying either a change in structure of the material of the onset of limited rotation of the molecule about some symmetry axis. The purpose of this research was to determine from dielectric constant measurements over the 100°K-420°K temperature range whether or not the organic free radical galvinoxyl and its diamagnetic parent molecule, dihydroxydiphenylmethane, undergo any such transitions.
Date: May 1968
Creator: Mizell, Michael E.
System: The UNT Digital Library
Cross-Section at 15.6 and 16.1 MeV (open access)

Cross-Section at 15.6 and 16.1 MeV

The intent of this investigation is the determination of the values of the Cs-133 (n,2n)Cs-132 cross-section at neutron energies of 15.6 and 16.1 MeV. Neutrons of this energy are produced with comparative ease by means of the D-T reaction, in which deuterons of energy 500 and 750 keV, respectively, are impingent upon a tritium target.
Date: May 1969
Creator: Pepper, George H.
System: The UNT Digital Library
Anisotropic Relaxation Time for Solids with Ellipsoidal Fermi Surfaces (open access)

Anisotropic Relaxation Time for Solids with Ellipsoidal Fermi Surfaces

Many solids have Fermi surfaces which are approximated as ellipsoids. A comprehensive solution for the magnetoconductivity of an ellipsoid is obtained which proves the existence of a relaxation time tensor which can be anisotropic and which is a function of energy only.
Date: May 1971
Creator: Fuchser, Troy Denrich
System: The UNT Digital Library
Cross Section Measurements in Praseodymium-141 as a Function of Neutron Bombarding Energy (open access)

Cross Section Measurements in Praseodymium-141 as a Function of Neutron Bombarding Energy

Using the parallel disk method of activation analysis, the (n,2n) reaction cross section in 141-Pr was measured as a function of neutron energy in the range 15.4 to 18.4 MeV. The bombarding neutrons were produced from the 3-T(d,n)4-He reaction, where the deuterons were accelerated by the 3-MV Van de Graff generator of the North Texas Regional Physics Laboratory in Denton, Texas.
Date: May 1971
Creator: Marsh, Stephen Addison
System: The UNT Digital Library
Phase Shift Determination for Elastic Potential Scattering, Using the IBM 360-50 Computer (open access)

Phase Shift Determination for Elastic Potential Scattering, Using the IBM 360-50 Computer

The primary objective of this paper is to present a computerized method for the extraction of phase shifts from an angular distribution. This was accomplished using a least squares curve fitting routine.
Date: May 1971
Creator: Psencik, James A.
System: The UNT Digital Library
Electrical Conductivity in Thin Films (open access)

Electrical Conductivity in Thin Films

This thesis deals with electrical conductivity in thin films. Classical and quantum size effects in conductivity are discussed including some experimental evidence of quantum size effects. The component conductivity along the applied electric field of a thin film in a transverse magnetic field is developed in a density matrix method.
Date: May 1973
Creator: Meyer, Frederick Otto
System: The UNT Digital Library
Electron Density and Collision Frequency Studies Using a Resonant Microwave Cavity as a Probe (open access)

Electron Density and Collision Frequency Studies Using a Resonant Microwave Cavity as a Probe

Electron densities and collision frequencies were obtained on a number of gases in a dc discharge at low pressures (0.70-2mm of Hg). These measurements were performed by microwave probing of a filament of the dc discharge placed coaxially in a resonant cavity operating in a TM₀₁₀ mode. The equipment and techniques for making the microwave measurements employing the resonant cavity are described. One of the main features of this investigation is the technique of differentiating the resonance signal of the loaded cavity in order to make accurate measurements of the resonant frequency and half-power point frequencies.
Date: May 1973
Creator: Freeman, Ronald Harold
System: The UNT Digital Library
Microwave Properties of Liquids and Solids, Using a Resonant Microwave Cavity as a Probe (open access)

Microwave Properties of Liquids and Solids, Using a Resonant Microwave Cavity as a Probe

The frequency shifts and Q changes of a resonant microwave cavity were utilized as a basis for determining microwave properties of solids and liquids. The method employed consisted of varying the depth of penetration of a cylindrical sample of the material into a cavity operating in the TM0 1 0 Mode. The liquid samples were contained in a thin-walled quartz tube. The perturbation of the cavity was achieved by advancing the sample into the cavity along the symmetry axis by employing a micrometer drive appropriately calibrated for depth of penetration of the sample. A differentiation method was used to obtain the half-power points of the cavity resonance profile at each depth of penetration. The perturbation techniques for resonant cavities were used to reduce the experimental data obtained to physical parameters for the samples. The probing frequency employed was near 9 gHz.
Date: May 1974
Creator: Hong, Ki H.
System: The UNT Digital Library
Effects of Discharge Tube Geometry on Plasma Ion Oscillations (open access)

Effects of Discharge Tube Geometry on Plasma Ion Oscillations

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.
Date: May 1975
Creator: Simmons, David Warren
System: The UNT Digital Library
A Classical Theory of the Dielectric Susceptibility of Anharmonic Crystals (open access)

A Classical Theory of the Dielectric Susceptibility of Anharmonic Crystals

An expression for the dielectric susceptibility tensor of a cubic ionic crystal has been derived using the classical Liouville operator. The effect of cubic anharmonic forces is included as a perturbation on the harmonic crystal solution, and a series expansion for the dielectric susceptibility is developed. The most important terms in the series are identified and summed, yielding an expression for the complex susceptibility with an anharmonic contribution which is linearly dependent on temperature. A numerical example shows that both the real and imaginary parts of the susceptibility are continuous, finite functions of frequency.
Date: May 1976
Creator: Kennedy, Howard V.
System: The UNT Digital Library
Theoretical Cross Section for Light Scattering from Superfluid Helium-4 (open access)

Theoretical Cross Section for Light Scattering from Superfluid Helium-4

The finite lifetime of the bound roton pair is included in the theoretical light scattering cross section to explain the shape of the peak in the observed Raman light scattering cross section in He II. A model Hamiltonian is used to describe interactions between quasiparticles for the helium system. The equation of motion for the bound roton pair state, which is taken to be a collective mode of quasiparticle pairs, is solved. The cross section for light scattering is then derived using Fermi's Golden Rule with the bound roton pair as the final state. Since the bound roton pair can decay into two free phonons, a phenomenological width r is included in the cross section. The peak position and shape of the observed cross section are both fitted using a binding energy of εB = 0.37 K for the bound roton pair.
Date: May 1976
Creator: Latham, W. Peters, Jr., 1948-2016.
System: The UNT Digital Library
Line Width Parameters and Center Frequency Shifts in the Rotational Spectrum of Methyl Cyanide (open access)

Line Width Parameters and Center Frequency Shifts in the Rotational Spectrum of Methyl Cyanide

Measurement of the line width parameters of a molecule is of interest because collision diameters can be calculated from them. This gives an effective size of the molecule when it is involved in interactions with other molecules. Further, specific types of interactions can be inferred from detailed information about the dependence of the line width upon pressure. In this paper, an experiment for measuring line width parameters for methyl cyanide is described and the results of the experiment are analyzed. This investigation was successful in obtaining precise values for the line width parameter for the J-J' = 0-1, J-J'= 1-2, and J-J' = 2-3 transitions of methyl cyanide which agree with experimental values of other researchers where available. It was found that standing waves were the dominant effect in the measurement of center frequency shift.
Date: May 1978
Creator: Swindle, David L.
System: The UNT Digital Library
A Study of L-Shell X-Ray Production Cross Sections Due to [Hydrogen-1], [Helium-4], and [Lithium-7] Ion Bombardment of Selected Thin Rare Earth and ₈₂Pb Targets (open access)

A Study of L-Shell X-Ray Production Cross Sections Due to [Hydrogen-1], [Helium-4], and [Lithium-7] Ion Bombardment of Selected Thin Rare Earth and ₈₂Pb Targets

Thin target L-Shell x-ray production cross sections for protons incident on ₆₂Sm and ₇₀Yb in the energy range of 0.3 to 2.4 MeV/amu, alpha particles incident on ₆₂Sm, ₇₀Yb, and ₈₂Pb in the energy range of 0.15 to 4.8 MeV/amu, and lithium ions incident on ₅₈Ce, ₆₀Nd, ₆₂Sm, ₆₆Dy, ₆₇Ho, ₇₀Yb, and ₈₂Pb in the energy range of 0.8 to 4.4 MeV/amu have been measured. The cross section data have been compared to the planewave Born approximation (PWBA) and the PWBA modified to include binding energy and Coulomb deflection effects. The Lα₁,₂ x-ray production cross sections are best represented by the PWBA modified to include both the binding energy and Coulomb deflection effects (PWBA-BC) over the entire incident ion, incident energy, and target ranges studied. However, the Lγ₁ and Lγ₂,₃,₍₆₎ x-ray production cross sections are best represented by the PWBA except at the lower ion energies, where both the PWBA and PWBA-BC are in disagreement with the data. The comparison of Lα₁,₂/Lγ₂,₃,₍₆₎ ratios to theory reveals that the PWBA-BC does not predict the inflection point substantiated by the data, and the agreement between the data and the PWBA-BC becomes worse as the atomic number of the incident ion increases. Comparison …
Date: May 1978
Creator: Light, Glenn Michael
System: The UNT Digital Library
Microwave Properties of Hyaluronate Solutions Using a Resonant Microwave Cavity as a Probe (open access)

Microwave Properties of Hyaluronate Solutions Using a Resonant Microwave Cavity as a Probe

Physiological functions of a biomacromolecule seem to be closely related to its molecular conformations. The knowledge of any conformational changes due to changes in its environment may lead to a proper understanding of its functions. Hyaluronic acid, a biomacromolecule with unusually high molecular weight and some important biological functions is the subject of the present work. A temperature-dependent transition in hyaluronate solution of 120 mg/ml concentration was observed at physiological temperature. It is shown that this temperature-dependent behavior can be related to the orientational polarizability term in the Debye theory of polar molecules in liquids.
Date: May 1980
Creator: Jani, Shirish K.
System: The UNT Digital Library
A Technique for Increasing the Optical Strength of Single-Crystal NaCl and KCl Through Temperature Cycling (open access)

A Technique for Increasing the Optical Strength of Single-Crystal NaCl and KCl Through Temperature Cycling

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.
Date: May 1983
Creator: Franck, Jerome B. (Jerome Bruce)
System: The UNT Digital Library
Linear and Nonlinear Optical Techniques to Characterize Narrow Gap Semicondutors: (Hg /Cd)Te and InSb (open access)

Linear and Nonlinear Optical Techniques to Characterize Narrow Gap Semicondutors: (Hg /Cd)Te and InSb

Several methods have been developed and used to characterize the narrow gap semiconductors Hg^_xCdxTe (HgCdTe) (0.20<x<0.32) and InSb both in the presence of CO2 laser radiation and in the dark. The results have allowed the determination of certain band parameters including the fundamental energy bandgap Eg which is directly related to x, the mole fraction of Cd. In the dark, characterization of several different samples of HgCdTe and InSb were carried out by analyzing the temperature dependence of the Hall coefficient and the magnetic field positions of the magnetophonon extrema from which their x-values were determined. The quality of the magnetophonon spectra is also shown to be related to the inhomogeneity Ax of the HgCdTe samples. One-photon magneto-absorption (OPMA) spectra have been obtained for x ~ 0.2 samples of p-HgCdTe thin films and n-HgCdTe bulk samples. Analysis of the OPMA transition energies allows the x-value to be determined to within « ±0.001. A method is also discussed which can be used to estimate the sample inhomogeneity Ax. Nonlinear optical properties of semiconductors are not only scientifically interesting to study, but are also proving to be technologically important as various nonlinear optical devices are being developed. One of the most valuable …
Date: May 1986
Creator: McClure, Stephen Warren
System: The UNT Digital Library
Dispersion of the Nonlinear Refractive Index of CS₂ in the Spectral Range of 9-11 μm (open access)

Dispersion of the Nonlinear Refractive Index of CS₂ in the Spectral Range of 9-11 μm

The nonlinear refractive index (n2) of room temperature liquid CS2 in the wavelength range of 9 to 11 micrometers is measured. A line tunable hybrid C02 TEA laser and amplifier system is used for the experiments. In these measurements the well known photoacoustic method is utilized to observe the onset of whole beam self-focusing. The photoacoustic signal in a CS2 cell, much longer than the confocal parameter, is monitored. The departure of the acoustic signal from linear growth marks the critical power for the onset of nonlinearity. It is experimentally verified that the phenomenon is power dependent as expected from self-focusing theory. The value of n2 is then calculated from the theoretical model of self focusing. Measurements of the on-axis irradiance transmitted through the nonlinear material as well as the measurements of beam distortion are used to verify the validity of the photoacoustic method. In all the measurements the on-axis intensity was smaller than the calculated threshold intensity for stimulated Brillouin scattering. The back reflection was monitored to make sure that stimulated Brillouin scattering was not playing a role in the phenomenon.
Date: May 1987
Creator: Mohebi, Mehrdad
System: The UNT Digital Library
Microwave Spectra of ¹³C Isotopic Species of Methyl Cyanide in the Ground, v₈=1 and v₈=2 Vibrational States (open access)

Microwave Spectra of ¹³C Isotopic Species of Methyl Cyanide in the Ground, v₈=1 and v₈=2 Vibrational States

The problem of the quadrupole interaction occurring in a vibrating-rotating C₃v symmetric top molecule has been studied in detail. The quadrupole interaction has been treated as another perturbation term to a general frequency expression accounting for the vibrating-rotating interaction of the molecule so that a complete frequency formula is obtained for both interactions, and from which hyperfine spectral components are predicted and measured. The hyperfine transitions in the ground, and v₈=1 and v₈=2 excited vibrational states of the ¹³C isotopes of methyl cyanide have been investigated in the frequency range 17-72 GHz, primarily in the low J transitions (0≤J≤3). The study of the ground state of isotope i3CH3i3CN, and the v₈=1, v₈=2 excited vibrational states for all the isotopes have been conducted here for the first time. A substantial perturbation has been discovered and discussed at the ΔJ=3→4 transitions within the Kl=1 sets in the v₈=1 mode for isotopes ¹³CH₃CN and CH₃¹³CN. A total of 716 hyperfine transitions have been assigned from measurements, only 7 of which have been measured previously. A total of 84 molecular constants have been reported; 70 of these constants are derived for the first time from microwave data.
Date: May 1988
Creator: Tam, Hungsze
System: The UNT Digital Library
Optical Nonlinearities in Semiconductors for Limiting (open access)

Optical Nonlinearities in Semiconductors for Limiting

I have conducted detailed experimental and theoretical studies of the nonlinear optical properties of semiconductor materials useful for optical limiting. I have constructed optical limiters utilizing two-photon absorption along with photogenerated carrier defocusing as well as the bound electronic nonlinearity using the semiconducting material ZnSe. I have optimized the focusing geometry to achieve a large dynamic range while maintaining a low limiting energy for the device. The ZnSe monolithic optical limiter has achieved a limiting energy as low as 13 nJ (corresponding to 300W peak power) and a dynamic range as large as 105 at 532 nm using psec pulses. Theoretical analysis showed that the ZnSe device has a broad-band response covering the wavelength range from 550 nm to 800 nm. Moreover, I found that existing theoretical models (e.g. the Auston model and the band-resonant model using Boltzmann statistics) adequately describe the photo-generated carriers refractive nonlinearity in ZnSe. Material nonlinear optical parameters, such as the two-photon absorption coefficient β_2=5.5cm/GW, the refraction per unit carrier density σ_n=-0.8∗10^-21cm^3 and the bound electronic refraction n_2=-4∗10^-11esu, have been measured via time-integrated beam distortion experiments in the near field. A numerical code has been written to simulate the beam distortion in order to extract the …
Date: May 1990
Creator: Wu, Yuan-Yen
System: The UNT Digital Library
L-Shell X-Ray Production Cross Sections for ₂₀Ca, ₂₆Fe, ₂₈Ni, ₂₉Cu, ₃₀Zn, ₃₁Ga, and ₃₂Ge by Hydrogen, Helium, and Lithium Ions (open access)

L-Shell X-Ray Production Cross Sections for ₂₀Ca, ₂₆Fe, ₂₈Ni, ₂₉Cu, ₃₀Zn, ₃₁Ga, and ₃₂Ge by Hydrogen, Helium, and Lithium Ions

L-shell x-ray production cross sections are presented for Fe, Ni, Cu, Zn, Ga, and Ge by 0.5- to 5.0-MeV protons and by 0.5- to 8.0-MeV helium ions and Ca, Fe, Ni, Cu, and Ge by 0.75- to 4.5-MeV lithium ions. These measurements are compared to the first Born theory and the perturbed-stationary- state theory with energy-loss, Coulomb deflection, and relativistic corrections (ECPSSR). The results are also compared to previous experimental investigations. The high precision x-ray measurements were performed with a windowless Si(Li) detector. The efficiency of the detector was determined by the use of thin target atomic-field bremsstrahlung produced by 66.5 keV electrons. The measured bremsstrahlung spectra were compared to theoretical bremsstrahlung distributions in order to obtain an efficiency versus energy curve. The targets for the measurement were manufactured by the vacuum evaporation of the target element onto thin foils of carbon. Impurities in the carbon caused interferences inthe L-shell x-ray peaks. Special cleansing procedures were developed that reduced the impurity concentrations in the carbon foil, making the use of less than 5 μg/cm^2 targets possible. The first Born theory is seen to greatly overpredict the data at low ion energies. The ECPSSR theory matches the data very well at …
Date: May 1992
Creator: McNeir, Michael Ridge
System: The UNT Digital Library