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The Shubnikov-de Haas Effect in N-Type Indium Antimonide (open access)

The Shubnikov-de Haas Effect in N-Type Indium Antimonide

The Shubnikov-de Haas effect is an oscillation in the electrical resistivity or conductivity of a metal, semimetal, or semiconductor as a function of changing magnetic field which occurs at low temperatures. The effect is caused by the quantization of the momentum and energy of the charge carriers by the magnetic field. Since the nature of the oscillation depends strongly on the energy band structure of the material in which it is measured, the effect could be quite useful as an investigative tool. Its usefulness has been limited, however, by the uncertainty as to the functional form of the relationship between the measured oscillations and the parameters characterizing the material. One purpose of the present study is to extend the usefulness of the Shubnikov-de Haas effect by experimentally determining the functional form appropriate for a material such as n-type indium antimonide. The second purpose of the study is to determine values for the parameters which characterize the band structure of indium antimonide. The curve fitting procedure is found to be a powerful tool for investigating band structure. All computer programs used in processing the data, fitting the data, and comparing the results with the Kane model are given.
Date: August 1975
Creator: Stephens, Anthony Earl
System: The UNT Digital Library
Collision Broadening of Microwave Spectral Lines of Monomeric Formaldehyde and Formic Acid (open access)

Collision Broadening of Microwave Spectral Lines of Monomeric Formaldehyde and Formic Acid

Line width parameters for a number of spectral lines in the pure rotational spectrum of formaldehyde (CH20) and formic acid (HCOOH) have been measured using a sourcemodulated microwave spectrograph. All transitions studied in this investigation were of the type ΔJ=O (i.e. Q-branch transitions), with ΔK-1=0 and ΔK+1 =+l. The center frequencies of the measured lines varied from 8662.0 MHz to 48612.70 MHz. The experimentally determined collision diameters for self broadening interactions involving HCOOH and CH2 Q molecules were found to be 2 - 27 per cent less than those calculated by the Murphy-Boggs theory of collision broadening. Much better agreement between a simplified broadening scheme for symmetric top molecules and the observed foreign-gas collision diameters is obtained by using Birnbaum's theory.
Date: August 1975
Creator: Venkatachar, Arun C.
System: The UNT Digital Library
Investigation of the Effects of Compressive Uniaxial Stress on the Hole Carriers in P-type InSb (open access)

Investigation of the Effects of Compressive Uniaxial Stress on the Hole Carriers in P-type InSb

The influence of uniaxial compression upon the Hall effect ad resistivity of cadmium-doped samples of InSb at 77 K, 64 K, and 12 K are reported. Unilaxial compressions as high as 6 kbar were applied to samples oriented in the {001} and {110} directions. The net hole concentration of the samples were about 5x10^13 cm^-3 at 77 K as determined from the Hall coefficient at 24 kilogauss. The net concentration of hole carriers decreases and then increases exponentially with stress at 77 k and 64 k, while at 12 k there is only a monotonic increase of carrier concentration with stress. Analysis of the hole concentration as a function of stress shows the presence of a deep acceptor level located about 90 meV above the valence band edge in additionb to the 10 meV vadmium acceptor level. The shallow acceptor level does not split with stress. The hole density data is represented very well by models which describe both the variation in the net density of states and motion of the acceptor levels as a function of stress.
Date: December 1975
Creator: Vaughn, Bobby J.
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
Calculations of Nuclear Energies Using the Energy Density Formalism (open access)

Calculations of Nuclear Energies Using the Energy Density Formalism

The energy density formalism (EDF) is used to investigate two problems. The EDF is a phenomenological method that incorporates as much knowledge of infinite nuclear matter as possible. In this formalism the energy of the nucleus is expressed as a functional of its density. The nucleus energy is obtained by minimizing the function, with respect to the density. In this report, the EDF is used to investigate the mercury isotope shift anomaly following the aforementioned suggestion. Specifically, nucleon densities with different degrees of central depression are generated. Energies corresponding to these densities are obtained. The density with the minimum energy is the preferred one. Based on the findings of the present work, it can be concluded that a central depression in the lighter mercury isotopes does not-appear- to be a possible explanation for the isotope shift anomaly. And the anomaly remains unresolved.
Date: August 1975
Creator: Pu, William Wei-Ta
System: The UNT Digital Library
L X-Ray Production in the Rare Earths by 0.33-2.66-MeV/amu Carbon- and 0.50-2.25-MeV/amu Oxygen-Ion Bombardment (open access)

L X-Ray Production in the Rare Earths by 0.33-2.66-MeV/amu Carbon- and 0.50-2.25-MeV/amu Oxygen-Ion Bombardment

Experimentally measured L-shell x-ray production cross sections are presented for 8-36-MeV oxygen-ion bombardment of Ce, Pr, Sm, Eu, Dy, and Ho; for 4-32-MeV carbon-ion bombardment of La and Yb; for 6-32-MeV carbon-ion bombardment of Pr, Nd, Sm, and Dy; and for ll-29-MeV carbon-ion bombardment of Ce, Eu, Gd, and Ho. Theoretical predictions via the plane wave Born approximation (PWBA) with corrections for increased binding of target electrons and Coulomb deflection of the incident projectile tend to underestimate the experimental data; and this underestimation tends to get worse at the low- and high-energy ends of the range of energies used in this work.
Date: August 1975
Creator: Pepper, George H.
System: The UNT Digital Library