Physical Sciences and Mathematics Commons^™

Shubnikov-De Haas Effect And Magnetic Breakdown In Be , David J. Sellmyer, I.S. Goldstein, B.L. Averbach

David Sellmyer Publications

Magnetic breakdown in the basal plane of Be was investigated in fields up to 150 kG. Geometrical aspects of the open orbits caused by breakdown are discussed. An estimate of 30 kG for the characteristic breakdown field is obtained by applying the theory of Falicov et al. Shubnikov-de Haas frequency measurements are reported for the central-cigar cross section. These measurements are relevant to a recent conjecture that the Onsager-Lifshitz quantization scheme may be violated in the presence of magnetic breakdown.

Average Solid Angle For Detection Of Photon Pair Positron Annihilations, Albert S. Ferrari

Masters Theses

No abstract provided.

A Study Of Isospin Mixing In 16O Near 18 Mev Exitation Energy, Li-Yun Kuo

Masters Theses

No abstract provided.

Even-Parity Lattice Resonances And Anharmonicity In Ki: Ag+, Roger D. Kirby

Roger Kirby Publications

We report here the observation of four impurity-induced lattice resonances in KI:Ag+. In addition to the well-known T1u symmetry resonant mode at 17.3 cm-1, we have observed two even-parity resonant modes of A1g and Eg symmetries at 25 and 16.35 cm-1, respectively, and a T1u symmetry gap mode at 86.2 cm-1. The two even-parity modes were detected using far-infrared spectroscopic techniques with the sample in an external electric field. The field induces a strong mixing of the modes of opposite parity and results in large field-induced shifts. The Eg symmetry resonance has also been seen in the Raman spectrum of …

Thermionic Space Charge Oscillations, William Carl

Masters Theses & Specialist Projects

Thermionic electrons emitted into a potential well will produce radiation, the frequency of which is determined by the transit time of the electrons. This paper investigates the case where radiation is produced by a vacuum tube in which two Pierce guns face each other, one acting as the emitter, the other acting as a reflector. Symmetry and the focusing of the electron beam by the Pierce guns make it possible to make an accurate determination of the electron transit time. Measurements showed that the period of the oscillation was 1.5 times the period required for an electron to traverse the …

Mössbauer-Effect Studies Of The Phase Transitions In Antiferroelectric Pbzro₃ And Ferroelectric Pbti₀.₀₂Zr₀.₈O₃, James P. Canner, C. M. Yagnik, Robert Gerson, William Joseph James

Physics Faculty Research & Creative Works

The Mössbauer spectra were studied for the antiferroelectric compound PbZrO₃ and for the closely related ferroelectric PbTi_0.2Zr_0.8O₃. In both cases, a substitution of 5-mol% BiFeO₃ was made to permit the Mössbauer measurements. Little difference was found in the isomer shift in these compounds, whether they were in the ferroelectric, antiferroelectric, or cubic state, indicating that the bonding character is not affected by the transitions among the states. There was a pronounced and approximately equivalent dip in the recoil-free fraction at the Curie points of both the antiferroelectric and ferroelectric materials, associated with …

Cellular Inactivation By Heavy Ions, Neutrons, And Pions, Robert Katz, S. C. Sharma, M. Hamayoonfar

Robert Katz Publications

The delta-ray theory of the inactivation of cells by energetic heavy ions describes cellular survival after heavy ion bombardment through a two-component survival model, in which 4 operational parameters (E₀,m₀, σ₀, and κ) describe the response of a particular cellular variety in a particular ambient condition, for an arbitrary radiation environment. The quantities m and E₀ are the extrapolation number and extrapolated D-37 dose of the survival curve after gamma-ray irradiation. The quantities σ₀ and κ are found from the initial slope of survival curves after irradiation with ions of different LET, …

Measurement Of Currents In Lake Mead With The Deep Water Isotopic Current Analyzer (Dwica), J. J. Sartoris, D. A. Hoffman, Bureau Of Reclamation

Publications (WR)

In Nov 1967, a Deep Water Isotopic Current Analyzer (DWICA) was used to study current patterns in the Boulder Basin of Lake Mead to determine if low-quality water from Las Vegas Bay might enter the Southern Nevada Water Project intake on Saddle Island. Secondary objectives were to study the general current patterns in Boulder Basin and the effect of power discharges at Hoover Dam on these currents. Results of current measurements at 3 stations in Boulder Basin are given. Observations indicate a definite possibility that low-quality water from Las Vegas Bay might enter the water intake on Saddle Island. Current …

Nuclear-Magnetic-Resonance Studies Of The Semiconductor-To-Metal Transition In Chlorine-Doped Cadmium Sulfide, Frank D. Adams, David C. Look, Carlton L. Brown, Donald R. Locker

Physics Faculty Publications

Spin-lattice relaxation times (T₁) and Knight shifts were measured for Cd¹¹³ nuclei in 12 CdS crystals doped with various amounts of chlorine. Hall coefficients were measured in order to estimate conduction-electron concentrations. Data were obtained for all samples at 300 °K and for some highly doped samples at 77, 4.2, and 2.13 °K. Metallic properties were observed in all samples having electron concentrations n>2×10¹⁸ cm^-3. At 300 °K, we find 1/T₁∝n for nonmetallic samples and 1/T₁∝n^2/3 when samples are metallic. The latter proportionality continues to hold at lower …

Comment On Electron Scattering In The Image Potential Well, Pavel Smejtek, M. Silver

Physics Faculty Publications and Presentations

Comments are made on the model of electron injection into SiO₂ proposed by Berglund and Powell. Their assumptions on electron scattering, disregarding the change of the escape cone with the distance from the emitter, lead to serious underestimation of the injected current. Two alternative models of electron injection, based solely on elastic scattering are discussed and do not predict the experimental results. We suggest that observed field dependence of the injected current into SiO₂ indicates that energy relaxation associated with the injected electrons is responsible for the voltage dependence of the current.

Studies Of The Potential Curve Crossing Problem I. Analysis Of Stueckelberg's Method, W. R. Thorson, John B. Delos, Seth A. Boorstein

Arts & Sciences Articles

A detailed critical analysis is made of Stueckelberg's treatment of inelastic transitions at a crossing of two potential curves. Using an asymptotic method analogous to the WKB approximation, Stueckelberg obtained the well-known Landau-Zener-Stueckelberg (LZS) formula for the inelastic transition probability. His method involved the determination of "connection formulas" linking amplitudes associated with his asymptotic approximants on either side of the crossing-point region. Here we show that (a) Stueckelberg's asymptotic approximants are just the WKB approximants for elastic scattering on the adiabatic (noncrossing) potential curves; (b) Stueckelberg's method for obtaining the connection formulas can be put on a rigorous footing, including …

Evidence For The Existence Of Two Stable Sites For Cobalt Impurity Atoms In Aluminum, Arun Venkatachar

Dissertations and Theses

Using Fe⁵⁷Mössbauer spectroscopy, two alternative sites occupied by cobalt (10^-4 at. % ) impurity atoms in aluminum have been isolated. The substitutional site A is the stable position after annealing the sample above 840 K, followed by a rapid quench. The impurity atoms in site A are characterized by a single line Mössbauer spectrum (indicative of a cubic environment), a room-temperature f = 0.502 (r. m. s. displ. 0.071 A) and an I. S. (reI. to Fe) = -0.421 mm/sec. For anneals below 770 K the cobalt atoms migrate to site B, which is characterized by a …

Application Of The Method Of Lattice Statics To Vacancies In Aluminum, Larry Boyer, John R. Hardy

John R. Hardy Papers

In this paper the method of lattice statics is applied to the calculation of the atomic displacements about a vacancy in aluminum using a fifth-neighbor force-constant model for the dynamical matrix and the vacancy-host lattice interaction. The strain-field interaction energy between two vacancies is similarly calculated. The main object of this work is to demonstrate the important modifications of earlier results, obtained for a first- and second-neighbor force-constant model, when one uses the fifth-neighbor model designed to give a significantly better fit to the measured phonon dispersion curves. In particular it is demonstrated that the displacements about the vacancy continue …

13th Annual Rocky Mountain Spectroscopy Conference

Rocky Mountain Conference on Magnetic Resonance

Program and abstracts from the 13th annual meeting of the Rocky Mountain Spectroscopy Conference, hosted by the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Denver, Colorado, August 9-10, 1971.

Elastic Scattering Of Alpha Particles From 12C, Hsi-Chiu Liu

Masters Theses

No abstract provided.

Energy Calibration Of The Western Michigan University Model En Tandem Accelerator, Michael Joseph Parrott

Masters Theses

No abstract provided.

On The Molecular Theory Of Dielectric Polarization In Rigid‐Dipole Fluids, John D. Ramshaw

Physics Faculty Publications and Presentations

A molecular theory is developed for the polarization P(r) produced by a weak position‐dependent external electric field E₀(r) in a finite fluid system, of arbitrary shape, composed of rigid polar molecules. The theory differs from earlier work in that no assumption is made concerning the form of the electrostatic constitutive relation. [The usual assumption in this regard is that P(r) = (ε–1) E(r) / 4π, where E(r) is the total Maxwell electric field. The “dielectric constant” ε is well defined only if the relation between P(r) and E(r) …

An Application Of Spectroscopic Techniques To The Measurement Of Electron Density And Temperature In A Brush Cathode Plasma, Ramabhai M. Patel

Physics Theses & Dissertations

A brief review of the Langmuir probe, microwave and spectroscopic techniques most commonly used to make measurements .of plasma electron temperature and density is presented. Of these various methods, certain spectroscopic methods are applied to the measurements of electron density and temperature in a helium brush cathode plasma. The density measurement is based on the manner in which a series of Stark broadened spectral lines merges into an apparent continuum before the normal series limit is reached. This approach met with only limited success in that the density could be determined only by extrapolating the data obtained. Primarily because of …

Crystal Structure Determination Of Β-Lactoglobulin From Electron Micrographs, Richard Roeter

Dissertations and Theses

Often electron micrographs exhibit a repeating structure. Sometimes this repeating structure satisfies the definition of a crystal in that it has a three dimensional repeating structure. If the unit cell structure of this repeating structure can be determined it can be used to help categorize different sections of a particular sample. In some cases, the use of optical diffraction analysis of electron micrographs with repeating structure is a method of determining the unit cell structure.

Samples of β-Lactoglobulin were prepared for viewing in the electron microscope using both the crystalline material and carbon replicas of the crystal surface. Because the …

Measurement Of The Average Solar Neutron Flux And Its Correlation With Solar Activity, Pyung Syk Ro

Physics & Astronomy ETDs

Data from the University of New Mexico High Energy Neutron Detector flown on NASA satellite OSO-VI arc analyzed with the aim of detecting neutrons from the sun. The detector is a proton recoil telescope capable of directional discrimination and responsive to neutrons of energies between 20 and 200 MeV with an effective average efficiency for this analysis of 10^-4 and an effective area of 80cm². The detector was located in a wheel compartment of OSO-VI and scanned the sun once per revolution of the wheel at a rate of 30 rpm. The satellite was launched on August …

Laser Induced Optical Modulation In Zinc Selenide, Donald Edward Everett

Master's Theses

The experiments reported here with zinc selenide have a two-fold purpose. First, by using basically the same experimental set-up as Conway did, we are attempting to duplicate this LIMA using zinc selenide instead of cadium sulfide. Unlike his set-up, primarily one laser chopping frequency was used. Also, only one laser wavelength, 632.8 nanometers, was available, where Conway used lasers of wave­ lengths 647.1 nanometers and 530.8 nanometers. Another main difference is that in earlier works by Conway, laser pulse duration was of the order of 40 milliseconds, whereas the present duration is approximately 2.5 milliseconds. It was observed that the …

High-Pressure Equation Of State For Nacl, Kcl, And Cscl, Daniel L. Decker

Faculty Publications

A calculation of the equation of state for NaCl from a Mie-Grüneisen equation was repeated using more accurate values of the zero-pressure compressibility. It was also extended to KCl and CsCl. An analysis of this approach to pressure calibration indicates that it will yield pressures with about the same accuracy as can be presently achieved by experimental measurements above 25 kbar, and thus furnishes a temporary practical pressure scale.

Increasing The Efficiency Of A Surface Ionization Mass Spectrometer, Thomas Curtis Adams

Physics & Astronomy ETDs

An Avco surface ionization mass spectrometer (model 90,000) was installed at the Los Alamos Scientific Laboratory in February, 1968. Since that date this machine has been used as a production instrument for the isotopic analysis of uranium and plutonium samples. During 1969, it was realized that a problem inherent in the ionization mechanism of the instrument was degrading the accuracy of results, and that the number of man-hours expended in reducing data had become excessive. As soon as this situation became apparent, corrective action was initiated to reduce the effect of the ionization problem and to decrease the amount of …

Raising Of Discrete Levels Into The Far Continuum, J.L. Dehmer, Anthony F. Starace, U. Fano, J. Sugar, J.W. Cooper

Anthony F. Starace Publications

Broad peaks observed in the photoabsorption spectra of rare earths ∼10-20 eV above the 4d edge are attributed to transitions 4d¹⁰4f^N→4d⁹4f^N+1. Exchange interaction splits the 4d⁹4f^N+1 configuration and raises some multiplets by ∼20 eV. Autoionization to 4d⁹-4f^Nεf broadens the high levels. The interpretation extends to p→d processes observed in the absorption of synchrotron light by transition elements.

Radiation Induced Color Centers In Potassium Silicate Glasses Containing Lead, Ibrahim Abou-Seif Henry

Archived Theses and Dissertations

No abstract provided.

Some A. C. Properties Of Lead-Borate Glasses, Salah El-Din El-Nahwy

Archived Theses and Dissertations

No abstract provided.

Radiation Induced Color Centers In Alkali Silicate Glasses, Ramez Morgan Louca

Archived Theses and Dissertations

No abstract provided.

Intensity Ratios For Polarized Refracted Light Near The Critical Angle., Stephanie Layne Moore

Physics & Astronomy ETDs

It was undertaken to investigate the intensity ratio of refracted light polarized parallel and perpendicular to the plane of incidence. The primary object of the experiment was to obtain this ratio for light incident at very nearly the critical angle on a water-air interface, the light having first passed through the water. A laser was used to produce the light beam and the experimental results were compared with the theory propounded by Fresnel for infinite plane waves and elsewhere asserted to hold for bound plane waves. As this theory predicted a ratio of the square of the refractive index (n) …

On The Interaction Of Aluminium And Iron Calcium Borate Glasses And Its Effect On The Properties Of Their Composites, Sherif K. Arif

Archived Theses and Dissertations

No abstract provided.

Calculation Of Point-Defect Energies And Displacements In Alkali Halides Using The Lattice-Statics Method, Arnold Karo, John Hardy

John R. Hardy Papers

The method of lattice statics, in the zero-order approximation, is used to evaluate the Schottky-pair formation energies and the displacement fields about positive- and negative-ion vacancies for all alkali halide crystals with rock-salt structures. The deformation-dipole model, used extensively in earlier work on the lattice dynamics of these crystals, is employed to describe the host lattice. Long-range Coulomb interactions are included explicitly, and short-range repulsive interactions are described by a simple Born-Mayer potential. Comparison is made with earlier Mott-Littleton-type calculations and very satisfactory agreement is found. Comparison with available experimental values is somewhat less satisfactory, particularly regarding the lithium salts; …