Physical Sciences and Mathematics Commons^™

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.

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) …

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

Masters Theses

No abstract provided.

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

Masters Theses

No abstract provided.

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 …

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 …

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.

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; …

Linear Pulsation Analysis Of Cluster Cepheid Variables, Charles E. Needham

Physics & Astronomy ETDs

Models for thirteen classical Cepheids found in galactic clusters or associations are analyzed. The models are calculated using the most recently published photometric data and theoretical evolutionary tracks. The linearized equations of mass, momentum and energy conservation are solved subject to an infinitesimal radial perturbation of each equilibrium model. The equations are first solved in the adiabatic approximation. This solution is then used as the initial value for the iterative solution of the non-adiabatic equations. The linearized analysis provides information on pulsation periods of fundamental and harmonic modes, stability against pulsations and phase differences between various physical parameters, such as …

Ion‐Pair Theory Of Concentrated Electrolytes. Iii. Variational Principle, Frank Stillinger, Ronald White

Center for Advanced Mineral and Metallurgical Processing (CAMP)

Two major contributions are devised for that theory of concentrated electrolytes which by convention regards the ions as completely paired into uncharged dipolar “molecules.” First, a more satisfactory expression is obtained for the wavelength‐dependent static dielectric “constant” ε(k). Second, a variational principle for Helmholtz free energy F is displayed whose minimization with respect to the ion‐pair size distribution p(1) serves to determine both F and p(1). In anticipation of future numerical applications, a binary collision approximation is specified for the short‐range interaction aspect of the functional F[p(1)].

Ion‐Pair Theory Of Concentrated Electrolytes. Iv. Ion Atmosphere Charge Distribution, Frank Stillinger, Ronald White

Center for Advanced Mineral and Metallurgical Processing (CAMP)

Arguments are presented indicating that the large‐size limiting behavior of the ion‐pair size distribution is qualitatively the same both with, and without, Coulomb interactions between ions. This in turn implies that the static dielectric response function ε0 / ε(k) derived in the preceding paper is nonanalytic at k = 0. The specific singular behavior of this response requires a branch cut along the imaginary k axis. It furthermore induces an r−8 tail in the ion atmosphere charge distribution at finite electrolyte concentration.

Construction Of A Small Vacuum Ultraviolet Spectrograph, Dale A. Eding

Masters Theses

No abstract provided.

Length And Velocity Formulas In Approximate Oscillator-Strength Calculations, Anthony F. Starace

Anthony F. Starace Publications

The matrix element for electric dipole transitions is correctly given by the length formula in the Hartree-Fock, configuration-interaction, and related approximations, which involve the diagonalization of an approximate, but nonlocal, Hamiltonian.

Hydrostatic Pressure Effects On The Epr Spectrum Of V2+:Al203, Jonathan Lloyd Albain

Masters Theses

No abstract provided.

Lorentz-Invariant And Lorentz-Noninvariant Approximation Techniques In The Spin-Parity Analysis Of Four-Pion Resonances, Wilson C. Lu

Masters Theses

No abstract provided.

Spectroscopic Measurement Of The Electron Temperature In The Tenuous Argon Ion Laser Plasma, Dane Danijel Bicanic

Physics Theses & Dissertations

The validity of the line intensity ratio technique for measuring the electron temperature was examined for an argon plasma with a "population inversion" i.e., the number of ions with electrons in the upper 4p levels was greater than in the lower 4s levels. The line intensities from these levels, the argon ion lasing transitions, were measured in a pulsed tenuous plasma at 110μ Hg produced by discharging a capacitor through a tube 2m long and 7mm inside diameter. The electron impact cross sections for simultaneous excitation and ionization as measured by Latimer and St. John were used and averaged over …

Mössbauer Spectroscopy Study Of The Spin‐Flop Transition In Fe‐Doped Mnf2, C. R. Abeledo, Richard B. Frankel, A. Misetich, N. A. Blum

Physics

Measurements of the hyperfine interaction in Fe^{+ +} in MnF₂ in external fields above the spin‐flop field at 4.2 K are reported and a value of g⊥ = 2.13 is derived, in good agreement with theory.

Track Theory And Radiation Quality, Robert Katz

Robert Katz Publications

Radiation detection and damage data from several physical, chemical, and biological systems have been analyzed by a unified track theory, in which observed effects are attributed to the interaction of secondary electrons with the medium. Gamma-ray dose-response curves are combined with calculations of the spatial dose distribution about an ion's path to yield dose-response curves (survival curves) for heavy ion bombardment, through appropriately defined parameters. Perplexing phenomena associated with high LET radiation are sorted out according to track regime (grain-count or track-width), inactivation mode (gamma-kill or ion-kill), structural complexity (elementary, cellular, multicellular), and end-point. The central problem in assigning a …