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Cw Laser Oscillations And Tuning Characteristics Of Neodymium-Doped Lithium Niobate Crystals, Laird D. Schearer, Michèle Leduc, J. Zachorowski

Physics Faculty Research & Creative Works

We have obtained over 250 mW of CW laser emission at 1084 nm from a neodymium-doped single crystal of lithium niobate when the rod was end pumped by 1 W from a Kr⁺ laser at 752 nm, Thresholds of less than 30 mW are obtained with a weak output coupler, rising to 220 mW with a 25 percent transmitting output mirror. The laser could be tuned over 3 nm around the peak at 1084.4 nm with a thirl, uncoated etalon in the cavity. Copyright © 1987 by The Institute of Electrical and Electronics Engineers, Inc.

Evaluation Of The Reduction Of The Nonadiabatic Hyperspherical Radial Equation To The First Order, Steven L. Carbon

Retrospective Theses and Dissertations

In this paper we examine the effectiveness of reducing the second order radial equation, of the hyperspherical coordinate solution to the two-electron Schrodinger equation, into a set of coupled first order linear equations as suggested by Klar. All results have been obtained in a completely nonadiabatic formalism thereby ensuring accuracy. We arrive at the conclusion that our application of the reduction process is in some way inconsistent and suggest a possible resolution to this anomaly.

Electronic Structure, Photoemission, And Magnetism In Gd2Co And Er2Co Glasses, Sitaram Jaswal, David J. Sellmyer, M. Engelhardt, Z. Zhao, A.J. Arko, K. Xie

David Sellmyer Publications

The electronic and magnetic structures of amorphous Gd₂Co and Er₂Co are studied by ultraviolet and x-ray photoemission measurements and band calculations. The spectra for both glasses show a band of Co 3d levels centered at a binding energy E_B of about -1.0 eV and peaks arising from 4f levels at E_B=-8.4 eV and E_Bapeq2-5–9 eV for Gd and Er, respectively. Magnetization data have shown that a-Gd₂Co possesses a ferrimagnetic structure with a small Co moment. The linear-muffin-tin-orbital method is used to perform self-consistent, spin-polarized calculations in …

Temporary Anion States Of Polyatomic Hydrocarbons, Kenneth D. Jordan, Paul Burrow

Paul Burrow Publications

Contents

I. Introduction

II. Electron Transmission Spectroscopy

A. Background

B. Interpretation of Transmission Data

III. Alkenes, Dienes, and Polyenes

A. Ethylene and Alkyl-Substituted Ethylenes

B. Butadiene, Hexatriene, and Octatetraene

C. Other Conjugated Dienes

D. Cyclooctatetraene

E. Nonconjugated Dienes

IV. Alkynes

A. Acetylene and Alkyl-Substituted Acetylenes

B. Cyclic Acetylenes

C. Butadiyne and 2,4-Hexadiyne

V. Aromatic Systems

A. Benzene and Alkyl-Substituted Benzenes

B. Naphthalene, Anthracene, and Tetracene

C. Styrene and cis- and trans-Stilbene

D. Biphenyls

E. Triptycene, Dibenzonorbornadiene, and Related Compounds

VI. Halogen-Containing Compounds

A. Saturated Compounds

B. Unsaturated Compounds

VII. Conclusions

VIII. Acknowledgment

IX. References

X. Bibliography of Studies …

Differential Cross Sections For Ionization Of Water Vapor By High-Velocity Bare Ions And Electrons, J. H. Miller, W. E. Wilson, S. T. Manson, M. Eugene Rudd

M. Eugene Rudd Publications

A semiempirical model of single differential cross sections (SDCS) for ionization of water vapor by fast electrons and bare ions is presented. At low secondary-electron energy, the model is based on an asymptotic expansion of the first Born approximation with coefficients, that are independent of projectile properties, evaluated from experimental photoabsorption and protonimpact ionization data. As the secondary-electron energy increases, the model converges to a binary-encounter approximation. Comparisons with measured differential, total, and dissociative cross sections for ionization of water by fast electrons are used to test the model. For primary electrons with energy greater than about 500 eV, agreement …

Mössbauer Spectroscopy Of Reduced Ferritin, Richard B. Frankel, G. C. Papaefthymiou, G. D. Watt

Physics

No abstract provided.

Hydrodynamic Fluctuations In A Fluid Under Constant Shear, Alejandro Garcia, M. Malek Mansour, G. Lie, E. Clementi, M. Mareschal

Faculty Publications

No abstract provided.

Fluctuating Hydrodynamics In A Dilute Gas, Alejandro Garcia, G. Lie, E. Clementi

Faculty Publications

Hydrodynamic fluctuations in a dilute gas subjected to a constant heat flux are studied by both a computer simulation and the Landau-Lifshitz formalism. The latter explicitly incorporates the boundary conditions of the finite system, thus permitting quantitative comparison with the former. Good agreement is demonstrated.

A Mössbauer Effect Study Of The Structural And Magnetic Properties Of Y₂(Fe₁₋ₓalₓ)₁₄B, Ying-Chang Yang, Dwayne E. Tharp, Gary J. Long, Oran Allan Pringle, William Joseph James

Chemistry Faculty Research & Creative Works

The crystallographic and magnetic properties of Y₂(Fe₁₋ₓAlₓ)₁₄B, where x equals 0.00, 0.02, 0.04, 0.06, and 0.08, have been investigated by Mössbauer spectroscopy and magnetic measurements at room temperature and 85 K. Magnetic anisotropy and magnetization changes with aluminum substitution indicate that, because of size, the aluminum preferentially occupies the j₂ site over the remaining five crystallographically nonequivalent iron sites. This preferential occupation has been confirmed by Mössbauer spectral studies, which indicate that the compositional variation of the hyperfine field for each site is related to the number of near-neighbor aluminum atoms for the site. This compositional variation is helpful in …

Anneal Induced Changes In Amorphous Semiconductor Multilayers, David D. Allred, Jesus González-Hernández, O. V. Nguyen

Faculty Publications

We have prepared, heat treated and characterized various amorphous semiconductor periodic multilayers and ultrathin films. These were prepared by several vapor deposition techniques at substrate temperatures ranging from 25°C to 300°C and possessed periodicities from 22 to 400Å. Films were subjected to isochronal thermal treatments at progressively higher temperatures. Two effects were observed: enhanced diffusion and retarded crystallization. Interdiffusion, at rates which are many orders of magnitude higher than those anticipated from crystalline data, was observed in a-Si/a-Ge multilayers. Crystallization of germanium, the more readily crystallized member of the couple, is retarded; the extent depends on the thickness of the …

Contribution Of Transfer Ionization To Total Electron Capture From A Helium Target, J. A. Tanis, M. W. Clark, R. Price, Ronald E. Olson

Physics Faculty Research & Creative Works

The contribution of transfer ionization (TI) to total electron capture has been measured for O^q+ ions (q=5, 6, 7, and 8) colliding with helium at energies from 0.5 to 1.5 MeV/u. These measurements, along with other published results, suggest a maximum TI contribution to total capture of 0.15q0.5 at E (in keV /u)q0.5100 The results demonstrate that the failure to account for transfer ionization in total single-charge-transfer cross sections may lead to large discrepancies between experiment and theory. © 1987 The American Physical Society.

Oxidation Kinetics Of Polycrystalline Lacro3, Chikung J. Yu, Don M. Sparlin, Harlan U. Anderson

Physics Faculty Research & Creative Works

The oxidation kinetics of polycrystalline LaCrO3 were determined by measuring the time and temperature dependence of the weight and conductivity change of reduced samples. A region of fast diffusion followed by a smaller, slower diffusion "tail" was observed in the thermogravimetric measurements. This observation can be interpreted as the rapid diffusion along the grain boundaries and subsequent diffusion into the body of the grain. The absence of the "tail" in the conductivity measurements is due to the high hole mobility along the boundaries. Copyright © 1987, Wiley Blackwell. All rights reserved.

Ionization And Charge Exchange In Multiply-Charged-Ion-Helium Collisions At Intermediate Energies, M. L. Mckenzie, Ronald E. Olson

Physics Faculty Research & Creative Works

A Bohr classical model for He is applied to multiply charged ions colliding with He at intermediate energies. Reactions studied are single-electron capture, single and double ionization, and electron-capture ionization for projectile charge states q=1+ to 100+, and the energy range E=1-5 MeV/amu. The dominant electron-removal collision process is single ionization. For the higher-charge-state ions, single-charge exchange is found to be primarily due to transfer ionization, a two-electron process where one electron is ionized and the other is captured by the projectile. For low-charge states, the single- and double-ionization cross sections are close to the expected q² and q …

Positronium Formation From Li And Na Atoms By Use Of Pseudopotential, Sultana N. Nahar, J M. Wadehra

Physics and Astronomy Faculty Research Publications

The differential and total cross sections for the formation of positronium in its ground state from Li and Na atoms by the impact of intermediate-energy positrons are calculated in the first Born and distorted-wave Born approximations. Hellmann-type pseudopotentials are used to represent the alkali-metal ion cores. The difference in the use of pseudopotentials and the static potential for the core representation for evaluating various rearrangement cross sections is discussed.

Thermal And Structural Stability Of Cosputtered Amorphous TaXCu1-X Alloy Thin Films On Gaas, J.E. Oh, John A. Woollam, K.D. Aylesworth, David J. Sellmyer, J.J. Pouch

David Sellmyer Publications

The thermal and chemical stabilities of amorphous-metal diffusion barrier films are of importance in high-temperature semiconductor device applications. The reaction characteristics of the barrier constituents with the surrounding elements as well as the crystallization temperature determine the thermal stability of an amorphous-alloy diffusion barrier. We report that suitable thin films of Ta-Cu have been prepared over a wide range of compositions, by cosputter deposition onto GaAs and fused-quartz substrates. The amorphous nature and crystallization behavior of the films have been monitored by x-ray diffraction and van der Pauw resistivity measurements. Films were found to be amorphous over the range of …

A Criterion For Vortex Breakdown, R. E. Spall, T. B. Gatski, C. E. Grosch

CCPO Publications

A criterion for the onset of vortex breakdown over a wide range of the Reynolds number is proposed. Based upon previous experimental, theoretical, and numerical studies, as well as a new numerical study, an appropriately defined local Rossby number is used to delineate the region where breakdown occurs. Comparisons are made with previously suggested criticality parameters and the unique features of the proposed Rossby number parameter are shown. A number of previous theoretical studies concentrating on inviscid standing‐wave analyses for trailing wing‐tip vortices are reviewed and reinterpreted, along with the previous numerical and experimental studies, in terms of the Rossby …

Errata: First-Principles Theoretical Explanation Of Incommensurate Behavior In Rb2Znc4, V. Katanant, P.J. Edwardson, John Hardy, L. L. Boyer

John R. Hardy Papers

Figures 2(a) and 2(b) of this paper have been inadvertently interchanged; thus, the caption for Fig. 2(a) relates to Fig. 2(b) and the caption for Fig. 2(b) relates to Fig. 2(a).

Exact Evaluation And Recursion Relations Of Two-Center Harmonic Oscillator Matrix Elements, P. J. Drallos, J. M. Wadehra

Physics and Astronomy Faculty Research Publications

Using vibrational wave functions of two relatively displaced harmonic oscillators of arbitrary frequencies, Franck–Condon overlap integrals and matrix elements of x^l, exp(−2cx), and exp(−cx^2) (x is the internuclear separation) are obtained. Useful three‐term, four‐term, and five‐term recursion relations among these matrix elements are derived. It is shown that all of the relevant matrix elements can be obtained from a mere knowledge of the lowest two Franck–Condon overlap integrals. Results are illustrated by computation of Franck–Condon factors for the A ^1∑^+_u –X ^1∑^+_g and the B ^1Π_u –X ^1∑^+_g systems of ^7Li_2.

Calculation Of Electron Capture Cross Sections Of Collisions Of Be ²⁺ On H, A. E. Wetmore, H. R. Cole, Ronald E. Olson

Physics Faculty Research & Creative Works

Using the perturbed stationary state method, including electron translation factors, the authors have calculated electron capture cross sections for the helium-like ions Be²⁺ and B³⁺ incident on ground-state atomic hydrogen. The molecular structure calculation employs pseudo-potentials to represent the inactive K-shell electrons on the incident ions. The calculated cross sections vary rapidly in the 107 cm s-1 velocity range (E approximately 1 keV amu-1). The calculations show preferential transfer to the Be⁺(2s) and the B²⁺(2p) product states. The calculations for B³⁺+H are in good agreement with experimental measurements of Cradall et al …

Determination Of Phenomenological Optical Model Parameters For Neutrons On 208Pb From 4 To 150 Mev, Randy L. Schutt

Masters Theses

Phenomenological o p tic a l model parameters for neutrons incident on ²⁰⁸Pb have been determined for neutron energies from 4 to 150 MeV using the code SNOOPY-8. Neutron total cross sections from 4 to 150 MeV and angular distributions for elastic scattering from 13.5 to 40.0 MeV were utilized. Analyses of total and differential cross sections were performed at a number of energies to determine energy dependent expressions for the real strengths of the central potential, imaginary surface potential, and imaginary volume potential. These energy dependent expressions for V, W_d, and W_S were found to …

Search For The S Meson In Antiproton-Proton Interactions, William J. Fickinger, R. Marino, D. K. Robinson

Faculty Scholarship

The interaction between antiprotons and protons has been studied in the range 1910 to 1990 MeV center-of-mass energy in a drift-chamber experiment at the Brookhaven Alternating Gradient Synchrotron. The total cross section has been determined at eleven different incident momenta, and the elastic cross section between 8 and 30 deg in the laboratory has been measured with an energy resolution of about 5 MeV. The cross section for annihilation into charged mesons has also been measured, with the same resolution. There is no evidence in any of these channels for the existence of a narrow resonance.

Polarizing Beam Splitters For Infrared And Millimeter Waves Using Single-Layer-Coated Dielectric Slab Or Unbacked Films, R. M.A. Azzam

Electrical Engineering Faculty Publications

No abstract provided.

Photorefraction In Batio3, Stephen Ducharme

Stephen Ducharme Publications

This thesis summarizes the results of experimental investigations of the photorefractive properties of melt-grown BaTiO₃ single crystals. Three basic photorefractive material properties are studied: (1) the effective density of photorefractive charges, (2) the photoconductivity of the photorefractive charges, and (3) the relative contributions of electron and hole photoconduction. Volume holographic measurement techniques are used: two-beam energy coupling, four-wave mixing, and erasure of volume holograms. The photorefractive properties were altered experimentally by chemically reducing or oxidizing a BaTiO₃ crystal. I have extended the “hopping conduction” model of photorefractive transport to include simultaneous electron and hole photoconduction. The extension of …

Magnetic Relaxation In Fe-(Sio2) Granular Films, Gang Xiao, Sy_Hwang Liou, A. Levy, J.N. Taylor, C. L. Chien

Sy-Hwang Liou Publications

Magnetic relaxation of granular Fe-(SiO₂) solids with low metal-volume fraction has been studied by employing dc SQUID (superconducting quantum interference device) magnetometry and Mössbauer spectroscopy with the characteristic measuring time differing by nine orders of magnitude. The blocking temperatures (T_B), extrapolated to zero external field as measured by the two techniques maintain a constant ratio of 0.35 independent of samples. Arrhenius law was found adequate in describing the relaxation process, with a well-defined relaxation-time constant of τ₀≃10^-13 sec. A cusp in the susceptibility is observed at T_B, below which irreversible difference …

Double Electron Transitions In Collisions Between Multiply Charged Ions And Helium Atoms, Ronald E. Olson, A. E. Wetmore, M. L. Mckenzie

Physics Faculty Research & Creative Works

A semiclassical model for He is applied to the study of multiply charged ions colliding with He at intermediate energies. Single and double-electron capture and ionisation and capture-ionisation reactions are studied for incident-ion charge states q=+1 to +50 at 1 MeV amu-1. For charge states q>or approximately=+10, single electron capture is found to be dominated by a two-electron transition in which one electron is captured and the other is ionised.

Negative Ion Drift Velocities In Mixtures Of Methane And Sulphur Hexafluoride, M. C. Cornell, Ian M. Littlewood

Physics Faculty Research & Creative Works

The velocities of negative ions drifting in mixtures of methane and Sulphur hexafluoride have been measured. Measurements were made as a function of gas composition, reduced electric field strength between 3 and 185 Td, and total gas pressure in the range 100-600 Torr at 300K. The data indicate that SF 6- (SF6) ions are the dominant ion in all of the gas mixtures studied. Extrapolation of the data using Blanc's Law was used to determine the velocity of Sulphur hexafluoride ions drifting in pure methane.

Photoconductivity Parameters In Lithium Niobate, Robert Gerson, J. F. Kirchhoff, L. E. Halliburton, D. A. Bryan

Physics Faculty Research & Creative Works

Measurements on a variety of doped (magnesium and/or iron) and undoped lithium niobate crystals in the oxidized state demonstrate an Arrhenius dependence of dark conductivity on reciprocal temperature between 460 and 590 K. All of the crystals had roughly the same conductivity and activation energy (1.21 eV) over the temperature range, implying that all have about the same free-carrier concentration and mobility. The enhanced photoconductivity of magnesium-doped lithium niobate is attributed to a greatly reduced trapping cross section of Fe³⁺ for electrons, the smaller cross section being due to a changed substitutional site for Fe³⁺. The Fe …

The Fricke Dosimeter As A 1-Hit Detector, Robert Katz, G. L. Sinclair, M. P. R. Waligorski

Robert Katz Publications

A fit to the experimental data for the response of the Fricke dosimeter to energetic heavy ions is obtained using a calculation of the relative effectiveness of a 1-hit detector, from track theory. We use 2 fitted parameters, the target size, a₀, which may be thought to represent a “diffusion length,” and E₀, the dose of gamma-rays at which there is an average of one hit per target (the D-37 dose), and a new algorithm for the average radial distribution of dose in liquid water from the passing ion. The G value for ions is then …

The Radial Distribution Of Dose Around The Path Of A Heavy Ion In Liquid Water, M. P. R. Waligorski, R. N. Hamm, Robert Katz

Robert Katz Publications

Monte Carlo calculations of the radial distribution of dose in liquid water, incorporating energy deposition due to primary excitations and ionizations, have been performed for protons of energy 1, 10, 20, 50, and 100 MeV. By combining these results with earlier semi-empirical formulae used in track structure theory calculations, a corrected analytic formulation has been developed which on radial integration closely reproduces the value of stopping power for protons in the energy range 0.1–1000 MeV. After including a β-dependent ‘effective charge’ formula, this corrected formulation is tested against all published measurements of radial distribution of dose from energetic ions in …

Beyond The Rigid-Ion Approximation With Spherically Symmetric Ions, L. L. Boyer, M. J. Mehl, J. L. Feldman, John R. Hardy, J. W. Flocken, C. Y. Fong

John R. Hardy Papers

In our recent Letter we introduced an ab initio model for spherically symmetric charge relaxation of ions in a crystal, called potential-induced breathing (PIB), and demonstrated its importance in the calculation of elastic constants. We also investigated the splitting of the longitudinal optic (LO) and transverse optic (TO) mode frequencies, which results from the macroscopic field associated with longitudinal modes. In the discussion immediately before and after Eq. (5) we argued, incorrectly, that the only contributions to the LO-TO splitting from PIB were from terms involving S_k, the derivative of the self-energy of the kth ion with …