Digital Commons Network^™

The Spin‐1 Anisotropic Heisenberg Ferromagnet With Biquadratic Exchange, Harry A. Brown

Physics Faculty Research & Creative Works

No abstract provided.

Resonant Transfer And Excitation: Dependence On Projectile Charge State And Target-Electron Momentum Distribution, J. A. Tanis, E. M. Bernstein, M. W. Clark, W. G. Graham, Robert H. Mcfarland, T. J. Morgan, J. R. Mowat, D. W. Mueller, A. Müller, M. P. Stockli, K. H. Berkner, P. Gohil, R. J. Mcdonald, A. S. Schlachter, J. W. Stearns

Physics Faculty Research & Creative Works

Resonant transfer and excitation (RTE) involving simultaneous electron capture and projectile K-shell excitation has been measured for calcium ions in charge states ranging from neon like to hydrogen like incident on molecular hydrogen over an energy range 100-370 MeV. The results establish a projectile charge-state dependence for RTE and provide a detailed test of theoretical calculations. The effect of the target-electron momentum distribution on the RTE process is demonstrated by comparing with previous results for calcium ions incident on helium. © 1986 The American Physical Society.

Structure In The Energy Dependence Of High-Energy Electron-Capture Cross Sections, W. G. Graham, E. M. Bernstein, M. W. Clark, J. A. Tanis, K. H. Berkner, P. Gohil, R. J. Mcdonald, A. S. Schlachter, J. W. Stearns, Robert H. Mcfarland, T. J. Morgan, A. M̈Ller

Physics Faculty Research & Creative Works

Previous experimental and theoretical work has found electron capture to be a monotonically decreasing function of energy in fast ion-atom collisions. We report here the experimental observation of nonmonotonic behavior of the electron-capture cross sections in fast collisions of calcium ions, in charge states 16+ to 19+, with molecular hydrogen, in the energy range 97368 MeV. The structure observed in the measured cross sections is attributed to the contribution of resonant transfer and excitation to electron capture. © 1986 The American Physical Society.

Tuning Characteristics And New Laser Lines In An Nd:Yap Cw Laser, Laird D. Schearer, Michele Leduc

Physics Faculty Research & Creative Works

We have investigated the CW laser properties of Nd-doped yttrium-aluminum-perovskite (YAP) in a Kr are-lamp, pumped cavity, Seven laser transitions within the 4F3/2-4I11/2 multiplet have been observed. A simple Lyot filter is used to select the particular transitions. The tuning characteristics of the transitions at 1.0745 and 1.0845 μm were also obtained with the addition of a thin, uncoated etalon within the cavity. Tuning widths of 32 and 23 Å, respectively, were obtained. Copyright © 1986 IEEE

Bowen Fluoresence And He Ii Lines In Active Galaxies And Gaseous Nebulae, Hagai Netzer, Moshe Elitzur, Gary J. Ferland

Physics and Astronomy Faculty Publications

We have calculated the intensity of He II and the O III and N III Bowen lines under a variety of astrophysical conditions. Our line-transfer method is based on the escape probability formalism and is especially suitable for combining line fluorescence and photoionization calculations in a simple, straightforward way. It reproduces the results of the more sophisticated line-transfer calculations quite accurately and is much better for producing realistic ionization and thermal structures. An extensive grid of models is presented and discussed, with special emphasis on the case of active galactic nuclei (AGNs). Many O III and N III Bowen lines …

Total Refraction At Oblique Incidence By A Transparent Bilayer Coating On A High-Index Transparent Or Absorbing Substrate, R. M.A. Azzam, Karim Javily

Electrical Engineering Faculty Publications

Transparent bilayer coatings that produce total refraction (TR) of obliquely incident monochromatic light into an underlying substrate are considered. When the substrate is transparent, it is shown that TR takes place without any accompanying change of polarization. Totally refracting bilayers are realizable in the IR where high-refractive-index substrates are available. This is illustrated by a BaF₂–ZnSe bilayer on a Ge substrate at a 10.6-μm (CO₂-laser) wavelength and 45° angle of incidence. Limited changes of the angle of incidence, wavelength, and refractive indices and thicknesses of the two films of the bilayer are introduced, and their effects …

Magnetic Transitions And Scaling Behavior In Gd-Rich Glasses , M.J. O'Shea, David J. Sellmyer

David Sellmyer Publications

The magnetic properties of amorphous alloys with composition Gd_xLa_72-xGa₁₈B₁₀ have been investigated using ac-susceptibilty and dc-magnetization techniques in the temperature range 4.2–300 K. This system shows double-transition behavior for x≳67 and paramagnetic–spin-glass transition behavior for x<67. Time-dependent magnetization effects are present in the spin-glass phase and these effects vanish in finite fields, in qualitative agreement with mean-field theory. The magnetic isotherms around both the paramagnetic-ferromagnetic and ferromagnetic–spin-glass transitions scale according to the scaling hypothesis, and these results are discussed in some detail. A magnetic phase diagram for this system is obtained from the transition temperatures determined from scaling.

Investigation Of Electronic Holography Using Spice Computer Simulation Experiments, Monish Ranjan Chatterjee

Electrical and Computer Engineering Faculty Publications

Using SPICE experiments, it has been possible to verify most of the important aspects of electronic holography. The generation and properties of dynamic echoes under different types of nonlinearities have been extensively tested, and some new information has been garnered in the process. The case of pulse and generalized memory echoes has also been tested, and the results have been fairly satisfactory. Most of all, the simplicity with which the intriguing concept of memory echoes has translated into the circuit implementation on SPICE, and the closeness of the results to predicted behavior have been somewhat of a pleasant surprise.

Since …

Polarization Asymmetry In The Photodisintegration Of The Deuteron, M. P. De Pascale, G. Giordano, G. Matone, D. Babusci, R. Bernabei, Oleksa-Myron Bilaniuk, L. Casano, S. D'Angelo, M. Mattioli, P. Picozza, D. Prosperi, C. Schaerf, S. Frullani, B. Girolami

Physics & Astronomy Faculty Works

The reaction ²(γ,p)n has been studied using a monochromatic and polarized gamma ray beam at energies E(γ)=19.8, 29.0, 38.6, and 60.8 MeV. The beam of an intensity ∼4×10⁵ γ/sec was obtained by Compton back scattering of mode-locked laser light off electron bunches in the Adone storage ring. Photoneutron yields were measured at nine neutron angles thetan≃15, 30, 45, 60, 90, 120, 135, 150, and 165 deg in the center of mass (c.m.) for E(γ)=19.8, 29.0, and 38.6 MeV, and at thetan≃30, 60, 90, 120, and 150 deg c.m. for E(γ)=60.8 MeV. The polarization independent component Iₒ(theta) of the differential cross …

Use Of The Fock Expansion For 1State Wave Functions Of Two-Electron Atoms And Ions, James M. Feagin, Joseph Macek, Anthony F. Starace

Anthony F. Starace Publications

The exact representation of a two-electron wave function near the origin is the Fock expansion, i.e., a double summation over powers of R and of lnR [where R≡(r₁²+r₂²)^1/2] with coefficients dependent on the five remaining angular variables. Using a representation of hyperspherical harmonics, we present here the first numerical solution of the equations for the Fock coefficients. We present also a general procedure for matching a linear combination of Fock-series solutions onto a basis of adiabatic hyperspherical functions at a matching radius R₀. This matching procedure ensures …

Direct Memory Acquisition Of Fast Analog Signals, Syed Javaid Iqbal

Masters Theses

A fast data transfer computer circuit is developed using the direct memory acquisition (DMAC) technique. For this purpose Z-80 microcomputer ·chips, manufactured by Ziolog, were used. The direct memory acquisition circuitry was developed in several stages and required both hardware and software development. An erasable programmable read only memory (EPROM) programmer was built for reading and loading the system program. The design, construction, and testing of the DMAC system are discussed in detail and an example of the use of this system for collecting data is given.

The Design And Construction Of Microprocessor-Computer Controlled Rapid Scanning Fiberoptic Spectrophotometer, Kathleen Marie Tobin

Masters Theses

Conventional spectrophometers require the transfer of a sample to a cuvette for obtaining spectra. The measurement of absorbance in situ can be accomplished using a fiber optic probe which can be placed directly in the sample. The fiber optic probe also minimizes environmental factors such as thermal or vibrational which may affect the absorbing species. A rapid scanning speed allows for essentially simultaneous wavelength monitoring.

The effect of coupling a rapid scanning spectrophotometer with a fiber optic probe provides for an extremely versatile system. When used in comjunction with a microprocessor or computer, this approach offers advantages such as data …

Helium-4 Solid-Liquid Interface Mobility And Ultrasonic Energy Absorption Mechanisms, M. B. Manning, Matthew J. Moelter, C. Elbaum

Physics

The first measurements of acoustic reflection, together with acoustic transmission at the solid-liquid interface of ⁴He, are used to determine the total relative acoustic energy absorption at the interface as a function of temperature. Based on these results, a new mechanism for the temperature dependence of the kinetics of growth and interface mobility is proposed.

(E,2e) Spectroscopic Investigations Of The Spectral Momentum Densities Of Thin Carbon Films, John Robert Dennison

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

An (e,2e) electron scattering spectrometer has been constructed and used for the first time to investigate the spectral momentum density of the valence bands of a solid target. This technique provides fundamental information about the electronic structure of both crystalline and amorphous solids. The three fundamental quantities, the band structure, electron density of states, and electron momentum distribution can be simultaneously derived from the measured (e,2e) cross section.

A review of single electron and (e,2e) scattering theory is given with an emphasis on scattering from solids. The effects of multiple scattering are discussed and a method of deconvoluting those effects …

Absorption Cross-Sections Of Sodium Diatomic Molecules, Zeng-Shevan Fong

Physics Theses & Dissertations

The absorption cross sections of sodium dimers were studied using a heat pipe over operating in the non-heat-pipe mode. Three wavelength regions were observed. They are in the red, the green-blue, and the near ultraviolet regions. The absorption cross section depends on the wavelength of the incident light. Representative peak values for the v"=0 progression in the red and green-blue regions are 2.59 A sup 2 (average value) and 11.77 A sup 2 (T_ave=624 K). The value for the C greater than X transitions is several tenths A sup 2. The cross sections were measured from absorption spectra …

Physics Of Some Environmental Aspects Of Energy, David W. Hafemeister

Physics

Approximate numerical estimates are carried out on the following environmental effects from energy production and conservation: (1) The greenhouse effect caused by increased CO₂ in the atmosphere; (2) Loss of coolant accidents in nuclear reactors; (3) Increased radon concentrations in buildings with very low air infiltration rates; (4) Acid rain from the combustion of fossil fuels; and (5) Explosions of liquified natural gas (LNG).

Energy Conservation In Large Buildings, A. Rosenfeld, David W. Hafemeister

Physics

As energy prices rise, newly energy aware designers use better tools and technology to create energy efficient buildings. Thus the U.S. office stock (average age 20 years) uses 250 kBTU/ft² of resource energy, but the guzzler of 1972 uses 500 (up × 2), and the 1986 ASHRAE standards call for 100–125 (less than 25% of their 1972 ancestors). Surprisingly, the first real cost of these efficient buildings has not risen since 1972. Scaling laws are used to calculate heat gains and losses of buildings to obtain the ΔT(free) which can be as large as 15–30 °C (30–60 °F) for …

A Chronology Of Energy Conservation And Production, David W. Hafemeister

Physics

No abstract provided.

Clayton Et Al. Respond, C.E. Clayton, C. Joshi, C. Darrow, Donald P. Umstadter

Donald Umstadter Publications

Clayton et al. Respond: The authors of the Comment are quite correct when they point out that the ruby-laser scattering system used in our study can only respond to beat-excited density fluctuations with k_y = k₂, where the CO₂ (ruby) beam propagates in the z (y) direction.

The Temporary Capture Of Light By A Dielectric Film, James A. Lock

Physics Faculty Publications

When a wave packet of light passes through a dielectric film it is found that at a transmission maximum, the group velocity of the light wave packet within the film attains its minimum value. Similarly, at a transmission minimum, it is found that the group velocity of the light wave packet within the film attains its maximum value. The measurability of this effect is also discussed.

Investigation Of The Appropriateness Of Sensitized Luminescence To Determine Exciton Motion Parameters In Pure Molecular Crystals, Vasudev M. Kenkre, Paul Ernest Parris, Dankward B. Schmid

Physics Faculty Research & Creative Works

A wealth of experimental data has been collected over the years regarding the sensitized luminescence of molecular crystals. Indeed, such observations have played a primary role in attempts to characterize the dynamical aspects of exciton transport in these materials. Nonetheless, as has been noted previously, serious questions of interpretation remain concerning the relationship between primary experimental observables and microscopic parameters which govern exciton transport and capture. In the past these questions have led to an uncertainty, not always acknowledged, in the values of exciton diffusion constants reported in the literature. On the other hand, careful analysis of some recent experiments …

Temperature Dependence Of The Normal-Metal Aharonov-Bohm Effect, S. Washburn, C. P. Umbach, R. B. Laibowitz, Richard A. Webb

Faculty Publications

The amplitude of h/e periodic oscillations in the magnetoresistance of very small normal-metal (Au) rings, as well as the harmonic h/2e, have been studied as a function of temperature. The amplitudes depend on the temperature T roughly as T-^1/2, as expected from the averaging of conduction channels in the absence of inelastic scattering, but may not be entirely consistent with this model. At the lowest T, the size of the fluctuations in the conductance is about ΔG∼e²/h, as predicted recently.

Ionization Cross Sections For 10-300-Kev/U And Electron-Capture Cross Sections For 5-150-Kev/U 3He2+ Ions In Gases, M. Eugene Rudd, T. V. Goffe, A. Itoh

M. Eugene Rudd Publications

Cross sections for production of positive and negative charge for 10-300-keV/u He²⁺ ions on He, Ne, Ar, Kr, H₂, N₂, CO, O₂, CH₄, N₂O, and C0₂ were measured by the transverse-field method. Single- and double-electron-capture cross sections at 5-150 keV/u for the same targets were measured by the method of deflection of different charge-state components of the beam after passing through a known length of target gas. A secondary-emission detector was used to detect the neutral component of the beam. A small least-squares adjustment of the cross sections …

Electron Production In Proton Collisions: Total Cross Sections, M. Eugene Rudd, Y-K. Kim, D. H. Madison, J. W. Gallagher

M. Eugene Rudd Publications

Existing data on the ionization of neutral atoms and molecules by proton impact are reviewed, and electron production cross-section data are collected. The three major experimental methods are discussed and possible sources of error identified. Some theoretical cross sections are discussed, and well-established methods of relating them to measured cross sections are reviewed. A mathematical equation is fitted to the weighted experimental data for each target, and these fits are adjusted to be consistent with appropriate theoretical calculations and with electron impact and photoionization data. Recommended values of total cross sections for proton-impact ionization are given.

Electron Production In Proton Collisions: Total Cross Sections, M. Eugene Rudd, Yongki Kim, Don H. Madison, Jean W. Gallagher

Physics Faculty Research & Creative Works

Existing data on the ionization of neutral atoms and molecules by proton impact are reviewed, and electron production cross-section data are collected. The three major experimental methods are discussed and possible sources of error identified. Some theoretical cross sections are discussed, and well-established methods of relating them to measured cross sections are reviewed. A mathematical equation is fitted to the weighted experimental data for each target, and these fits are adjusted to be consistent with appropriate theoretical calculations and with electron impact and photoionization data. Recommended values of total cross sections for proton-impact ionization are given.

Angular Differential Cross Sections For The Excitation Of 11S Helium To The 21S And 21P States By 25- To 100-Kev-Proton Impact, T. J. Kvale, D. G. Seely, D. M. Blakenship, E. Redd, Timothy J. Gay, M. Kimura, E. Rille, J. L. Peacher, J. T. Park

Timothy J. Gay Publications

Angular differential cross sections for the proton-impact excitation of ground-state helium (1¹S) to the 2¹S and 2¹P states have been measured for the first time in the energy range 25 to 100 keV with use of the energy-loss technique. The data indicate that, for very small scattering angles, at 25 keV the 2¹S differential cross section is greater than the 2¹P differential cross section. For impact energies greater than 50 keV, the 2¹P differential cross section clearly dominates over the 21S cross section in the very small scattering …

Time-Dependent Magnetic Structures Of The Superconducting Mixed Ternary System Ho(Rh₁₋ₓirₓ)₄B₄, Steven E. Lambert, M. Brian Maple, Oran Allan Pringle, Herbert A. Mook

Physics Faculty Research & Creative Works

Magnetic structures have been determined by netron diffraction for several compositions in the superconducting mixed ternary system Ho(Rh_1-xIr_x)₄B₄. Two features previously reported to occur in the heat capacity for some compositions are shown to correspond to successive magnetic transitions. For x=0.30 and 0.45, neutron diffraction peaks for the lowest temperature structure develop over a timescale of many hours. The results are discussed in terms of magnetic frustration.

Angular Differential Cross Sections For The Excitation Of 1¹S Helium To The 2¹S And 2¹P States By 25- To 100-Kev-Proton Impact, Thomas J. Kvale, Denver G. Seely, D. M. Blankenship, E. Redd, Timothy Gay, Mineo Kimura, Eduard P. Rille, Jerry Peacher, John T. Park

Physics Faculty Research & Creative Works

Angular differential cross sections for the proton-impact excitation of ground-state helium (1¹S) to the 2¹S and 2¹P states have been measured for the first time in the energy range 25 to 100 keV with use of the energy-loss technique. The data indicate that, for very small scattering angles, at 25 keV the 2¹S differential cross section is greater than the 2¹P differential cross section. For impact energies greater than 50 keV, the 2¹P differential cross section clearly dominates over the 2¹S cross section in the very …

A Variation-Perturbation Method For Atomic And Molecular Interactions. Ii. The Interaction Potential And Van Der Waals Molecule For Ne–Hf, Gordon A. Gallup, J. Gerratt

Gordon Gallup Publications

A recently developed variation-perturbation theory for calculating intermolecular forces has been applied to the Ne–HF system for fixed H–F distances. The maximum well depth is 0.49 kJ/mol (41 cm^-1) for a linear configuration with the H between the Ne and F and the Ne–H distance approximately 5.5 bohr. A secondary minimum of depth 0.24 kJ/mol (20 cm^-1) was found for the other linear configuration at a Ne–F distance of about 7.0 bohr. A saddle point, about 0.20 kJ/mol (17 cm^-1) deep, for the T-shaped configuration is present also at about 7.0 bohr. The potential …

A Variation-Perturbation Method For Atomic And Molecular Interactions. I. Theory, Gordon A. Gallup, J. Gerratt

Gordon Gallup Publications

We have developed a variation-perturbation procedure for calculating intermolecular forces. It is based on the valence bond method of constructing wave functions and involves a number of interlocking techniques and approximations that are justified by the small size of the interaction potential relative to the total energy. In this article we give an outline of the theory of our technique. We have used this procedure to determine the potential between a Ne atom and a rigid HF molecule. The results of this calculation are given in the next article. The Journal of Chemical Physics is copyrighted by The American Institute …