Physical Sciences and Mathematics Commons^™

Review Of Verification And Compliance: A Problem Solving Approach By Michael Krepon & Mary Umberger, Toward A Comprehensive Test Ban By Steve Fetter, And Making Space Defense Work: Must The Superpowers Cooperate? By A. Fenner Milton, M. Scott Davis, & John Parmentola, David W. Hafemeister

Physics

No abstract provided.

Doubly Differential Detachment Cross Sections For Fast H-–Rare-Gas Collisions, Chih-Ray Liu, Anthony F. Starace

Anthony F. Starace Publications

Detailed theoretical analyses are presented of the projectile-energy dependence as well as the target dependence of the electron-detachment collision processes, H^-+T→H(n=2)+T*+e^-. These analyses are illustrated by calculations of both projectile-frame and laboratory-frame doubly differential cross sections (DDCS’s) for 0.5-, 1.0-, and 1.5-MeV H^- collisions with He targets and for 0.5-MeV H^- collisions with Ne, Ar, Kr, and Xe targets; in addition, we present laboratory frame DDCS’s for 0.1-MeV H^- collisions with Xe targets. Comparisons with available experimental data are given.

Possible Conserved Quantity For The Henon-Heiles Problem, Paul Finkler, C. Edward Jones, Glenn A. Sowell

Paul Finkler Papers

We study a power-series expansion for a conserved quantity K in the case of the two-dimensional Henon-Heiles potential. An alternative technique to that of Gustavson [Astron. J. 71, 670 (1966)] is applied to find the coefficients in the expansion for K. The technique is used to determine twelve orders for the conserved quantity K, more than twice as many as that calculated by Gustavson. We investigate the degree of constancy of our truncated K in regions where the motion is known to be chaotic and also where it is nonchaotic.

Theory Of Light Scattering By A Nonequilibrium Binary Mixture, J.C. Nieuwoudt, B.M. Law

Faculty Publications

A binary mixture subject to a large temperature gradient is studied. Solutions of the evolution equations for the time-dependent fluctuation correlations are obtained using mode-coupling theory subject to the assumption that the mixture is not close to a critical point. From these results predictions for the light-scattering spectrum at the Rayleigh and Brillouin lines are made. The temperature gradient is shown to cause a large enhancement of the scattering amplitude at the Rayleigh line, whereas the effect at the Brillouin line is found to be small.

Intracavity Frequency Doubling Of A Nd:Yag Laser With An Organic Nonlinear Optical Crystal, Stephen Ducharme, W.P. Risk, W.E. Moerner, Victor Y. Lee, R.J. Twieg, G.C. Bjorklund

Stephen Ducharme Publications

Your access to Appl. Phys. Lett. is provided through the subscription of Univ Nebraska-Lincoln Lib. What is this? Scitation Citing Articles | CrossRef Citing Articles | All Citing Articles [ Previous / Next Abstract | Issue Table of Contents | Bottom of Page ] Applied Physics Letters -- August 6, 1990 -- Volume 57, Issue 6, pp. 537-539 Full Text: [ PDF (639 kB) ] Order Rightslink Permissions for Reuse About Rightslink view MyArticles What is this? Select up to 20 articles at a time. Intracavity frequency doubling of a Nd:YAG laser with an organic nonlinear optical crystal Stephen Ducharme, …

Analytic Solutions For Three-State Systems With Overlapping Pulses, C. E. Carroll, Foek T. Hioe

Physics Faculty/Staff Publications

Two classes of analytic solutions for three-state systems involving two overlapping laser pulses of different shapes, or of similar shapes but with their centers displaced, are presented. We find a remarkable connection between the order of arrival of the two overlapping pulses and the effectiveness of transfer from the ground state to the third state, and we find remarkable results for the maximum occupation probability of the intermediate state. The approach of these analytic solutions to the adiabatic-following process is also demonstrated.

Measurement Of Parity Violation In The Elastic Scattering Of Polarized Electrons From 12C, P. A. Souder, R. Holmes, D. - H. Kim, K. S. Kumar, M. E. Schulze, K. Isakovich, G. W. Dodson, K. W. Dow, M. Farkhondeh, S. Kowalski, M. S. Lubell, J. Bellanca, M. Goodman, S. Patch, Richard Wilson, G. D. Cates, S. Dhawan, Timothy J. Gay, V. W. Hughes, A. Magnon, R. Michaels, H. R. Schaefer

Timothy J. Gay Publications

We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from ¹²C nuclei. Our result is A_expt=0.60±0.14±0.02 ppm, where the first error is statistical and the second is systematic. With a beam polarization of 0.37, we compute the isoscalar vector hadronic coupling constant γ̃ to be 0.136±0.032±0.009. The standard model predicts γ̃ =0.155 at the tree level, in agreement with our data.

A Simulation Of A Multi-Hop Communications Network Using A Kinematic Topology Generator And Static Sphere-Packing Power Control, Kevin Charles Davis

Masters Theses

No abstract provided.

Anomalous Hall-Effect Results In Low-Temperature Molecular-Beam-Epitaxial Gaas - Hopping In A Dense El2-Like Band, David C. Look, D. C. Walters, M. O. Manasreh, J. R. Sizelove, C. E. Stutz, K. R. Evans

Physics Faculty Publications

Molecular-beam-epitaxial GaAs grown at very low temperatures (∼200 °C) exhibits anomalous Hall-effect properties. Here we show conclusively that the room-temperature conduction is due to activated (nearest-neighbor) hopping in a deep defect band of concentration 3×10¹⁹ cm^-3, and energy E_c-0.75 eV, along with conduction due to free carriers thermally excited from this band. At low measurement temperatures, variable-range hopping [σ∝exp(-T₀/T)^1/4] prevails. The conduction-band mobility can be well explained by neutral-deep-donor scattering in parallel with lattice scattering.

Magnetic Polarity Fractions In Magnetotactic Bacterial Populations Near The Geomagnetic Equator, F. F. Torres De Araujo, F. A. Germano, L. L. Goncalves, M. A. Pires, Richard B. Frankel

Physics

The relative numbers of North-seeking and South-seeking polarity types in natural populations of magnetotactic bacteria were determined at sites on the coast of Brazil. These sites were South of the geomagnetic equator and had upward geomagnetic inclinations of 1–12°. For upward inclinations >6°, South-seeking cells predominated over North-seeking cells by more than a factor of 10. For upward inclinations

Argon-Photoion–Auger-Electron Coincidence Measurements Following K-Shell Excitation By Synchrotron Radiation, Jon C. Levin, C. Biedermann, N. Keller, L. Liljeby, C.-S. O, R. T. Short, Ivan A. Sellin, Dennis W. Lindle

Chemistry and Biochemistry Faculty Research

Argon photoion spectra have been obtained for the first time in coincidence with K-LL and K-LM Auger electrons, as a function of photon energy. The simplified charge distributions which result exhibit a much more pronounced photon-energy dependence than do the more complicated noncoincident spectra. In the near-K-threshold region, Rydberg shakeoff of np levels, populated by resonant excitation of K electrons, occurs with significant probability, as do double-Auger processes and recapture of the K photoelectron through postcollision interaction.

Double Excitation Of He By Fast Ions, J. P. Giese, Michael Schulz, J. K. Swenson, Harald Schone, Malika Benhenni, S. L. Varghese, Charles Randy Vane, Peter F. Dittner, Stephen M. Shafroth, Sheldon Datz

Physics Faculty Research & Creative Works

Autoionization of He atoms following double excitation by electrons, protons, C^Q+ (Q=4-6), and F^Q+ (Q=7-9) ions has been studied. The electron-emission yields from the doubly excited 2s²(¹S), 2s2p(¹P), and 2p²(¹P) states were measured at the reduced projectile energy of 1.5 MeV/nucleon for observation angles between 10°and 60°. The results indicate excitation to the 2s²(¹S) and 2p²(¹D) states increases as approximately Q³, while excitation to the 2s2p(¹P) state varies as approximately Q², where Q is …

Random-Field Blume-Capel Model: Mean-Field Theory, Miron Kaufman, M. Kanner

Physics Faculty Publications

The global phase diagram of the Blume-Capel model in a random field obeying the bimodal symmetric distribution is determined by using the mean-field method. The phase diagram includes an isolated ordered critical end point and two lines of tricritical points. A new phase emerges for strong enough random fields: the ferromagnetic-nonmagnetic phase. It is argued that such a phase occurs in three dimensions.

Effects Of Quantum Noise On A Two-Level System In A Single-Mode Cavity, Linda L. Vahala

Electrical & Computer Engineering Faculty Publications

The effects of quantum noise on a two-level system in the bad-cavity regime are considered perturbatively in the form of closure at the pair-correlation level. It is found that pair-correlation effects can reduce the level of semiclassical chaos. However, under the rotating-wave approximation (RWA), quantum noise can lead to chaos if there is an initial population inversion, while the full RWA Hamiltonian system remains integrable.

32nd Rocky Mountain Conference

Rocky Mountain Conference on Magnetic Resonance

Program and registration information for the 32nd annual meeting of the Rocky Mountain Conference, co-sponsored by the Rocky Mountain Section of the Society for Applied Spectroscopy and the Rocky Mountain Chromatography Discussion Group. Held in Denver, Colorado, July 29 - August 3, 1990.

Interference Enhancement Of The Internal Fields At Structural Scattering Resonances Of A Coated Sphere, James A. Lock

Physics Faculty Publications

We examine the interior electromagnetic energy density of a coated nonabsorbing sphere at a number of scattering resonances. As is the case for an uncoated sphere, the interior energy density becomes large at the a^p_l and b^p_l resonances. It becomes especially large for p - 1 values of the coating thickness at resonance. These p - 1 enhancements are analogous to the interference maxima that occur in the intensity reflectance of two thin films in contact.

Chemical And Reconstruction Induced Surface Core-Level Shifts: H On Low-Index W Surfaces, D. Mark Riffe, G. K. Wertheim, P. H. Citrin

All Physics Faculty Publications

The H-induced shift of the surface-atom core-level binding energy in W(110) is shown to arise from two distinct effects, one chemical in nature and the other structural. The structural shift supports a recently proposed (1p×1) reconstruction that turns on at ∼0.5 monolayer coverage. These new findings are used to provide a self-consistent interpretation of previously reported shifts from H-covered W(111) and W(100) surfaces.

Transverse Electrodisintegration Of The Deuteron In The Threshold Region At High Q2,", R G. Arnold, D Benton, P E. Bosted, L Clogher, B Debebe, M B. Frodyma, R S. Hicks, A Hotta, Gerald Alvin Peterson

Gerald Alvin Peterson

Cross sections for 180° deuteron electrodisintegration have been measured near threshold for the Q2 range 1.21 to 2.77 (GeV/c)2. The data are compared to several nonrelativistic meson-nucleon and hybrid quark-hadron models. The data are in strong disagreement with the impulse approximation, indicating the importance of non-nucleonic degrees of freedom. None of the models are in good agreement with the data at all values of Q2. The ratio W1/W2 of inelastic structure functions has been extracted using previous forward angle data and is found to decrease strongly near threshold, also indicating the importance of interaction effects.

Measurements Of The Deuteron And Proton Magnetic Form Factors At Large Momentum Transfers, P E. Bosted, A T. Katramatou, R G. Arnold, D Benton, L Clogher, G De Chambrier, J Lambert, A Lung, G G. Petratos, A Rahbar, S E. Rock, Z M. Szalata, B Debebe, M Frodyma, R S. Hicks, A Hotta, Gerald Alvin Peterson, R A. Gearhart, J Alster, J Lichtenstadt, F Dietrich, K Van Bibber

Gerald Alvin Peterson

Measurements of the deuteron elastic magnetic structure function B(Q') are reported at squared four-momentum transfer values 1.20~ Qi ~ 2.77 (GeV/c)'. Also reported are values for the proton magnetic form factor Gstr(Q2) at 11 Q values between 0.49 and 1.75 (GeV/c) . The data were obtained using an electron beam of 0.5 to 1.3 GeV. Electrons backscattered near 180' were detected in coincidence with deuterons or protons recoiling near 0 in a large solid-angle double-arm spectrometer system. The data for B(Q ) are found to decrease rapidly from Q =1.2 to 2 (GeV/c), and then rise to a secondary maximum …

Reduced Form For Coulomb-Wave Multicenter Integrals, Jack C. Straton

Physics Faculty Publications and Presentations

In a previous paper [J. C. Straton, Phys. Rev. A 41, 71 (1990)] an integro-differential transform was introduced and utilized to obtain the analytically reduced form for multicenter integrals composed of general-state hydrogenic orbitals, Yukawa or Coulomb potentials, and plane waves. The present paper extends this result to include Coulomb waves.

Observation Of Velocity-Tuned Multiphoton Doppleron Resonances In Laser-Cooled Atoms, Jeffrey J. Tollett, Jian Chen, J. Greg Story, N. W M Ritchie, Curtis C. Bradley, Randall G. Hulet

Physics Faculty Research & Creative Works

An atomic beam of Li was transversely cooled using an intense standing-wave radiation field. A dramatic change in the transverse velocity distribution was observed. Structure in the resulting velocity distribution was found to be due to velocity-tuned multiphoton Doppleron resonances. The force due to seven-photon resonances is clearly resolved in the data. The data are in good agreement with theoretical predictions.

A Mathematical Model Of The Dynamics Of An Optically Pumped Codoped Solid State Laser System, Thomas G. Wangler

Mathematics & Statistics Theses & Dissertations

This is a study of a mathematical model for the dynamics of an optically pumped codoped solid state laser system. The model comprises five first order, nonlinear, coupled, ordinary differential equations which describe the temporal evolution of the dopant electron populations in the laser crystal as well as the photon density in the laser cavity. The analysis of the model is conducted in three parts.

First, a detailed explanation of the modeling process is given and the full set of rate equations is obtained. The model is then simplified and certain qualitative properties of the solution are obtained.

In the …

An Artificial Neural Approach To The Decomposition Problem, Chandrashekar L. Masti

Electrical & Computer Engineering Theses & Dissertations

The goal of this thesis is to develop an artificial neural approach toward addressing the intractability involved with the decomposition problem. The search for the lattice of substitution property (s. p.) partitions essential to decompositions is cast into the framework of constraint satisfaction. An artificial neural network is developed to provide solutions by performing optimization of a mathematically derived objective function over the problem space. The issue of transitivity is verified to belong to a class of problems beyond the scope of solvability for conventional quadratic-order constraint satisfaction neural networks. A theorem is stated and proved establishing that third-order correlations …

The Study Of Oxygen Transport Through Polycrystalline, Single Crystal And Alloyed Silver, Dongchuan Wu

Physics Theses & Dissertations

The permeation of oxygen through large grain polycrystalline silver, through the (110), (111) and (100) single crystals of silver and through Ag0.05Zr alloy have been studied over the temperature range of 400 - 800 °C. In addition, studies were also conducted using glow discharge dissociation of the supply side ( upstream ) molecular oxygen in order to examine whether normal dissociative adsorption is a limiting step in the overall transport process.

The permeability of oxygen through polycrystalline silver was found to be quite linear and quite repeatable. The diffusivity measurements were found to exhibit two distinct linear regions, one above …

On The Electrochemical Etching Of Tips For Scanning Tunneling Microscopy, Nancy Burnham, J. Ibe, P. Bey Jr., S. Brandow, R. Brizzolara, D. Dilella, K. Lee, C. K. Marrian, R. Colton

Nancy A. Burnham

The sharpness of tips used in scanning tunneling microscopy(STM) is one factor which affects the resolution of the STM image. In this paper, we report on a direct‐current (dc) drop‐off electrochemicaletching procedure used to sharpen tips for STM. The shape of the tip is dependent on the meniscus which surrounds the wire at the air–electrolyte interface. The sharpness of the tip is related to the tensile strength of the wire and how quickly the electrochemical reaction can be stopped once the wire breaks. We have found that the cutoff time of the etch circuit has a significant effect on the …

Photodarkening Profiles And Kinetics In Chalcogenide Glasses, Stephen Ducharme, J. Hautala, P.C. Taylor

Stephen Ducharme Publications

The spatial and temporal evolution of photodarkening in chalcogenide glasses is simulated by a simple kinetic model and tested against experiments. In the model, photodarkening, a gradual decrease of the energy of the absorption edge caused by above-band-gap illumination, is the additional absorption at defects created by the absorbed light. The defect-creation rate is proportional to the rate at which photons are absorbed either directly at the defect site or, alternatively, at a neighboring site. The depletion of the incident light within the sample is included and the resulting equations cast into a universal form that is applicable to realistic …

Kerr Effect Of Two-Medium Layered Systems, Liang-Yao Chen, William A. Mcgahan, Z.S. Shan, David J. Sellmyer, John A. Woollam

David Sellmyer Publications

Detailed and practical expressions are given for the magneto-optical Kerr effect (MOKE) for various configurations of two media. One is a magneto-optic (MO) one, and the other is a nonmagnetic (NM) medium. For a system of two thick media with a single interface, with a first-order approximation in MOKE term Q, the Kerr function is determined by the product of a MOKE term Q and an optical term η. A second type of system includes a thin MO (or NM) layer deposited on a thick NM (or MO) substrate. For a MO/(NM-substrate) configuration, the Kerr function is related to …

Universal Scaling Of Nonlocal And Local Resistance Fluctuations In Small Wires, H. Haucke, S. Washburn, A. D. Benoit, C. P. Umbach, Richard A. Webb

Faculty Publications

Resistance fluctuations in small metal samples result from coherent transport of the carriers. The wave functions of the carriers extend into regions which are not accessible classically. We have directly measured the length dependence of the nonlocal magnetoresistance fluctuations in Sb and Au wires by studying regions of our samples separated from the classical current path by a distance L which varied from 3L_cphi down to 0.2L_cphi (where L_cphi is the phase coherence length for the carriers in the metal). These fluctuations decay exponentially with L/L_cphi. Measurements along the classical current paths scale more slowly …

Observation Of Ballistic Phonons In Silicon Crystals Induced By Α Particles, Betty A. Young, Blas Cabrera, Adrian T. Lee

Physics

We have observed the ballistic-phonon-focusing pattern along the [100] axis of a 1-mm-thick silicon crystal using α-particle bombardment as the phonon source. These experiments on phonon-mediated particle detection are performed in vacuum at about 400 mK and use titanium-superconducting-transition-edge phonon sensors on the crystal surfaces. The ballistic time of flight is confirmed in one experiment and the focusing patterns are spatially resolved in another. These data indicate that about 1/3 of the phonon energy striking the back face during the first μsec is ballistic.

Review Of Atoms For Peace And War, 1953-1961: Eisenhower And The Atomic Energy Commission By Richard G. Hewlett And Jack M. Holl, David W. Hafemeister

Physics

No abstract provided.