Digital Commons Network^™

Strong Velocity Dependence Of Electron Capture In Collisions Between Aligned Na*(3p) And He2+, A. R. Schlatmann, R. Hoekstra, R. Morgenstern, Ronald E. Olson, J. Pascale

Physics Faculty Research & Creative Works

By analyzing spectra of emitted photons, we have studied state-selective electron capture in collisions of He²⁺ on aligned Na*(3p) atoms that span the "velocity-matching" energy between projectile and target electron. We find a strong dependence of the capture cross sections on the Na*(3p) orbital alignment, i.e., aligned perpendicular or parallel to the ion beam direction. The preference changes from perpendicular to parallel at a velocity close to the classical orbital velocity of the 3p electron. Classical-trajectory Monte Carlo calculations reproduce this striking energy dependence. © 1993 The American Physical Society.

Azimuthal Angular Dependence Of Recoil-Ion And Electron Emission In 0.5-Mev P + He Collisions, R. Dörner, J. Ullrich, Ronald E. Olson, O. Jagutzki, H. Schmidt-Böcking

Physics Faculty Research & Creative Works

Measurements and n-body classical-trajectory Monte Carlo calculations are presented for the dependence of recoil-ion emission on the azimuthal angle between a projectile and a recoil ion. From the measured momenta of the projectile and the recoil ion, the dependence of the electron emission on the azimuthal angle between projectile and electron is deduced. The recoil ions are found to be emitted to the opposite direction of the scattered projectile only for scattering angles larger than 1 mrad, while for smaller scattering angles, the momentum of the emitted electron results in a broad azimuthal angular distribution of the recoil ions. For …

Direct Measurements Of The Transport Of Nonequilibrium Electrons In Gold Films With Different Crystal Structures, T. Juhasz, H. E. Elsayed-Ali, G. O. Smith, C. Suárez, W. E. Bron

Electrical & Computer Engineering Faculty Publications

The transport of femtosecond-laser-excited nonequilibrium electrons across polycrystalline and single-crystalline gold films has been investigated through time-of-flight measurements. The thicknesses of the films range from 25 to 400 nm. Ballistic electrons as well as electrons interacting with other electrons and/or with the lattice have been observed. The ballistic component dominates the transport in the thinner films, whereas the interactive transport mechanism is dominant at the upper end of the thickness range. A slower effective velocity of the interactive component is observed in the polycrystalline samples, and is assumed to arise from the presence of grain boundaries. The reflection coefficient of …

Absolute-Convective Instabilities And Their Associated Wave Packets In A Compressible Reacting Mixing Layer, F. Q. Hu, T. L. Jackson, D. G. Lasseigne, C. E. Grosch

Mathematics & Statistics Faculty Publications

In this paper the transition from convective to absolute instability in a reacting compressible mixing layer with finite rate chemistry is examined. The reaction is assumed to be one step, irreversible, and of Arrhenius type. It is shown that absolute instability can exist for moderate heat release without backflow. The effects of the temperature ratio, heat release parameter, Zeldovich number, equivalence ratio, direction of propagation of the disturbances, and the Mach number on the transition value of the velocity ratio are given. The present results are compared to those obtained from the flame sheet model for the temperature using the …

A Numerical Study Of Wave Propagation In A Confined Mixing Layer By Eigenfunction Expansions, Fang Q. Hu

Mathematics & Statistics Faculty Publications

It is well known that the growth rate of instability waves of a two-dimensional free shear layer is reduced greatly at supersonic convective Mach numbers. In previous works, it has been shown that new wave modes exist when the shear layers are bounded by a channel due to the coupling effect between the acoustic wave modes and the motion of the mixing layer. The present work studies the simultaneous propagation of multiple stability waves using numerical simulation. It is shown here that the coexistence of two wave modes in the flow field can lead to an oscillatory growth of disturbance …

Induced Mach Wave-Flame Interactions In Laminar Supersonic Fuel Jets, F. Q. Hu, T. L. Jackson, D. G. Lasseigne, C. E. Grosch

Mathematics & Statistics Faculty Publications

A model problem is proposed to investigate the steady response of a reacting, compressible laminar jet to Mach waves generated by wavy walls in a channel of finite width. The model consists of a two-dimensional jet of fuel emerging into a stream of oxidizer which are allowed to mix and react in the presence of the Mach waves. The governing equations are taken to be the steady parabolized Navier-Stokes equations which are solved numerically. The kinetics is assumed to be a one-step, irreversible reaction of the Arrhenius type. Two important questions on the Mach wave-flame interactions are discussed: (i) how …

Monte Carlo Director Modeling And Display, Using The Cern Laboratory, Christine A. Byrd, Charles M. Byrd, Wilfred J. Braithwaite

Journal of the Arkansas Academy of Science

Detectors for high energy nuclear physics experiments are being modeled using programs developed and maintained at CERN, the European Organization for Nuclear Research. These programs include data handling and display routines, as well as those using random-sampling Monte Carlo techniques to calculate energy depositions for high energy particles as they pass through the various parts of the detector system. The complete CERN library has been imported for use with our Workstation computers in a multiple user environment. The enormous CERN Monte Carlo program GEANT(French for GIANT) tracks the progress of a particle through a detector on a simulated event-by-event basis. …

User-Interface Coding For The Cern/Geant Nuclear Physics Program, David L. Roetzel, Wilfred J. Braithwaite

Journal of the Arkansas Academy of Science

Explanations will be given of the various user-written routines required by the Monte Carlo detector-modeling program GEANT, developed by CERN, the European Organization for Nuclear Research. User-written routines must be linked with the CERN library to accomplish the researcher's intentions. Examples will illustrate how GEANT passes information to subprograms needed to model events. Various data structures used by GEANT library calls and included in each user routine, are similarly illustrated. Both computational-speed and memory-size limitations need to be factored into the construction of a simulation model. This will constrain the calls used in the user-written routines. Examples are provided of …

Pairwise And Many-Body Contributions To Interaction Potentials In He(N) Clusters, Carol A. Parish, Clifford E. Dykstra

Chemistry Faculty Publications

High level ab initio calculations have been carried out to assess the pairwise additivity of potentials in the attractive or well regions of the potential surfaces of clusters of helium atoms. A large basis set was employed and calculations were done at the Brueckner orbital coupled cluster level. Differences between calculated potentials for several interacting atoms and the corresponding summed pair potentials reveal the three‐body and certain higher order contributions to the interaction strengths. Attraction between rare gas atoms develops from dispersion, and so helium clusters provide the most workable systems for analyzing nonadditivity of dispersion. The results indicate that …

High-Energy Behavior Of The Double Photoionization Of Helium From 2 To 12 Kev, Jon C. Levin, Ivan A. Sellin, B. M. Johnson, Dennis W. Lindle, R. D. Miller, Y. Azuma, H. G. Berry, D.-H. Lee, N. Berrah

Chemistry and Biochemistry Faculty Research

We report the ratio of double-to-single photoionization of He at several photon energies from 2 to 12 keV. By time-of-Aight methods, we find a ratio consistent with an asymptote at 1.5%±0.2%, essentially reached by h v≈4 keV. Fair agreement is obtained with older shake calculations of Byron and Joachain [Phys. Rev. 164, 1 (1967)], of Aberg [Phys. Rev. A 2, 1726 (1970)], and with recent many-body perturbation theory (MBPT) of Ishihara, Hino, and McGuire [Phys. Rev. A 44, 6980 (1991)]. The result lies below earlier MPBT calculations by Amusia et al. [J. Phys. B 8 …

Temporal Development Of Electric Field Structures In Photoconductive Gaas Switches, K. H. Schoenbach, J. S. Kenney, F.E. Peterkin, R. J. Allen

Bioelectrics Publications

The temporal development of the electric field distribution in semi‐insulating GaAs photoconductive switches operated in the linear and lock‐on mode has been studied. The field structure was obtained by recording a change in the absorption pattern of the switch due to the Franz–Keldysh effect at a wavelength near the band edge of GaAs. In the linear mode, a high field layer develops at the cathode contact after laser activation. With increasing applied voltage, domainlike structures become visible in the anode region and the switch transits into the lock‐on state, a permanent filamentary electrical discharge. Calibration measurements show the field intensity …

Electromagnetism, Yimin Wang, Clifton Keller

All Books

No abstract provided.

Sign Correlations And The Mechanism For Parity Violation, Vladimir Gudkov

Faculty Publications

The problem of possible sign correlations of P-odd effects due to parity mixing on the compound nuclear stage is discussed. For an unambiguous test of the conventional model of parity violation on the compound nuclear stage, it is not enough only to measure the sign correlation of P-odd effects on some resonances, but it is necessary also to know the neutron decay amplitudes for each resonance.

Multimedia - Hype Or No?, Robert Fuller

Robert G. Fuller Publications

Commonly, multimedia is used as a modern name for interactive video. It simply means using a computer to control the presentation of video images to an audience. It facilitates glitzy presentations of boring data. In my view, this is hype.

However, there is a more profound sense of the term. Multimedia can be seen in an historical context that places it in the tradition that began with Vannevar Bush, director of the U.S. Office of Scientific Research and Development, who in 1945 published an article, "As We May Think" in the Atlantic Monthly. In that article he suggested a "future …

Electric-Field Stabilization And Competition Of Gratings In A Photorefractive Polymer, Stephen Ducharme, Brian Jones, James M. Takacs, Lei Zhang

Stephen Ducharme Publications

We report observations of electric-field stabilization of gratings and grating competition in a new photorefractive polymer mixture composed of 40 wt. % diethylamino-benzaldehyde-diphenyl hydrazone dissolved in Bisphenol A 4,4'-nitroaminotolane. Gratings formed with a 650-nm optical wavelength in 145-μm-thick films at 138-kV/cm bias field have a diffraction efficiency as high as 0.11%, require an energy density of –1 J/cm² for formation, and show cancellation, revelation, and electric-field-stabilized persistence. We propose a model in which fast recording is associated with one set of photosensitive traps, whereas a slower cancellation and subsequent revelation are associated with a competing grating formed …

A Model Of Cell Damage In Space Flight, Robert Katz, F. A. Cucinotta, J. W. Wilson, J. L. Shinn, Duc M. Ngo

Robert Katz Publications

Cell damage by high LET radiations has been described by a phenomenological model (track theory) for 20 years and more. Molecules of biological significance (dry enzymes and viruses) act as 1 hit detectors. Recent additions to the class of I-hit detectors are E. Coli B, and the creation of both single and double strand breaks in SV-40 virus in EO buffer, where indirect effects predominate. The response of cells (survival, transformation, chromosome aberration) to these radiations is typically described by a 4-parameter model whose numerical values are determined by fitting the equations of the theory to experimental data at high …

The Development Of A Solar Radiation Extinction Correction For Satellite Data, Widad I. Mohamed

Electronic Theses and Dissertations

The main objectives of this thesis are the following: 1) Remove the haze using water surfaces in Landsat satellite imagery of the visible and near-infrared regions for their properties of high absorption of solar radiation and weak reflection of it. The scattered solar radiation is most obvious in dark weakly reflecting regions such as water. The haze removal technique depends on subtraction of scattered light from picture elements within the satellite imagery. 2) Derive a formula and techniques for a given image to correct for extinction by transforming the observed intensity of the signal transmitted to the Landsat detector to …

Determination Of The Neutron Spin Structure Function, P. L. Anthony, R. G. Arnold, H. R. Band, H. Borel, P.E. Bosted, V. Breton, G. D. Cates, T. E. Chupp, F. S. Dietrich, J. Dunne, R. Erbacher, J. Fellbaum, H. Fonvielle, R. Gearhart, R. Holmes, E. W. Hughes, J. R. Johnson, D. Kawall, C. Keppel, S. E. Kuhn, R. M. Lombard-Nelsen, J. Marroncle, T. Maruyama, W. Meyer, Z. E. Meziani, H. Middleton, J. Morgenstern, N. R. Newbury, G. G. Petratos, R. Pitthan, R. Prepost, Y. Roblin, S. E. Rock, S. H. Rokni, G. Shapiro, T. Smith, P. A. Souder, M. Spengos, F. Staley, L. M. Stuart, Z. M. Szalata, Y. Terrien, A. K. Thompson, J. L. White, M. Woods, J. Xu, C. C. Young, G. Zapalac, E142 Collaboration

Physics Faculty Publications

The spin structure function of the neutron g₁ⁿ has been determined over the range 0.03 < x < 0.6 at an average Q² of 2 (GeV/c)² by measuring the asymmetry in deep inelastic scattering of polarized electrons from a polarized ³He target at energies between 19 and 26 GeV. The integral of the neutron spin structure function is found to be f-¹₀ gⁿ₁(x)dx = -0.022 ± 0.011. Earlier reported proton results together with the Bjorken sum rule predict f-¹₀ gⁿ₁(x)dx = -0.059 ± 0.019.

Fermi Surface And Magnetic Properties Of Low-Dimensional Organic Conductors, J. S. Brooks, S. J. Klepper, C. C. Agosta, M. Tokumoto, N. Kinoshita, Y. Tanaka, S. Uji, H. Aoki, A. S. Perel, G. J. Athas, X. Chen, D. A. Howe, H. Anzai

Physics

We report systematic high-magnetic-field and low-temperature measurements on several members of the α-(BEDT- TTF)2MHg(SCN)4 family of low-dimensional organic conductors. For M = K, transport, high-pressure and magnetic studies show the presence of a magnetic phase which is removed either with high magnetic fields or with high pressure. For M = Rb, transport measurements indicate the existence of a magnetic phase similar to the case for M = K, but with a higher transition temperature and critical field. For both M = K and Rb the split Landau level phenomenon is observed. We also report the pressure dependence of the Fermi …

Lamellar Ordering In Symmetric Diblock Copolymers, R. A. Sones, E. M. Terentjev, Rolfe G. Petschek

Faculty Scholarship

We calculate the lamellar period L and interphase thickness a of an incompressible melt of symmetric diblock copolymers from the onset of phase segregation (weak segregation limit) to the limit where segregation is almost complete (strong segregation limit) by numerically solving a mean field lattice model, where the lattice spacing is taken small enough to approximate a continuum. Our results for L and a agree with previously derived theoretical formulas in both limits. Based on the first few terms of a Fourier series expansion of the density profile, we show analytically that L = 0.844R(χN)0.571 at the weak segregation limit, …

²H (D,Γ) ⁴He Polarization Observables At 20, 30, And 50 Mev, R. M. Whitton, H. R. Weller, E. Hayward, W. R. Dodge, S. E. Kuhn

Physics Faculty Publications

Tensor and vector analyzing powers for the ²H (d,γ) ⁴He reaction have been obtained as a function of angle at E_d(lab) = 20, 30, and 50 MeV. Differential cross sections were extracted at 30 and 50 MeV. Data for A_yy(θ) and A_y(θ) were obtained at all three energies, while T₂₀(θ) was also measured at E_d(lab) = 50 MeV. A direct capture calculation was performed and compared to the data. This calculation assumes point deuterons and that the reaction proceeds primarily via E2 radiation in this energy region. A value of …

Resonant Vibrations Of The Irish Folk Harp, Patrick Healy

Other Resources

An analysis of the resonant vibration of an O’Meachair cedar and mahogany Irish folk harp is reported. A report is also made of a small number of measurements carried out on an O’Meachair spruce and maple Irish folk harp. The structure and operation of the harp is described.

The theory of small vibrations of plates and wooden boards is set out.

The system devised to measure input admittance at driving points on the harp body over a frequency range O-2 kHz is described. Tests of its linearity and out of its frequency flatness are reported.

Resonant vibrations of an isolated …

A Pulsed Power Design For The Linear Inductive Accelerator Modules For The Laboratory Microfusion Fa, Ronald E. Olson, D. L. Smith, M. G. Mazarakis, L. F. Bennett, T. R. Lockner

Physics Faculty Research & Creative Works

No abstract provided.

The Light Ion Lmf And Its Relevance To Ife, Ronald E. Olson, G. O. Allshouse, D. L. Cook, T. R. Lockner, M. G. Mazarakis, C. L. Olson, D. L. Smith

Physics Faculty Research & Creative Works

The inertial confinement fusion (ICF) program at Sandia National Laboratories (SNL) is directed toward validating light ions as an efficient driver for ICF defense and energy applications. The light ion laboratory microfusion facility (LMF) is envisioned as a facility in which high gain ICF targets could be developed and utilized in defense-related experiments. The relevance of LMF technology to eventual inertial fusion energy (IFE) applications is assessed via a comparison of LMF technologies with those projected in the Light Ion Beam Reactor Assessment (LIBRA) conceptual reactor design study

The Lmf Triaxial Mitl Voltage Adder System, Ronald E. Olson, M. G. Mazarakis, D. L. Smith, L. F. Bennett, T. R. Lockner, J. W. Poukey

Physics Faculty Research & Creative Works

No abstract provided.

Hysteresis And Anchoring Energy In Ferroelectric Liquid Crystals, Yuri Panarin

Articles

The frequency dispersion of the coercive force of Ferroelectric Liquid Crystals (FLC) cells has been detected and examined in the range of infralow (lower than 0.1 Hz) frequencies. To clarify the low-frequency dispersion, the model has been suggested, based on the arrangement of free charges and well describing the experimental curves. The method for determination of the energy of FLC anchoring at the surface, developed on the basis of the static hysteresis loop, has been proposed. The dependence of bistability and the anchoring energy upon the orientant layer thickness has experimentally been investigated.

Hydrodynamic Theory Of Multicomponent Diffusion And Thermal Diffusion In Multitemperature Gas Mixtures, John D. Ramshaw

Physics Faculty Publications and Presentations

A phenomenological theory is developed for multicomponent diffusion, including thermal diffusion, in gas mixtures in which the components may have different temperatures. The theory is based on the hydrodynamic approach of Maxwell and Stefan, as extended and elaborated by Furry [1] and Williams [2]. The present development further extends these earlier treatments to multiple temperatures and multicomponent thermal diffusion. The resulting diffusion fluxes obey generalized Stefan-Maxwell relations which include the effects of ordinary, forced, pressure, and thermal diffusion. When thermal diffusion is neglected, these relations have the same form as the usual single-temperature ones, except that mole fractions are replaced …

A Theoretical Model For Biased Superlattice Devices, Michael Ferner

Theses

A model describing the subband structures and tunneling characteristics of superlattices is presented. The model solves the envelope function equations by the transfer matrix technique. The results are codified in a Fortran program, and the model is applied to several structures.

Superlattice have been studied extensively, however many new structures await investigation.

This model is presented as a preliminary design tool. The program allows a designer to do preliminary calculations. This type of investigation guides a designer toward a goal by making possible a large number of calculations on many different structures.

Giant Suppression Of Flux-Flow Resistivity In Heavy-Ion Irradiated Tl2Ba2Ca2Cu3O10 Films: Influence Of Linear Defects On Vortex Transport, R.C. Budhani, M. Suenaga, Sy_Hwang Liou

Sy-Hwang Liou Publications

A large shift of the onset of flux-flow resistivity and the irreversibility line H_irr (T) to higher temperatures is observed in Tl₂Ba₂Ca₂Cu₃O₁₀ films containing linear defects created by Ag⁺²¹ ion irradiation. The H_irr(T), which has a characteristic ssL shape in highly anisotropic Tl and Bi based cuprates, becomes more like that of YBa₂Cu₃O₇ in the presence of these defects. The J_c at 77 K also shows a large increase as a result of flux localization at the …

Measurement Of Ionization And Phonon Production By Nuclear Recoils In A 60 G Crystal Of Germanium At 25 Mk, Tom Shutt, B. Ellman, P. D. Barnes Jr., Alan Cummings, Angela Da Silva, John Emes, Y. Giraud-Héraud, Eugene E. Haller, Andrew E. Lange, Ron R. Ross, J. Rich, Bernard Sadoulet, G. Smith, W. Stockwell, C. Stubbs, N. Wang, S. White, Betty A. Young, D. Yvon

Physics

We report on the first measurement of the absolute phonon energy and the amount of ionization produced by the recoil of nuclei and electrons in a 60 g germanium cyrstal at a temperature of ≊25 mK. We find good agreement between our results and previous measurements of ionization yield from nuclear recoils in germanium. Our device achieves 10:1 discrimination between neutrons and photons in the few keV energy range, demonstrating the feasibility of this technique for large reductions of background in searches for direct interactions of weakly interacting massive particle dark matter.