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Series

1993

Faculty Publications

Articles 1 - 14 of 14

Full-Text Articles in Physics

Neutron Reflection Interferometry: Physical Principles Of Surface Analysis With Phase Information, Vladimir Gudkov, G. I. Opat, A. G. Klein Dec 1993

Neutron Reflection Interferometry: Physical Principles Of Surface Analysis With Phase Information, Vladimir Gudkov, G. I. Opat, A. G. Klein

Faculty Publications

It is shown that the analysis of surface layers by neutron reflection interferometry is considerably enhanced by performing the reflectometry with phase information. We discuss two methods of providing such information. One method involves physically adding an extra reference layer, whose amplitude and phase are known theoretically. The other uses the Lloyd's mirror configuration, in which a directly propagating ray that interferes with the reflected ray supplies the phase information. The methods have much in common with holography.

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Driven Diffusion Of Particles, First-Passage Front, And Interface Growth, R. Bidaux, Ras B. Pandey Oct 1993

Driven Diffusion Of Particles, First-Passage Front, And Interface Growth, R. Bidaux, Ras B. Pandey

Faculty Publications

We study a computer-simulation model for driven particles on a discrete lattice where a fraction p of the lattice sites is randomly occupied by frozen impurities (barriers), and an imposed bias governs the particles’ hopping through the lattice. These particles (the carriers) are initially released from a source of wetting fluid from one end of the lattice in order to wet and the dry lattice on their trails. We study the transport of particles, frontier of their trail, and the growth of the interface between the wet and dry regions as a function of the biased field and the number …

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Driven Diffusion, Kawasaki Dynamics, Mixing, And Spatial Ordering In An Interacting Lattice-Gas, Yan He, Ras B. Pandey Jul 1993

Driven Diffusion, Kawasaki Dynamics, Mixing, And Spatial Ordering In An Interacting Lattice-Gas, Yan He, Ras B. Pandey

Faculty Publications

Kawasaki dynamics is used to study the transport properties of a nonequilibrium steady state system of interacting lattice gas of oppositely charged particles in a linear gradient field in two dimensions. The rms displacements show unusual nondiffusive transport. The effective conductivity varies with the temperature which deviates from the Arrhenius law and depends on the range of interaction. Density of a fully mixed state decays with temperature with a power law. Onset of spatial ordering occurs in a certain temperature range at a fixed range of interaction.

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Low‐Cost Technique For Preparing N‐Sb2S3/P‐Si Heterojunction Solar Cells, O. Savadogo, K. C. Mandal Jul 1993

Low‐Cost Technique For Preparing N‐Sb2S3/P‐Si Heterojunction Solar Cells, O. Savadogo, K. C. Mandal

Faculty Publications

No abstract provided.

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Ordering Processes In Porous-Media, J.C. Lee Jun 1993

Ordering Processes In Porous-Media, J.C. Lee

Faculty Publications

The ordering processes in a binary liquid mixture confined in a Vycor type of pore and at temperatures near the transition temperature of the pure system Tc are studied using a kinetic Ising model and the method of Monte Carlo simulations. The results for dynamics show quite clear signatures of the pore width but no notable difference between T > Tc and T < Tc. In the results for statics, the small angle part of the structure factor increases rapidly as T approaches Tc in the one-phase region. This suggests the onset of ordering but the fluctuation of …

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Large Amplitude L=1 Coherent Structures In Non-Neutral Plasmas Confined In A Cylindrical Trap, Ross L. Spencer, Grant W. Mason Jun 1993

Large Amplitude L=1 Coherent Structures In Non-Neutral Plasmas Confined In A Cylindrical Trap, Ross L. Spencer, Grant W. Mason

Faculty Publications

The computation of l= 1 coherent structures in non-neutral plasmas with arbitrary density profiles and for large displacements of the plasma from the symmetry axis of a confining cylindrical trap is described. As the structures are displaced from the axis, they revolve about the symmetry axis with a frequency that typically increases with displacement. The plasma also is distorted into an approximately elliptical shape. The frequency shifts and the eccentricities as a function of displacement, plasma size, and the shape of the density profile are both computed numerically and calculated analytically. The results are shown to be consistent with data …

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Photoluminescence And Absorption Studies Of Defects In Cdte And Znxcd1-Xte Crystals, Cheryl Barnett Davis, David D. Allred, A. Reyes-Mena, Jesus González-Hernández, Ovidio González, Bret C. Hess, Worth P. Allred May 1993

Photoluminescence And Absorption Studies Of Defects In Cdte And Znxcd1-Xte Crystals, Cheryl Barnett Davis, David D. Allred, A. Reyes-Mena, Jesus González-Hernández, Ovidio González, Bret C. Hess, Worth P. Allred

Faculty Publications

We have studied at cryogenic temperatures photoluminescence features which lie more than 0.15 eV below the band edge in ZnxCd1-xTe (0≤x≤0.09) crystals. The same features, namely a defect band which lies at about 0.13-0.20 eV below the band-gap energy and a peak at 1.1 eV, that are observed in pure CdTe samples are observed in these alloy materials. In annealed samples we observe that the 1.1 eV feature, which has been attributed to tellurium vacancies, increases with fast cooling. Increased concentrations of tellurium vacancies can be understood in terms of the phase diagram of CdTe which indicates that higher concentrations …

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Evidence Of A Nondiffusive Transport In A Monodisperse Screened Coulomb System By A Molecular-Dynamics Simulation, Michael Wild, Ras B. Pandey May 1993

Evidence Of A Nondiffusive Transport In A Monodisperse Screened Coulomb System By A Molecular-Dynamics Simulation, Michael Wild, Ras B. Pandey

Faculty Publications

A molecular-dynamics simulation is carried out for particles (tracers) interacting with a screened Coulomb potential in three dimensions. A phase transition is observed from a liquid to an fcc solid on reducing the temperature at a fixed density, consistent with previous studies. In the liquid phase, the variation of the rms displacement Rtr of the charged particles with time seems to depend on the density and the temperature. In the short-time regime, the effective exponent k for the subdiffusive power-law behavior, i.e., Rtr∼tk, decreases on increasing the density and lowering the temperature. A crossover from …

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Cp-Odd Nucleon Potential, Vladimir Gudkov, Xiao-Gang He, Bruce H.J. Mckellar May 1993

Cp-Odd Nucleon Potential, Vladimir Gudkov, Xiao-Gang He, Bruce H.J. Mckellar

Faculty Publications

The P-odd and CP-odd nucleon potential for different models of CP violation in the one-meson exchange approximation is studied. It is shown that the main contribution is due to the π-meson exhcange which leads to a simple one-parameter CP-odd nucleon potential.

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Low-Frequency Feature In The First-Order Raman Spectrum Of Amorphous Carbon, David D. Allred, Qi Wang, Jesus González-Hernández Mar 1993

Low-Frequency Feature In The First-Order Raman Spectrum Of Amorphous Carbon, David D. Allred, Qi Wang, Jesus González-Hernández

Faculty Publications

In the first-order Raman spectrum of amorphous carbon (a-C) there is a low-frequency feature in the 200-900-cm-1 region. This feature is characteristic of the highly disordered amorphous-carbon materials. We note that the intensity of this feature is very sensitive to the thermal history of samples, thus suggesting that it is an important measure of the degree of disorder of the a-C materials. We also discuss the relationship between this feature and the phonon density of states of graphite.

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Exponential Growth Of An Unstable L=1 Diocotron Mode For A Hollow Electron Column In A Warm-Fluid Model, S. Neil Rasband, Ross L. Spencer, Richard R. Vanfleet Mar 1993

Exponential Growth Of An Unstable L=1 Diocotron Mode For A Hollow Electron Column In A Warm-Fluid Model, S. Neil Rasband, Ross L. Spencer, Richard R. Vanfleet

Faculty Publications

Numerical investigations of a warm-fluid model with an isothermal equation of state for the perpendicular dynamics of an axisymmetric, magnetically confined pure electron plasma predict an exponentially unstable, l=1, diocotron mode for hollow density profiles. The unstable mode can be identified with a stable, nonsmooth mode that exists in cold drift models but which is destabilized by finite temperature effects. The unstable mode has many properties similar to the experimental results reported by Driscoll [Phys. Rev. Lett. 64, 645 (1990)].

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In-Medium Behavior Of The Qcd ϴ Term And The Value Of Cp Violation In Nuclei, Vladimir Gudkov Feb 1993

In-Medium Behavior Of The Qcd ϴ Term And The Value Of Cp Violation In Nuclei, Vladimir Gudkov

Faculty Publications

The expectation value of the θ term in QCD for nuclear matter is estimated in the nucleon gas approximation. There is no significant renormalization (to an accuracy ∼10%) of the CP violation in nuclei due to the similar behaviors for the in-medium values of the θ term and quark condensates.

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Quantam Wave Turbulence, Alejandro Garcia, M. Haeri, S. Putterman, P. Roberts Jan 1993

Quantam Wave Turbulence, Alejandro Garcia, M. Haeri, S. Putterman, P. Roberts

Faculty Publications

The nonlinear quantum kinetic equation for the interaction of sound waves is solved via analytic and numerical techniques. In the classical regime energy cascades to higher frequency (ω) according to the steady-state power law ω-3/2. In the quantum limit, the system prefers a reverse cascade of energy which follows the power law ω-6. Above a critical flux, a new type of spectrum appears which is neither self-similar nor close to equilibrium. This state of nonlinear quantum wave turbulence represents a flow of energy directly from the classical source to the quantum degrees of freedom.

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Sign Correlations And The Mechanism For Parity Violation, Vladimir Gudkov Jan 1993

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.

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