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2000

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Full-Text Articles in Physics

Unitarized Pseudoscalar Meson Scattering Amplitudes In Three Flavor Linear Sigma Models, Joseph Schechter, Deirdre Black, Amir H. Fariborz, Sherif Moussa, Salah Nasri Dec 2000

Unitarized Pseudoscalar Meson Scattering Amplitudes In Three Flavor Linear Sigma Models, Joseph Schechter, Deirdre Black, Amir H. Fariborz, Sherif Moussa, Salah Nasri

Physics

The three flavor linear sigma model is studied as a ``toy model'' for understanding the role of possible light scalar mesons in the \pi \pi, \pi K and \pi \eta scattering channels. The approach involves computing the tree level partial wave amplitude for each channel and unitarizing by a simple K-matrix prescription which does not introduce any new parameters. If the renormalizable version of the model is used there is only one free parameter. While this highly constrained version has the right general structure to explain \pi \pi scatteirng, it is ``not quite'' right. A reasonable fit can be made ...


Phase Diagram Of Three-Dimensional Dynamical Triangulations With A Boundary, Simon Catterall, Simeon Warner, Ray Renken Dec 2000

Phase Diagram Of Three-Dimensional Dynamical Triangulations With A Boundary, Simon Catterall, Simeon Warner, Ray Renken

Physics

We use Monte Carlo simulation to study the phase diagram of three-dimensional dynamical triangulations with a boundary. Three phases are indentified and characterized. One of these phases is a new, boundary dominated phase; a simple argument is presented to explain its existence. First-order transitions are shown to occur along the critical lines separating phases.


Higher Twist Contributions To R-Hadron Phenomenology In The Light Gluino Scenario, Thomas D. Gutierrez, R. Vogt, J. F. Gunion Dec 2000

Higher Twist Contributions To R-Hadron Phenomenology In The Light Gluino Scenario, Thomas D. Gutierrez, R. Vogt, J. F. Gunion

Physics

The open light gluino window allows non-trivial higher-twist gluino contributions to the proton wave function. Using a two-component model originally developed for charm hadroproduction, higher-twist intrinsic gluino contributions to final-state R-hadron formation are shown to enhance leading-twist production in the forward xnF region. We calculate R-hadron production at Pnlab=800 GeV in pp, pBe, and pCu interactions with light gluino masses of 1.2, 1.5, 3.5, and 5.0 GeV.


Chemical And Dynamical Speciation Of Mobile Ions In The Glassy Fast Ionic Conductor Ag2s+B2s3+Sis2: A 109ag Nuclear Magnetic Resonance Study, Tomoko Akai, Steve W. Martin, Ferdinando Borsa Dec 2000

Chemical And Dynamical Speciation Of Mobile Ions In The Glassy Fast Ionic Conductor Ag2s+B2s3+Sis2: A 109ag Nuclear Magnetic Resonance Study, Tomoko Akai, Steve W. Martin, Ferdinando Borsa

Materials Science and Engineering Publications

109Ag NMR in the highly conductive glass 0.525Ag2S+0.475(0.5B2S3+0.5SiS2) was investigated from 230 to 433 K. The 109Ag NMR spectra reveal for the first time three well resolved lines corresponding to three kinds of chemically speciated Ag ions in sites with different chemical shifts in a macroscopically homogeneous glass. This chemical speciation of Ag ions is discussed in relation to the microstructure of the glass. As the temperature is increased, the three lines that originate from three different species of ions are narrowed, but these lines exist independently up to 433 K, the highest ...


Electrons In Image States Near Roughened Metal Surfaces, Brian K. Clark, Brian W. Gregory, Jean M. Standard Dec 2000

Electrons In Image States Near Roughened Metal Surfaces, Brian K. Clark, Brian W. Gregory, Jean M. Standard

Faculty Publications – Chemistry

Electrons near roughened Ag and Au surfaces with chemisorbed dielectric overlayers of alkanethiol or alkaneselenol self-assembled monolayers are shown to move within the sulfur or selenium head-group layer on the metal terraces. The electrons exist in image states with respect to Ag or Au step edges. There is no substantial image force between the electrons and the terraces.


A Two-Chain Path Integral Model Of Positronium, L. Larrimore, R. N. Mcfarland, P. A. Sterne, Amy Lisa Graves Dec 2000

A Two-Chain Path Integral Model Of Positronium, L. Larrimore, R. N. Mcfarland, P. A. Sterne, Amy Lisa Graves

Physics & Astronomy Faculty Works

We have used a path integral Monte Carlo technique to simulate positronium (Ps) in a cavity. The primitive propagator is used, with a pair of interacting chains representing the positron and electron. We calculate the energy and radial distribution function for Ps enclosed in a hard, spherical cavity, and the polarizability of the model Ps in the presence of an electrostatic field. We find that the positron distribution near the hard wall differs significantly from that for a single particle in a hard cavity. This leads to systematic deviations from predictions of free-volume models which treat Ps as an effective ...


Master Equation For Hydrogen Recombination On Grain Surfaces, Gianfranco Vidali, Ofer Biham, Itay Furman, Valerio Pirronello Dec 2000

Master Equation For Hydrogen Recombination On Grain Surfaces, Gianfranco Vidali, Ofer Biham, Itay Furman, Valerio Pirronello

Physics

Recent experimental results on the formation of molecular hydrogen on astrophysically relevant surfaces under conditions similar to those encountered in the interstellar medium provided useful quantitative information about these processes. Rate equation analysis of experiments on olivine and amorphous carbon surfaces provided the activation energy barriers for the diffusion and desorption processes relevant to hydrogen recombination on these surfaces. However, the suitability of rate equations for the simulation of hydrogen recombination on interstellar grains, where there might be very few atoms on a grain at any given time, has been questioned. To resolve this problem, we introduce a master equation ...


Cross Section For B-Jet Production In P̅P Collisions At √S = 1.8 Tev, B. Abbott, Gregory R. Snow, D0 Collaboration Dec 2000

Cross Section For B-Jet Production In P̅P Collisions At √S = 1.8 Tev, B. Abbott, Gregory R. Snow, D0 Collaboration

Gregory Snow Publications

Bottom-quark production in p̅p collisions at √s = 1.8 TeV is studied with 5 pb-1 of data collected in 1995 by the D0 detector at the Fermilab Tevatron Collider. The differential production cross section for b jets in the central rapidity region (∣yb∣< 1) as a function of jet transverse energy is extracted from a muon-tagged jet sample. Within experimental and theoretical uncertainties, D0 results are found to be higher than, but compatible with, next-to-leading-order QCD predictions.


Phase-Coherent Multilevel Two-Photon Transitions In Cold Rb Atoms: Ultrahigh-Resolution Spectroscopy Via Frequency-Stabilized Femtosecond Laser, Tai Hyun Yoon, Adela Marian, John L. Hall, Jun Ye Dec 2000

Phase-Coherent Multilevel Two-Photon Transitions In Cold Rb Atoms: Ultrahigh-Resolution Spectroscopy Via Frequency-Stabilized Femtosecond Laser, Tai Hyun Yoon, Adela Marian, John L. Hall, Jun Ye

Physics Faculty Contributions

A two-photon transition in cold Rb atoms will be probed with a phase-coherent wide bandwidth femtosecond laser comb. Frequency domain analysis yields a high-resolution picture where phase coherence among various transition pathways through different intermediate states produces interference effects on the resonantly enhanced transition probability. This result is supported by the time domain Ramsey interference effect. The two-photon transition spectrum is analyzed in terms of the pulse repetition rate and carrier frequency offset, leading to a cold-atom-based frequency stabilization scheme for both degrees of freedom of the femtosecond laser.


Low-Frequency Crossover Of The Fractional Power-Law Conductivity In Srruo3, J. S. Dodge, Christopher P. Weber, J. Corson, J. Orenstein, Z. Schlesinger, J. W. Reiner, M. R. Beasley Dec 2000

Low-Frequency Crossover Of The Fractional Power-Law Conductivity In Srruo3, J. S. Dodge, Christopher P. Weber, J. Corson, J. Orenstein, Z. Schlesinger, J. W. Reiner, M. R. Beasley

Physics

We combine the results of terahertz time-domain spectroscopy with far-infrared transmission and reflectivity to obtain the conductivity of SrRuO 3 over an unprecedented continuous range in frequency, allowing us to characterize the approach to zero frequency as a function of temperature. We show that the conductivity follows a simple phenomenological form, with an analytic structure fundamentally different from that predicted by the standard theory of metals.


Ga-Doped Zno Films Grown On Gan Templates By Plasma-Assisted Molecular-Beam Epitaxy, H. J. Ko, Yanfang Chen, S. K. Hong, H. Wenisch, T. Yao, David C. Look Dec 2000

Ga-Doped Zno Films Grown On Gan Templates By Plasma-Assisted Molecular-Beam Epitaxy, H. J. Ko, Yanfang Chen, S. K. Hong, H. Wenisch, T. Yao, David C. Look

Physics Faculty Publications

We have investigated the structural and optical properties of Ga-doped ZnO films grown on GaN templates by plasma-assisted molecular-beam epitaxy. The carrier concentration in Ga-doped ZnO films can be controlled from 1.33×1018/cm3 to 1.13×1020/cm3. Despite high Ga incorporation, the linewidth of (0002) ω-rocking curves of Ga-doped ZnO films still lies in the range from 5 to 15 arc min. Photoluminescence (PL) spectra of Ga-doped ZnO films show dominant near-bandedge emission with negligibly weak deep-level emission, independent of carrier concentration. The PL spectrum exhibits a new emission line at 3.358 ...


Measurement Of The W Boson Mass Using Large Rapidity Electrons, B. Abbott, Gregory R. Snow, D0 Collaboration Dec 2000

Measurement Of The W Boson Mass Using Large Rapidity Electrons, B. Abbott, Gregory R. Snow, D0 Collaboration

Gregory Snow Publications

We present a measurement of the W boson mass using data collected by the DØ. experiment at the Fermilab Tevatron during 1994–1995. We identify W bosons by their decays to en final states where the electron is detected in a forward calorimeter. We extract the W boson mass MW by fitting the transverse mass and transverse electron and neutrino momentum spectra from a sample of 11 089 Weν decay candidates. We use a sample of 1687 dielectron events, mostly due toZee decays, to constrain our model of the detector response. Using the forward calorimeter ...


On The Persistence Of Small Regions Of Vorticity In The Protoplanetary Nebula, S. S. Davis, D. P. Sheehan, J. N. Cuzzi Dec 2000

On The Persistence Of Small Regions Of Vorticity In The Protoplanetary Nebula, S. S. Davis, D. P. Sheehan, J. N. Cuzzi

Physics and Biophysics: Faculty Scholarship

The fate of small regions of vorticity in a barotropic model of the protoplanetary nebula is investigated over thousands of years using a finite difference model. It is found that the coherence time for a small island of vorticity depends on its size, strength, orientation, and radial location in the nebula. Anticyclonic vorticity retains its coherence for longer times than cyclonic vorticity due to favorable interactions with the Keplerian shear flow. Rossby waves are generated as a result of mean vorticity gradients across the disk. The two-dimensional nebula evolves from discrete vortices into an axisymmetric flow consisting of small-amplitude vortex ...


Optical And Magneto-Optical Properties And Electronic Structures Of Single-Crystalline Ral2 (R=Y, La, Ce, Pr, And Lu), R. J. Lange, S. J. Lee, K. J. Kim, Paul C. Canfield, David W. Lynch Dec 2000

Optical And Magneto-Optical Properties And Electronic Structures Of Single-Crystalline Ral2 (R=Y, La, Ce, Pr, And Lu), R. J. Lange, S. J. Lee, K. J. Kim, Paul C. Canfield, David W. Lynch

Physics and Astronomy Publications

The diagonal optical conductivity spectra of single crystals of RAl2 (R=Y, La, Ce, Pr, and Lu) were measured at room temperature by spectroscopic ellipsometry in the 1.5–5.6−eV range. All the compounds exhibit two strong interband absorption peaks at about 1.8 and 3.6 eV for YAl2 and LuAl2, and at about 2.0 and 3.0 eV for LaAl2, CeAl2, and PrAl2. Such differences in the second peak position appear in the theoretical optical conductivity spectra calculated from their band structures obtained by the tight-binding linear-muffin-tin-orbitals method. Most of the contributions to the two ...


Stabilization Of Bound State Decay In An Intense Monochromatic High-Frequency Field, N. L. Manakov, M. V. Frolov, Bogdan Borca, Anthony F. Starace Dec 2000

Stabilization Of Bound State Decay In An Intense Monochromatic High-Frequency Field, N. L. Manakov, M. V. Frolov, Bogdan Borca, Anthony F. Starace

Anthony F. Starace Publications

The formalism of complex quasienergies is used for exact calculation of the field-dependent decay rate for a weakly bound particle (in the model of a three-dimensional zero-range potential) in a strong monochromatic laser field. It is shown that the adiabatic (quasistationary) stabilization regime in this model occurs at frequencies ω exceeding the binding energy and only in a limited intensity range. A simple estimate is obtained for the critical field of stabilization breakdown. The effect may be observed for the decay of H ions in the field of a neodymium laser of femtosecond duration.


Surface Diffusion In Mixed Overlayers With Superlattice Ordering: Percolative Transport Around Obstacles And Along Domain Boundaries, Da-Jiang Liu, James W. Evans Dec 2000

Surface Diffusion In Mixed Overlayers With Superlattice Ordering: Percolative Transport Around Obstacles And Along Domain Boundaries, Da-Jiang Liu, James W. Evans

Mathematics Publications

To elucidate surface diffusion in the presence of a coadsorbate with superlattice ordering, we consider particle hopping on a square lattice with some fraction, u B , of quenched blocking sites arranged with checkerboard or c(232) ordering. Behavior for low u B corresponds to diffusion around isolated obstacles, and can be described by exact density expansions. Behavior for high u B corresponds to percolative diffusion along ~or sometimes away from! domain boundaries. The connectivity of these domain boundaries is closely related to the existence of symmetry breaking @i.e., long-range c(232) order# in the distribution of blocking sites. In ...


Electronic Structure Of Quasicrystalline Surfaces: Effects Of Surface Preparation And Bulk Structure, V. Fournée, P. J. Pinhero, J. W. Anderegg, Thomas A. Lograsso, A. R. Ross, Paul C. Canfield, I. R. Fisher, Patricia A. Thiel Dec 2000

Electronic Structure Of Quasicrystalline Surfaces: Effects Of Surface Preparation And Bulk Structure, V. Fournée, P. J. Pinhero, J. W. Anderegg, Thomas A. Lograsso, A. R. Ross, Paul C. Canfield, I. R. Fisher, Patricia A. Thiel

Chemistry Publications

We elucidate the nature of the surface electronic properties of quasicrystalline Al-Pd-Mn. We do this by using photoelectron and Auger electron spectroscopies, and by making a variety of comparisons—across types of bulk samples, and across methods of surface preparation. The main conclusions are these: (i) The narrow Mn 2p3/2core-level line observed in the icosahedral phase is a fingerprint of a suppression in the density of states (a pseudogap) at the Fermi level and is not unique to the quasicrystalline phase. It is also independent of the symmetry of the quasicrystalline surface. The Auger line shape is ...


Surface Segregation And Restructuring Of Colossal-Magnetoresistant Manganese Perovskites La0.65Sr0.35Mno3, Hani Dulli, Peter A. Dowben, Sy-Hwang Liou, E. Ward Plummer Dec 2000

Surface Segregation And Restructuring Of Colossal-Magnetoresistant Manganese Perovskites La0.65Sr0.35Mno3, Hani Dulli, Peter A. Dowben, Sy-Hwang Liou, E. Ward Plummer

Faculty Publications, Department of Physics and Astronomy

We have investigated the surface chemical composition of crystalline films of La0.65Sr0.35MnO3 by angle-resolved x-ray photoelectron spectroscopy. The surface composition was found to be significantly different from that of the bulk because of an appreciable Sr segregation. Furthermore, our study suggests that this Sr segregation has caused a major restructuring of the surface region characterized by the formation of a Ruddlesden-Popper phase (La,Sr)n+1MnnO3n+1 with n = 1. Segregation and restructuring in the surface region should be common in these doped perovskites and will have a profound ...


Dynamics Of Signaling Between Ca(2+) Sparks And Ca(2+)- Activated K(+) Channels Studied With A Novel Image-Based Method For Direct Intracellular Measurement Of Ryanodine Receptor Ca(2+) Current, Ronghua Zhuge, Kevin E. Fogarty, Richard A. Tuft, Lawrence M. Lifshitz, Kemal Sayar, John V. Walsh Dec 2000

Dynamics Of Signaling Between Ca(2+) Sparks And Ca(2+)- Activated K(+) Channels Studied With A Novel Image-Based Method For Direct Intracellular Measurement Of Ryanodine Receptor Ca(2+) Current, Ronghua Zhuge, Kevin E. Fogarty, Richard A. Tuft, Lawrence M. Lifshitz, Kemal Sayar, John V. Walsh

Open Access Articles

Ca(2+) sparks are highly localized cytosolic Ca(2+) transients caused by a release of Ca(2+) from the sarcoplasmic reticulum via ryanodine receptors (RyRs); they are the elementary events underlying global changes in Ca(2+) in skeletal and cardiac muscle. In smooth muscle and some neurons, Ca(2+) sparks activate large conductance Ca(2+)-activated K(+) channels (BK channels) in the spark microdomain, causing spontaneous transient outward currents (STOCs) that regulate membrane potential and, hence, voltage-gated channels. Using the fluorescent Ca(2+) indicator fluo-3 and a high speed widefield digital imaging system, it was possible to capture the total ...


Measurement Of The Decay Amplitudes Of B0JK*0 And BS0J/Ψφ Decays, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Nov 2000

Measurement Of The Decay Amplitudes Of B0 → J/ΨK*0 And BS0 → J/Ψφ Decays, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

An angular analysis of B0JK*0and Bs0J/ψφ has been used to determine the decay amplitudes with parity-even longitudinal (A0) and transverse (A) polarization and parity-odd transverse (A) polarization. The measurements are based on 190 B0 and 40Bs0candidates obtained from 89 pb-1 of p̅p collisions at the Fermilab Tevatron. The longitudinal decay amplitude dominates with |A0|2= 0.59 ± 0.06 ± 0.01 for B0 and |A0|2 = 0.61 ± 0.14 ± 0.02 for Bs0 decays. The parity-odd ...


The Hall A Aerogel Čerenkov Detector, Marius Coman Nov 2000

The Hall A Aerogel Čerenkov Detector, Marius Coman

FIU Electronic Theses and Dissertations

The efficiency of the Aerogel Čerenkov detector for detecting particles having velocities greater than the speed of light in the aerogel media and the yield for rejecting particles having subthreshold velocities - smaller than the speed of light in the interaction media - was studied and is presented. The efficiency/inefficiency determination of the Aerogel Čerenkov detector consists of calculating the probabilities that a particle having a velocity above/below threshold generates a photoelectron in the aerogel block. The efficiency is determined using the normalised pulse height distribution of the photoelectrons. The Aerogel Čerenkov detector will play a key role in particle ...


The Dissociative Recombination Of The Helium Molecular Ion The Observed Final Products, Luminita Coman Nov 2000

The Dissociative Recombination Of The Helium Molecular Ion The Observed Final Products, Luminita Coman

FIU Electronic Theses and Dissertations

Dissociative recombination reaction has been studied theoretically and experimentally for about four decades. Because of the complexity of this process there is not yet a definite agreement between theory and experiment. In this work, dissociative recombination (DR) of helium molecular ion in thermal plasma was studied using Time of Flight (TOF) spectroscopy. This method allowed the identification of the final atom states products of DR. We found the following final products of the DR of the molecular ion: He(3S; 1s3s), He(1S; 1s3s), He(3P; 1s3p), He(3D; 1s3d), He(1D; 1s3d), He(1 ...


Precision Phase Control Of An Ultrawide-Bandwidth Femtosecond Laser: A Network Of Ultrastable Frequency Marks Across The Visible Spectrum, Jun Ye, John L. Hall, Scott A. Diddams Nov 2000

Precision Phase Control Of An Ultrawide-Bandwidth Femtosecond Laser: A Network Of Ultrastable Frequency Marks Across The Visible Spectrum, Jun Ye, John L. Hall, Scott A. Diddams

Physics Faculty Contributions

We demonstrate that the stability of the current optical frequency comb generated by a Kerr-lens mode-locked femtosecond laser is limited by the microwave reference used for phase locking the comb spacing. Hence we implement precision frequency/phase control of the entire comb to the fundamental and second-harmonic frequencies of a stable cw laser without any external microwave reference. The stability of a cw iodine-stabilized laser is transferred to millions of comb lines (with an instability of 3×10−13) covering more than one octave of the optical frequency spectrum. In addition, the mode spacing of the comb can be used ...


A Discotic Disguised As A Smectic: A Hybrid Columnar Bragg Glass, Karl Saunders, Leo Radzihovsky, John Toner Nov 2000

A Discotic Disguised As A Smectic: A Hybrid Columnar Bragg Glass, Karl Saunders, Leo Radzihovsky, John Toner

Physics

We show that discotics, lying deep in the columnar phase, can exhibit an x-ray scattering pattern which mimics that of a somewhat unusual smectic liquid crystal. This exotic, new glassy phase of columnar liquid crystals, which we call a “hybrid columnar Bragg glass,” can be achieved by confining a columnar liquid crystal in an anisotropic random environment of, e.g., strained aerogel. Long-ranged orientational order in this phase makes single-domain x-ray scattering possible, from which a wealth of information could be extracted. We give detailed quantitative predictions for the scattering pattern in addition to exponents characterizing anomalous elasticity of the ...


Photonuclear Physics: Laser Splits Atom, Donald Umstadter Nov 2000

Photonuclear Physics: Laser Splits Atom, Donald Umstadter

Donald Umstadter Publications

Lasers have become ubiquitous, being used in everything from a bar-code reader to a compact disk player. Who would have thought that they might be used to split the atom? A few scientists proposed to do just that more that a decade ago. But accomplishing it in the laboratory had to await the maturity of new technology, which enabled the construction of the world's most powerful lasers at the Lawrence Livermore National Laboratory in the United States and at the Rutherford Appleton Laboratory in the United Kingdom. Now two independent research teams have used these lasers to split the ...


From Avalanches To Fluid Flow: A Continuous Picture Of Grain Dynamics Down A Heap, P. A. Lemieux, Douglas J. Durian Nov 2000

From Avalanches To Fluid Flow: A Continuous Picture Of Grain Dynamics Down A Heap, P. A. Lemieux, Douglas J. Durian

Department of Physics Papers

Surface flows are excited by steadily adding spherical glass beads to the top of a heap. To simultaneously characterize the fast single-grain dynamics and the much slower collective intermittency of the flow, we extend photon-correlation spectroscopy via fourth-order temporal correlations in the scattered light intensity. We find that microscopic grain dynamics during an avalanche are similar to those in the continuous flow just above the transition. We also find that there is a minimum jamming time, even arbitrarily close to the transition.


Dijet Production By Double Pomeron Exchange At The Fermilab Tevatron, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Nov 2000

Dijet Production By Double Pomeron Exchange At The Fermilab Tevatron, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We report the first observation of dijet events with a double Pomeron exchange topology produced in p̅p collisions at √s= 1800 GeV. The events are characterized by a leading antiproton, two jets in the central pseudorapidity region, and a large rapidity gap on the outgoing proton side. We present results on jet kinematics and production rates, compare them with corresponding results from single diffractive and inclusive dijet production, and test factorization.


Continuum Pumping Of [Fe Ii] In The Orion Nebula, E. M. Verner, D. A. Verner, J. A. Baldwin, Gary J. Ferland, P. G. Martin Nov 2000

Continuum Pumping Of [Fe Ii] In The Orion Nebula, E. M. Verner, D. A. Verner, J. A. Baldwin, Gary J. Ferland, P. G. Martin

Physics and Astronomy Faculty Publications

This paper presents detailed comparisons between numerical simulations of Fe II emission spectra and recent high-resolution and signal-to-noise spectra of the Orion Nebula. We have identified 40 [Fe II] lines in the spectrum, allowing extensive comparisons between theory and observations. The identifications are based on predictions of a realistic model of the Fe II atom, which includes the lowest 371 levels (all levels up to 11.6 eV). We investigate the dependence of the spectrum on electron density and on pumping by the stellar continuum. Orion is important because it provides a relatively simple environment in which to test complex ...


Control Of Intense Laser- Atom Processes With Strong Static Fields, Dejan B. Milosevic, Anthony F. Starace Nov 2000

Control Of Intense Laser- Atom Processes With Strong Static Fields, Dejan B. Milosevic, Anthony F. Starace

Anthony F. Starace Publications

Atomic processes in the presence of intense fields continue to attract a great deal of attention [1-3]. Key goals of research in this area are to increase the intensities and frequencies of coherent light produced in these processes. In two recent works [4,5] we have demonstrated theoretically the possibility of controlling intense laser-atom interaction processes by employing strong, but experimentally feasible, static electric or magnetic fields. Thus, in Ref. [4] we demonstrated how a strong static electric field may induce a high-energy plateau for scattered x-ray photons in laser-assisted, x-ray-atom scattering in which the incident x-rays were assumed to ...


Analytic Environment-Dependent Tight-Binding Bond Integrals: Application To Mosi2, Duc Nguyen-Manh, David G. Pettifor, Vaclav Vitek Nov 2000

Analytic Environment-Dependent Tight-Binding Bond Integrals: Application To Mosi2, Duc Nguyen-Manh, David G. Pettifor, Vaclav Vitek

Departmental Papers (MSE)

We present the first derivation of explicit analytic expressions for the environmental dependence of the σ, π, and δ bond integrals within the orthogonal two-center tight-binding approximation by using the recently developed bond-order potential theory to invert the nonorthogonality matrix. We illustrate the power of this new formalism by showing that it not only captures the transferability of the bond integrals between elemental bcc Mo and Si and binary C11b MoSi2 but also predicts the absence of any discontinuity between first and second nearest neighbors for the ddσ bond integral even though large discontinuities exist for ppσ ...