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Physics Faculty Research & Creative Works

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Articles 1111 - 1140 of 1762

Full-Text Articles in Physical Sciences and Mathematics

Non-Sequential Double Ionization Of Ne In Intense Laser Pulses: A Coincidence Experiment, Robert Moshammer, Bernold Feuerstein, Daniel Fischer, Alexander Dorn, Claus Dieter Schroter, J. Deipenwisch, Jose R. Crespo Lopez-Urrutia, C. Hohr, Paul B. Neumayer, Joachim Hermann Ullrich, Horst Rottke, Christoph Trump, M. Wittmann, Georg Korn, Wolfgang Sandner Mar 2001

Non-Sequential Double Ionization Of Ne In Intense Laser Pulses: A Coincidence Experiment, Robert Moshammer, Bernold Feuerstein, Daniel Fischer, Alexander Dorn, Claus Dieter Schroter, J. Deipenwisch, Jose R. Crespo Lopez-Urrutia, C. Hohr, Paul B. Neumayer, Joachim Hermann Ullrich, Horst Rottke, Christoph Trump, M. Wittmann, Georg Korn, Wolfgang Sandner

Physics Faculty Research & Creative Works

The dynamics of Neon double ionization by 25 fs, 1.0 PW/cm2 laser pulses at 795 nm has been studied in a many particle coincidence experiment. The momentum vectors of all ejected atomic fragments (electrons and ions) have been measured using combined electron and recoil-ion momentum spectroscopy. Electron emission spectra for double and single ionization will be discussed. In both processes the mean electron energies differ considerably and high energetic electrons with energies of more than 120 eV have been observed for double ionization. The experimental results are in qualitative agreement with the rescattering model.

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Fully Differential Cusp Electron Production Cross Sections For 75-Kev H₂⁺ + He Collisions, L. An, Kh Khayvat, Michael Schulz Feb 2001

Fully Differential Cusp Electron Production Cross Sections For 75-Kev H₂⁺ + He Collisions, L. An, Kh Khayvat, Michael Schulz

Physics Faculty Research & Creative Works

A kinematically complete experiment on single ionization for 75-keV H2+ + H e collisions was performed by measuring the fully momentum analyzed projectiles and recoil ions in coincidence. The electron momentum was deduced from momentum conservation. Clear signatures of the postcollision interaction between the outgoing projectiles and the electrons were observed in the momentum spectra of all collision products simultaneously.

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Two-Dimensional Black Holes As Open Strings: A New Realization Of The Ads/Cft Correspondence, Mariano Cadoni, Marco Cavaglia Feb 2001

Two-Dimensional Black Holes As Open Strings: A New Realization Of The Ads/Cft Correspondence, Mariano Cadoni, Marco Cavaglia

Physics Faculty Research & Creative Works

We show that weak-coupled two-dimensional dilation gravity on anti-de Sitter space can be described by the dynamics of an open string. Neumann and Dirichlet boundary conditions for the string lead two different realizations of the anti-de Sitter/Conformal Field Theory correspondence. In particular, in the Dirichlet case the thermodynamical entropy of two-dimensional black holes can be exactly reproduced by counting the string states.

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Electric Field Controlled, Pulsed Autoionization In Two Electron Wave Packets, J. Greg Story, Heider N. Ereifej Jan 2001

Electric Field Controlled, Pulsed Autoionization In Two Electron Wave Packets, J. Greg Story, Heider N. Ereifej

Physics Faculty Research & Creative Works

In this paper, control of the evolution of a two electron wave packet through the application of a static electric field is demonstrated. Specifically, application of a small electric field is used to produce pulsed autoionization events, the timing of which can be controlled on a picosecond time scale. The technique is demonstrated by exciting calcium atoms using a short-pulsed laser to the 4p3/219d doubly excited state, which is energy degenerate with the 4p1/2nk stark states. Evolution of the resultant wave packet is monitored through the application of a second short laser pulse, which stimulates the …

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Structural, Electronic, And Magnetic Properties Of Lani₅₋ₓtₓ (T = Fe, Mn) Compounds, Jinbo Yang, Chiu-Ying Tai, G. K. Marasinghe, George Daniel Waddill, Oran Allan Pringle, William Joseph James, Y. Kong Jan 2001

Structural, Electronic, And Magnetic Properties Of Lani₅₋ₓtₓ (T = Fe, Mn) Compounds, Jinbo Yang, Chiu-Ying Tai, G. K. Marasinghe, George Daniel Waddill, Oran Allan Pringle, William Joseph James, Y. Kong

Physics Faculty Research & Creative Works

Structures and magnetic properties of the LaNi5-xFex and LaNi5-xMnx compounds have been investigated using neutron diffraction and first-principles tight-binding-linear-muffin-tin-orbital methods. Both neutron diffraction refinement data and total energy calculations show that the Fe and Mn atoms preferentially occupy the 3g sites in the hexagonal CaCu5-type structure. The calculated magnetic moments of Fe and Ni atoms are of 2.4-2.5μB and 0.2-0.5μB in LaNi5-xFex, respectively. The magnetic structure exhibits more localized moments at Fe atoms in LaNi5-xFex when x ≤ 1.0. Electronic structure calculations indicate …

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Magnetization And Heat Capacity Of R1/3sr2/3feo3-Δ (R = La And Pr), V. P.S. Awana, M. Karppinen, H. Yamauchi, S. K. Malik, William B. Yelon, Apurva Mehta, A. V. Narlikar Jan 2001

Magnetization And Heat Capacity Of R1/3sr2/3feo3-Δ (R = La And Pr), V. P.S. Awana, M. Karppinen, H. Yamauchi, S. K. Malik, William B. Yelon, Apurva Mehta, A. V. Narlikar

Physics Faculty Research & Creative Works

Results of magnetization and heat capacity (CP) measurements are presented for R1/3Sr2/3FeO3-δ compounds with R = La and Pr. The change in entropy (ΔS) near the magnetic transition amounts to only 15% of the theoretically expected value for the Fe3+ or Fe5+ spins magnetic ordering. The lower value of ΔS is explained on the basis of reported Mössbauer studies, which revealed a substantial amount of nonmagnetic Fe4+ in the compound across the magnetic transition. The CP peak height across the magnetic transition increases substantially after annealing the …

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A Neutron Diffraction Study Of The Deuterium Site Occupancy In Nd5fe17d15.5, Z. Chu, William B. Yelon, R. K. Murakami, P. S.M. Da Silva, V. Villas-Boas, F. P. Missell Jan 2001

A Neutron Diffraction Study Of The Deuterium Site Occupancy In Nd5fe17d15.5, Z. Chu, William B. Yelon, R. K. Murakami, P. S.M. Da Silva, V. Villas-Boas, F. P. Missell

Physics Faculty Research & Creative Works

The intermetallic compound Nd5Fe17 has potentially important magnetic properties and is being investigated as a possible permanent magnetic material. As with many other rare-earth transition metal compounds, this phase can absorb significant quantities of H(D) and lesser amounts of N. Gravimetric measurement indicate that ∼14-16H(D) atoms can be absorbed per formula unit leading to roughly a 20% increase in saturation magnetization and Curie temperature. We have carried out powder neutron diffraction studies to determine the location of D atoms in a sample of Nd5Fe17 containing approximately 15.5D/f.u. The large, complex unit cell of Nd …

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Dynamics Of The Fragmentation Of D2 By Fast Protons And Slow Highly Charged Xe26+, I. Ali, Robert D. Dubois, C. L. Cocke, S. Hagmann, C. R. Feeler, Ronald E. Olson Jan 2001

Dynamics Of The Fragmentation Of D2 By Fast Protons And Slow Highly Charged Xe26+, I. Ali, Robert D. Dubois, C. L. Cocke, S. Hagmann, C. R. Feeler, Ronald E. Olson

Physics Faculty Research & Creative Works

Using recoil-ion momentum spectroscopy, combined with a multihit detector system, the full momentum vectors of both fragment ions produced by fragmentation of D2 by fast 50-kV protons and slow (9.56–0.191 keV/u) keV/u! Xe26+ ions have been measured. The data are kinematically complete and make it possible to separate the laboratory momentum of the center of mass of the molecule from the momentum of each fragment in the center-of-mass system of the molecule. Using this separation, we find that, for higher collision velocities, the overall reaction can be described as double-electron capture, followed in a second and separate step …

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Crystal And Magnetic Structure Of Pr0.7sr0.3-Xmno3 (0 ≤ X ≤ 0.2) Compounds, Q. Cai, William B. Yelon, M. Ellouze, W. Boujelben, A. Cheikh-Rouhou Jan 2001

Crystal And Magnetic Structure Of Pr0.7sr0.3-Xmno3 (0 ≤ X ≤ 0.2) Compounds, Q. Cai, William B. Yelon, M. Ellouze, W. Boujelben, A. Cheikh-Rouhou

Physics Faculty Research & Creative Works

The electronic and magnetic properties of the ABO3 type manganite's (A = rare earth, B = Mn) depend sensitively on the ratio of divalent and trivalent atoms on the A sublattice. The substitution of rare-earth by Ca or Sr not only affects the total valence, but also the lattice spacing, which, in turn may affect the structure and magnetic ordering temperature. If these compounds are synthesized with less than stoichiometric amounts of the A site constituents, (relative to the Mn content), three possible outcomes may be considered: a) single phase materials with vacancies on the A sublattice may be formed, …

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Electronic Structures And Magnetism Of Lani₅₋ₓfeₓ Compounds, Jinbo Yang, Chiu-Ying Tai, G. K. Marasinghe, George Daniel Waddill, Oran Allan Pringle, William Joseph James Jan 2001

Electronic Structures And Magnetism Of Lani₅₋ₓfeₓ Compounds, Jinbo Yang, Chiu-Ying Tai, G. K. Marasinghe, George Daniel Waddill, Oran Allan Pringle, William Joseph James

Physics Faculty Research & Creative Works

A systematic study of the magnetic moments and hyperfine interactions of the LaNi5-xFex compounds was performed using the spin-polarized tight-binding-linear-muffin-tin-orbital methods (TBLMTO). The calculated results were compared with neutron diffraction and Mössbauer experimental data and found to be in good agreement. Fe atoms exhibit more localized magnetic moments in LaNi5-xFex when the Fe content x is lower than 1.0. The calculated magnetic moments of the Fe atoms approach values as large as 2.5μB due to the dilution effect. The strong s-d hybridization between the Ni and La atoms and the neighboring Fe in …

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Three-Body Effects In The Fragmentation Of D2 By Slow, Highly-Charged Xenon, Robert D. Dubois, I. Ali, C. L. Cocke, C. R. Feeler, Ronald E. Olson Dec 2000

Three-Body Effects In The Fragmentation Of D2 By Slow, Highly-Charged Xenon, Robert D. Dubois, I. Ali, C. L. Cocke, C. R. Feeler, Ronald E. Olson

Physics Faculty Research & Creative Works

Highly charged xenon ions were used for fragmentation of D2 and the corresponding kinematic data. five-body classical trajectory Monte Carlo calculations were presented. Two types of three body effects were identified for strong collisions. Interactions between the undissociated molecules and the dipole fields of the projectiles were also found compatible with the fragmentation picture. Quadrupole-like and higher multipole interactions were the result of the differences between the dissociating fragments and the projectile fields.

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Transport Anomalies And Marginal Fermi-Liquid Effects At A Quantum Critical Point, Dietrich Belitz, Theodore R. Kirkpatrick, Rajesh S. Narayanan, Thomas Vojta Nov 2000

Transport Anomalies And Marginal Fermi-Liquid Effects At A Quantum Critical Point, Dietrich Belitz, Theodore R. Kirkpatrick, Rajesh S. Narayanan, Thomas Vojta

Physics Faculty Research & Creative Works

The conductivity and the tunneling density of states of disordered itinerant electrons in the vicinity of a ferromagnetic transition at low temperature are discussed. Critical fluctuations lead to nonanalytic frequency and temperature dependencies that are distinct from the usual long-time tail effects in a disordered Fermi liquid. The crossover between these two types of behavior is proposed as an experimental check of recent theories of the quantum ferromagnetic critical behavior. In addition, the quasiparticle properties at criticality are shown to be those of a marginal Fermi liquid.

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Binary Condensation In A Supersonic Nozzle, Barbara Ellen Wyslouzil, Christopher H. Heath, Janice L. Cheung, Gerald Wilemski Nov 2000

Binary Condensation In A Supersonic Nozzle, Barbara Ellen Wyslouzil, Christopher H. Heath, Janice L. Cheung, Gerald Wilemski

Physics Faculty Research & Creative Works

We present data from the first systematic studies of binary condensation in supersonic nozzles. The apparatus used to conduct the experiments is described in detail, and the important issues of stability and reproducibility of the experiments are discussed. Experiments were conducted with water, ethanol, propanol, and binary mixtures of these compounds. Onset was determined in the temperature range of 190-215 K, and for each mixture composition the pressures of the condensible species at an onset temperature of 207 K were determined. For the ideal ethanol-propanol mixtures, the onset pressures at constant temperature vary almost linearly between those of the pure …

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Resummation Of Nonalternating Divergent Perturbative Expansions, Ulrich D. Jentschura Oct 2000

Resummation Of Nonalternating Divergent Perturbative Expansions, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

A method for the resummation of a nonalternating divergent perturbation series is described. The procedure constitutes a generalization of the Borel-Padã method. Of crucial importance is a special integration contour in the complex plane. Nonperturbative imaginary contributions can be inferred from the purely real perturbative coefficients. A connection is drawn from the quantum field theoretic problem of resummation to divergent perturbative expansions in other areas of physics.

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Ionization Of Hydrogen Atoms By Fast Electrons, Sindu P. Jones, Don H. Madison Oct 2000

Ionization Of Hydrogen Atoms By Fast Electrons, Sindu P. Jones, Don H. Madison

Physics Faculty Research & Creative Works

We study ionization of atomic hydrogen by fast electrons using asymptotically correct two-center wave functions to describe the scattering system both initially and finally. For the final state, we employ the well-known product wave function of Redmond, which treats all three two-body Coulomb interactions exactly, albeit independently. This "3C" wave function is the leading term of the exact scattering wave function, regardless of how slow the three particles are, if any two particles have large relative separation [Y.E. Kim and A.L. Zubarev, Phys. Rev. A 56, 521 (1997)]. Here we extend the analysis of Qiu et al. [Phys. Rev. A …

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Resummation Of Qed Perturbation Series By Sequence Transformations And The Prediction Of Perturbative Coefficients, Ulrich D. Jentschura, Jens Becher, Ernst Joachim Weniger, Gerhard Soff Sep 2000

Resummation Of Qed Perturbation Series By Sequence Transformations And The Prediction Of Perturbative Coefficients, Ulrich D. Jentschura, Jens Becher, Ernst Joachim Weniger, Gerhard Soff

Physics Faculty Research & Creative Works

We propose a method for the resummation of divergent perturbative expansions in quantum electrodynamics and related field theories. The method is based on a nonlinear sequence transformation and uses as input data only the numerical values of a finite number of perturbative coefficients. The results obtained in this way are for alternating series superior to those obtained using Padé approximants. The nonlinear sequence transformation fulfills an accuracy-through-order relation and can be used to predict perturbative coefficients. In many cases, these predictions are closer to available analytic results than predictions obtained using the Padé method.

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Short-Pulse Laser-Induced Stabilization Of Autoionizing States, Heider N. Ereifej, J. Greg Story Sep 2000

Short-Pulse Laser-Induced Stabilization Of Autoionizing States, Heider N. Ereifej, J. Greg Story

Physics Faculty Research & Creative Works

Atoms in doubly excited states above the first ionization limit can decay via autoionization in which an electron is emitted leaving an ion, or by photoemission which leaves the atom in a singly excited state. In this paper, it is demonstrated that interaction between the atoms and a laser pulse that is short compared to the autoionization lifetime can lead to large enhancement of the photoemission process by stimulating the atoms to emit a photon. Since the resultant singly excited atoms do not autoionize, this process can be viewed as an enhancement of the stabilization of the doubly excited atoms …

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Concept Of Local Polaritons And Optical Properties Of Mixed Polar Crystals, Lev I. Deych, Alexey Yamilov, Alexander A. Lisyansky Sep 2000

Concept Of Local Polaritons And Optical Properties Of Mixed Polar Crystals, Lev I. Deych, Alexey Yamilov, Alexander A. Lisyansky

Physics Faculty Research & Creative Works

The concept of local polaritons is used to describe the optical properties of mixed crystals in the frequency region of their restrahlen band. It is shown that this concept allows for a physically transparent explanation of the presence of weak features in the spectra of so-called one-mode crystals and for one-two mode behavior. The previous models Were able to explain these features only with the use of many fitting parameters. We show that under certain Conditions new impurity-induced polariton modes may arise within the restrahlen of the host crystals, and study their dispersion laws and density of states. Particularly, we …

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Observation Of Stratospheric Ozone Depletion Associated With Delta Ii Rocket Emissions, Martin N. Ross, Darin W. Toohey, W. T. Rawlins, E. C. Richard, K. K. Kelly, A. F. Tuck, M. H. Proffitt, Donald E. Hagen, Alfred R. Hopkins, Philip D. Whitefield, J. R. Benbrook, W. R. Sheldon Aug 2000

Observation Of Stratospheric Ozone Depletion Associated With Delta Ii Rocket Emissions, Martin N. Ross, Darin W. Toohey, W. T. Rawlins, E. C. Richard, K. K. Kelly, A. F. Tuck, M. H. Proffitt, Donald E. Hagen, Alfred R. Hopkins, Philip D. Whitefield, J. R. Benbrook, W. R. Sheldon

Physics Faculty Research & Creative Works

Ozone, chlorine monoxide, methane, and submicron particulate concentrations were measured in the stratospheric plume wake of a Delta II rocket powered by a combination of solid (NH4ClO4/Al) and liquid (LOX/kerosene) propulsion systems. We apply a simple kinetics model describing the main features of gas-phase chlorine reactions in solid propellant exhaust plumes to derive the abundance of total reactive chlorine in the plume and estimate the associated cumulative ozone loss. Measured ozone loss during two plume encounters (12 and 39 minutes after launch) exceeded the estimate by about a factor of about two. Insofar as only the …

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Final Quantum Nf State Analysis For Multiply Charged Ion-Circular Rydberg Target Collisions, K. R. Cornelius, Ronald E. Olson Jul 2000

Final Quantum Nf State Analysis For Multiply Charged Ion-Circular Rydberg Target Collisions, K. R. Cornelius, Ronald E. Olson

Physics Faculty Research & Creative Works

The classical trajectory Monte Carlo method has been used to simulate fully stripped ion-circular Rydberg atom collisions. We report that the mechanisms that govern the capture process for ions colliding with aligned Rydberg targets, namely direct and indirect velocity matching, alternate as to which is dominant. Previous experimental and theoretical results for singly charged ion-Rydberg atom collisions demonstrate that direct capture processes dominate at intermediate collision speeds. We have found that for highly charged ion-Rydberg atom collisions electron capture via indirect velocity matching is dominant at intermediate collision speeds and contributes up to 90% of the total capture cross-section.

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Direct Measurement Of Oscillations Between Degenerate Two-Electron Bound-State Configurations In A Rapidly Autoionizing System, Heider N. Ereifej, J. Greg Story Jul 2000

Direct Measurement Of Oscillations Between Degenerate Two-Electron Bound-State Configurations In A Rapidly Autoionizing System, Heider N. Ereifej, J. Greg Story

Physics Faculty Research & Creative Works

In this paper we report a direct observation of the oscillation between bound-state configurations in a rapidly autoionizing system. Calcium atoms were excited to a pure 4p3/2nd two-electron configuration using a 500-fsec laser pulse. The initial 4p3/2nd doubly excited state is energy degenerate with the 4p1/2n'd states and several continuum channels. Because of the short-pulse excitation, the initial state of the atom is not an energy eigenstate, but a nonstationary wave packet. As a result, oscillations between the two bound configurations were produced. These oscillations were measured by scanning the timing of a second …

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Neutral Beam Stopping And Emission In Fusion Plasmas. I: Deuterium Beams, H. Anderson, M. G. Von Hellermann, R. Hoekstra, L. D. Horton, A. C. Howman, R. W.T. Konig, R. Martin, Ronald E. Olson, H. P. Summers Jul 2000

Neutral Beam Stopping And Emission In Fusion Plasmas. I: Deuterium Beams, H. Anderson, M. G. Von Hellermann, R. Hoekstra, L. D. Horton, A. C. Howman, R. W.T. Konig, R. Martin, Ronald E. Olson, H. P. Summers

Physics Faculty Research & Creative Works

The charge transfer reaction of neutral deuterium beams with impurities enables one of the principle quantitative diagnostic measurements of the hot core fusion plasma; that is, charge exchange spectroscopy. The complementary measurement of beam emission spectroscopy has been fruitful in motional Stark wavelength shift and fluctuation studies, but less so in using absolute measured intensities. In the last two years we have achieved substantial improvement in the quantitative analysis and agreement between the observed and modelled beam emission at the JET Joint Undertaking. This has depended on improved spectral fitting of the overlayed Dα motional Stark multiplet, self-consistent beam emission …

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State-Selective Cross Section Scalings For Electron Capture Collisions, K. R. Cornelius, K. Wojtkowski, Ronald E. Olson Jun 2000

State-Selective Cross Section Scalings For Electron Capture Collisions, K. R. Cornelius, K. Wojtkowski, Ronald E. Olson

Physics Faculty Research & Creative Works

The classical-trajectory Monte Carlo method is used to calculate total and final nf state-selective electron capture cross sections for various fully stripped ions, ranging from He2+ to Ne10+, incident on H(ni = 1-4) and Li(2s and 2p) targets over the collision energies of 1-100 keV u-1. Theoretical derivations of two scaling laws for state-selective electron capture cross sections as a function of collision energy, initial and final bound electron states and projectile charge are presented. The new scaling rules reduce the state-selective capture cross sections to very distinct universal curves. Curve fits …

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Single Ionization Of Ne By Intense Laser Fields, C. R. Feeler, Ronald E. Olson Jun 2000

Single Ionization Of Ne By Intense Laser Fields, C. R. Feeler, Ronald E. Olson

Physics Faculty Research & Creative Works

A three-dimensional classical Monte Carlo method has been used to examine the final state electron dynamics after single ionization of neon in an electric field generated by a short-pulse high-intensity laser. Linearly and circularly polarized fields were studied. Intensities ranging from 3 x 1014 to 3 x 1015 W cm-2 were used with a wavelength of 800 nm and a full-width at half-maximum of 30 fs. At these values, the Keldysh parameter is less than one, making the classical approximation valid. A potential determined by Hartree-Fock calculations has been used to model the Ne atom. A kinematically complete picture …

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Genuine Saddle Point And Nucleation Potential For Binary Systems, Jinsong Li, Igor L. Maksimov, Gerald Wilemski May 2000

Genuine Saddle Point And Nucleation Potential For Binary Systems, Jinsong Li, Igor L. Maksimov, Gerald Wilemski

Physics Faculty Research & Creative Works

A generalized nucleation potential is constructed for binary systems. The potential consists of the reversible work of cluster formation plus additional terms arising from various kinetic effects. We show that the major nucleation flux passes through the saddle point (termed the genuine saddle point) of this generalized nucleation potential. The generalized nucleation potential reduces to the kinetic potential of a unary system when one component vanishes. The genuine saddle point concept provides a convenient way to identify systems and conditions for which the ridge crossing phenomenon occurs. Our theory agrees approximately with exact numerical results.

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Annealed Disorder, Rare Regions, And Local Moments: A Novel Mechanism For Metal-Insulator Transitions, Dietrich Belitz, Theodore R. Kirkpatrick, Thomas Vojta May 2000

Annealed Disorder, Rare Regions, And Local Moments: A Novel Mechanism For Metal-Insulator Transitions, Dietrich Belitz, Theodore R. Kirkpatrick, Thomas Vojta

Physics Faculty Research & Creative Works

It is shown that, for noninteracting electron systems, annealed magnetic disorder leads to a new mechanism, and a new universality class, for a metal-insulator transition. The transition is driven by a vanishing of the thermodynamic density susceptibility rather than by localization effects. The critical behavior in d = 2 + ∈ dimensions is determined, and the underlying physics is discussed. It is further argued that annealed magnetic disorder, in addition to underlying quenched disorder, describes local magnetic moments in electronic systems.

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Photoelectron Diffraction Determination Of The Structure Of Ultrathin Vanadium Films On Cu(001), George Daniel Waddill, D. P. Moore, Osman Ozturk Mar 2000

Photoelectron Diffraction Determination Of The Structure Of Ultrathin Vanadium Films On Cu(001), George Daniel Waddill, D. P. Moore, Osman Ozturk

Physics Faculty Research & Creative Works

X-ray photoelectron diffraction (XPD) and low-energy electron diffraction (LEED) have been used to study the structural properties of V thin films on Cu(001). For room-temperature growth, submonolayer coverages result in (1x1) LEED patterns that evolve to exhibit very diffuse (2x1) structure at approximately 1 monolayer coverage. We do not observe any V forward-focusing enhancements for V films that exhibit either the (1x1) or (2x1) structure, suggesting that these structures are limited to the first 1-2 vanadium layers. At coverages above 1 monolayer, the V films display complex LEED patterns characteristic of four bcc(110) domains. This structure persists to V coverages …

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Quantum Gravity Corrections To The Schwarzschild Mass, Marco Cavaglia, Carlo Ungarelli Feb 2000

Quantum Gravity Corrections To The Schwarzschild Mass, Marco Cavaglia, Carlo Ungarelli

Physics Faculty Research & Creative Works

Vacuum spherically symmetric Einstein gravity in (N≥4) dimensions can be cast in a two-dimensional conformal nonlinear sigma model form by first integrating on the (N - 2)-dimensional (hyper)sphere and then performing a canonical transformation. The conformal sigma model is described by two fields which are related to the Arnowitt-Deser-Misner (ADM) mass and to the radius of the (N - 2)-dimensional (hyper)sphere, respectively. By quantizing perturbatively the theory we estimate the quantum corrections to the ADM mass of a black hole.

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Observations Of Particulates Within The North Atlantic Flight Corridor: Polinat 2, September-October 1997, J. D. Paladino, Donald E. Hagen, Philip D. Whitefield, Alfred Raymond Hopkins, Otmar Schmid, M. R. Wilson, Hans Schlager, Peter Schulte Feb 2000

Observations Of Particulates Within The North Atlantic Flight Corridor: Polinat 2, September-October 1997, J. D. Paladino, Donald E. Hagen, Philip D. Whitefield, Alfred Raymond Hopkins, Otmar Schmid, M. R. Wilson, Hans Schlager, Peter Schulte

Physics Faculty Research & Creative Works

This paper discusses particulate concentration and size distribution data gathered using the University of Missouri-Rolla Mobile Aerosol Sampling System (UMR-MASS), and used to investigate the southern extent of the eastern end of the North Atlantic Flight Corridor (NAFC) during project Pollution From Aircraft Emissions in the North Atlantic Flight Corridor/Subsonic Assessment (SASS) Ozone and Nitrogen Oxide Experiment (POLINAT 2/SONEX) from September 19 to October 23, 1997. The analysis presented in this paper focuses on "the corridor effect," or enhancement of pollutants by jet aircraft combustion events. To investigate the phenomena, both vertical and horizontal profiles of the corridor, and regions …

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Correlated Three-Electron Continuum States In Triple Ionization By Fast Heavy-Ion Impact, Michael Schulz, Robert Moshammer, Wayne M. Schmitt, Holger Kollmus, Rido Mann, Siegbert Hagmann, Ronald E. Olson, Joachim Hermann Ullrich Feb 2000

Correlated Three-Electron Continuum States In Triple Ionization By Fast Heavy-Ion Impact, Michael Schulz, Robert Moshammer, Wayne M. Schmitt, Holger Kollmus, Rido Mann, Siegbert Hagmann, Ronald E. Olson, Joachim Hermann Ullrich

Physics Faculty Research & Creative Works

We have performed a kinematically complete experiment for triple ionization in atomic collisions. Data were obtained for 3.6-MeV/amu Au53+ impact on Ne. A specific Dalitz representation was developed allowing one to plot in a single spectrum the energy of all three ionized electrons and, simultaneously, obtain information on their emission angles with respect to the projectile direction. The data show distinct fragmentation patterns favoring very asymmetric energy partitionings with one fast and two slow electrons. They are compared to various Classical Trajectory Monte Carlo (CTMC) models. The experimental results are well described only if the electron-electron interaction is included …

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