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Full-Text Articles in Physics

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 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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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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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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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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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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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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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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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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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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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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Excitation Of Ar 3p⁵4s-3p⁵4p Transitions By Electron Impact, Colette M. Maloney, Jerry Peacher, Klaus Bartschat, Don H. Madison Feb 2000

Excitation Of Ar 3p⁵4s-3p⁵4p Transitions By Electron Impact, Colette M. Maloney, Jerry Peacher, Klaus Bartschat, Don H. Madison

Physics Faculty Research & Creative Works

Electron-impact excitation of argon from the 3p54s (J=0,2) metastable states to the 3p54p (J=0,1,2,3) manifold has been investigated in the semirelativistic first-order distorted-wave and plane-wave Born approximations. The results are compared with recent experimental data of Boffard et al. [Phys. Rev. A 59, 2749 (1999)] and R-matrix predictions by Bartschat and Zeman [Phys. Rev. A 59, R2552 (1999)]. In cases for which perturbative approaches are expected to be valid, the plane-wave Born approximation is found to be sufficiently accurate and thus allows for an efficient calculation of results over a wide range of collision energies.

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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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Neutron Scattering From Aerosols: Intraparticle Structure Factor, Guinier Analysis Of Particle Speed, And Crossed Beam Kinematics, Gerald Wilemski Jan 2000

Neutron Scattering From Aerosols: Intraparticle Structure Factor, Guinier Analysis Of Particle Speed, And Crossed Beam Kinematics, Gerald Wilemski

Physics Faculty Research & Creative Works

A theoretical formalism for neutron scattering from systems of particles is applied to liquid nanodroplet aerosols. A term arising from intraparticle, intermolecular correlations is identified. The kinematical theory of two body scattering is recast into a form convenient for interpreting the results of experiments with crossed beams of neutrons and aerosol particles. Based on a theoretical analysis of the scattered intensity in the Guinier region, a method for determining the particle velocity directly from the experimental data is outlined. The method is not restricted by assumptions about particle shape, composition, uniformity, or size distribution.

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Electron Correlations Observed Through Intensity Interferometry, Michael Schulz, Robert Moshammer, Wayne M. Schmitt, Holger Kollmus, Bernold Feuerstein, Rido Mann, Siegbert Hagmann, Joachim Hermann Ullrich Jan 2000

Electron Correlations Observed Through Intensity Interferometry, Michael Schulz, Robert Moshammer, Wayne M. Schmitt, Holger Kollmus, Bernold Feuerstein, Rido Mann, Siegbert Hagmann, Joachim Hermann Ullrich

Physics Faculty Research & Creative Works

Intensity interferometry was applied to study electron correlations in doubly ionizing ion-atom collisions. In this method, the probability to find two electrons emitted in the same double ionization event with a certain momentum difference is compared to the corresponding probability for two uncorrelated electrons from two independent events. The ratio of both probabilities, the so-called correlation function, is found to sensitively reveal electron correlation effects, but it is rather insensitive to the collision dynamics.

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Crystal And Magnetic Structures Of Lani₅₋ₓmnₓ, Chiu-Ying Tai, G. K. Marasinghe, Oran Allan Pringle, William Joseph James, Muguo Chen, William B. Yelon, I. Dubenko, Naushad Ali, Ph. I'Héritier Jan 2000

Crystal And Magnetic Structures Of Lani₅₋ₓmnₓ, Chiu-Ying Tai, G. K. Marasinghe, Oran Allan Pringle, William Joseph James, Muguo Chen, William B. Yelon, I. Dubenko, Naushad Ali, Ph. I'Héritier

Physics Faculty Research & Creative Works

The crystallographic and magnetic properties of LaN5-xMnx with x = 1, 1.5, and 2, have been investigated using x-ray and neutron diffraction, vibrating sample magnetometer and superconducting quantum interference device measurements. All the samples crystallize in the hexagonal CaCu5-type (P6/mmm) structure. Manganese atoms preferentially occupy the 3 g site in the LaNi5 structure. The bulk magnetization of the LaNi5-xMnx powder samples decreases rapidly as nickel is replaced by manganese. A ferrimagnetic model is applied to describe the magnetic structure of the LaNi5-xMnx samples for x = 1.5 and …

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Initial State Dependence Of Low-Energy Electron Emission In Fast Ion Atom Collisions, Robert Moshammer, Pablo Daniel Fainstein, Michael Schulz, Wayne M. Schmitt, Holger Kollmus, Rido Mann, Siegbert Hagmann, Joachim Hermann Ullrich Dec 1999

Initial State Dependence Of Low-Energy Electron Emission In Fast Ion Atom Collisions, Robert Moshammer, Pablo Daniel Fainstein, Michael Schulz, Wayne M. Schmitt, Holger Kollmus, Rido Mann, Siegbert Hagmann, Joachim Hermann Ullrich

Physics Faculty Research & Creative Works

Single and multiple ionization of neon and argon atoms by 3.6 MeV/u Au53+ impact has been explored in kinematically complete experiments. Doubly differential cross sections for low-energy electron emission have been obtained for a defined charge state of the recoiling target ion and the receding projectile. Observed target specific structures in the electron continuum are attributable to the nodal structure of the initial bound state momentum distribution. The experimental data are in excellent accord with continuum-distorted-wave eikonal-initial-state single ionization calculations if multiple ionization is considered appropriately.

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Laser-Induced Stabilization Of Autoionizing States, Heider N. Ereifej, J. Greg Story Nov 1999

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

Physics Faculty Research & Creative Works

Stabilization of autoionizing states of barium by laser-induced, stimulated emission of light is demonstrated. Relative to purely flourescent stabilization, the data clearly show an enhancement of the stabilization process for laser pulses short compared to the flourescent lifetime of the autoionizing states. Shakeup spectra in which the principal quantum number of both electrons changes during the stimulated emission process are also clearly demonstrated.

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Doppler Shift Anisotropy In Small Angle Neutron Scattering, Barbara Ellen Wyslouzil, Gerald Wilemski, Janice L. Cheung, Reinhard Strey, John G. Barker Oct 1999

Doppler Shift Anisotropy In Small Angle Neutron Scattering, Barbara Ellen Wyslouzil, Gerald Wilemski, Janice L. Cheung, Reinhard Strey, John G. Barker

Physics Faculty Research & Creative Works

The two-dimensional patterns in our small angle neutron scattering (SANS) experiments from rapidly moving aerosols are anisotropic. To test the kinematic theory of two-body scattering that describes the anisotropy, we conducted SANS experiments using a constant source of D2O aerosol with droplets moving at ~440 m/s, and varied the neutron velocity from 267 to 800 m/s. The theoretically predicted anisotropy of the laboratory scattering intensities agrees well with the experimental results. Based on an analysis of the scattering intensity in the Guinier region, we also determined the particle velocity. The results are in very good agreement with independent …

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Critical Behavior Of Disordered Quantum Magnets: The Relevance Of Rare Regions, Rajesh S. Narayanan, Thomas Vojta, Dietrich Belitz, Theodore R. Kirkpatrick Oct 1999

Critical Behavior Of Disordered Quantum Magnets: The Relevance Of Rare Regions, Rajesh S. Narayanan, Thomas Vojta, Dietrich Belitz, Theodore R. Kirkpatrick

Physics Faculty Research & Creative Works

The effects of quenched disorder on the critical properties of itinerant quantum antiferromagnets and ferromagnets are considered. Particular attention is paid to locally ordered spatial regions that are formed in the presence of quenched disorder even when the bulk system is still in the paramagnetic phase. These rare regions or local moments are reflected in the existence of spatially inhomogeneous saddle points of the Landau-Ginzburg-Wilson functional. We derive an effective theory that takes into account small fluctuations around all of these saddle points. The resulting free energy functional contains a new term in addition to those obtained within the conventional …

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Investigation Of Resonant Photoemission In Gd With X-Ray Linear Dichroism, Shubhra R. Mishra, Thomas K. Cummins, George Daniel Waddill, W. J. Gammon, Gerrit V. Van Der Laan, Kyle W. Goodman, James G. Tobin Jul 1999

Investigation Of Resonant Photoemission In Gd With X-Ray Linear Dichroism, Shubhra R. Mishra, Thomas K. Cummins, George Daniel Waddill, W. J. Gammon, Gerrit V. Van Der Laan, Kyle W. Goodman, James G. Tobin

Physics Faculty Research & Creative Works

The constructive summing of direct and indirect channels above the absorption threshold of a core level can cause a massive increase in the emission cross section, leading to a phenomenon called "resonant photoemission." Using novel magnetic linear dichroism in angular distribution photoelectron spectroscopy experiments and theoretical simulations, we have probed the nature of the resonant photoemission process in Gd metal. It now appears that temporal matching as well as energy matching is a requirement for true resonant photoemission.

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Influence Of Rare Regions On Magnetic Quantum Phase Transitions, Rajesh S. Narayanan, Thomas Vojta, Dietrich Belitz, Theodore R. Kirkpatrick Jun 1999

Influence Of Rare Regions On Magnetic Quantum Phase Transitions, Rajesh S. Narayanan, Thomas Vojta, Dietrich Belitz, Theodore R. Kirkpatrick

Physics Faculty Research & Creative Works

The effects of quenched disorder on the critical properties of itinerant quantum magnets are considered. Particular attention is paid to locally ordered rare regions that are formed in the presence of quenched disorder even when the bulk system is still in the nonmagnetic phase. It is shown that these local moments or instantons destroy the previously found critical fixed point in the case of antiferromagnets. In the case of itinerant ferromagnets, the critical behavior is unaffected by the rare regions due to an effective long-range interaction between the order parameter fluctuations.

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First Order Transitions And Multicritical Points In Weak Itinerant Ferromagnets, Dietrich Belitz, Theodore R. Kirkpatrick, Thomas Vojta Jun 1999

First Order Transitions And Multicritical Points In Weak Itinerant Ferromagnets, Dietrich Belitz, Theodore R. Kirkpatrick, Thomas Vojta

Physics Faculty Research & Creative Works

It is shown that the phase transition in low-Tc clean itinerant ferromagnets is generically of first order, due to correlation effects that lead to a nonanalytic term in the free energy. A tricritical point separates the line of first order transitions from Heisenberg critical behavior at higher temperatures. Sufficiently strong quenched disorder suppresses the first order transition via the appearance of a critical end point. A semiquantitative discussion is given in terms of recent experiments on MnSi, and predictions for other experiments are made.

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Defect-Induced Resonant Tunneling Of Electromagnetic Waves Through A Polariton Gap, Lev I. Deych, Alexey Yamilov, Alexander A. Lisyansky May 1999

Defect-Induced Resonant Tunneling Of Electromagnetic Waves Through A Polariton Gap, Lev I. Deych, Alexey Yamilov, Alexander A. Lisyansky

Physics Faculty Research & Creative Works

We consider tunneling of electromagnetic waves through a polariton band gap of a 1-D chain of atoms. We analytically demonstrate that a defect embedded in the structure gives rise to the resonance transmission at the frequency of a local polariton state associated with the defect.

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Effects Of Resonant Tunneling In Electromagnetic Wave Propagation Through A Polariton Gap, Lev I. Deych, Alexey Yamilov, Alexander A. Lisyansky May 1999

Effects Of Resonant Tunneling In Electromagnetic Wave Propagation Through A Polariton Gap, Lev I. Deych, Alexey Yamilov, Alexander A. Lisyansky

Physics Faculty Research & Creative Works

We consider tunneling of electromagnetic waves through a polariton band gap of a one-dimensional chain of atoms. We analytically show that a defect embedded in the structure gives rise to the resonance transmission at the frequency of a local polariton state associated with the defect. Numerical Monte Carlo simulations are used to examine properties of the electromagnetic band arising inside the polariton gap due to finite concen-tration of defects.

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Binary Nucleation Kinetics. Iv. Directional Properties And Cluster Concentrations At The Saddle Point, Gerald Wilemski Apr 1999

Binary Nucleation Kinetics. Iv. Directional Properties And Cluster Concentrations At The Saddle Point, Gerald Wilemski

Physics Faculty Research & Creative Works

Using a new approach, Stauffer's expression for the rate of steady state binary nucleation and Trinkaus's expression for the steady state cluster concentrations f are derived directly from the diffusion equation that governs the evolution of f in composition space. The behavior of φ (≡f/N, where N is the equilibrium cluster concentration) is explored since this function provides a characterization of the nucleating binary system that, to lowest order, is independent of the actual composition of the mother phase. The angle ω that describes the direction of ▽ φ at the saddle point differs, in general, from the angle φ …

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Geometrodynamical Formulation Of Two-Dimensional Dilaton Gravity, Marco Cavaglia Mar 1999

Geometrodynamical Formulation Of Two-Dimensional Dilaton Gravity, Marco Cavaglia

Physics Faculty Research & Creative Works

Two-dimensional matterless dilaton gravity with an arbitrary dilatonic potential can be discussed in a unitary way, both in the Lagrangian and canonical frameworks, by introducing suitable field redefinitions. The new fields are directly related to the original spacetime geometry and in the canonical picture they generalize the well-known geometrodynamical variables used in the discussion of the Schwarzschild black hole. So the model can be quantized using the techniques developed for the latter case. The resulting quantum theory exhibits the Birkhoff theorem at the quantum level.

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Magnetic And Crystallographic Properties Of Lani₅₋ₓfex, C. Tan, Oran Allan Pringle, Mingxing Chen, William B. Yelon, J. Gebhardt, Naushad Ali, C. Y. Tai, G. K. Marasinghe, George Daniel Waddill, William Joseph James Jan 1999

Magnetic And Crystallographic Properties Of Lani₅₋ₓfex, C. Tan, Oran Allan Pringle, Mingxing Chen, William B. Yelon, J. Gebhardt, Naushad Ali, C. Y. Tai, G. K. Marasinghe, George Daniel Waddill, William Joseph James

Physics Faculty Research & Creative Works

No abstract provided.

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X-Ray Absorption, Neutron Diffraction, And Mössbauer Effect Studies Of Mnzn-Ferrite Processed Through High-Energy Ball Milling, D. J. Fatemi, V. G. Harris, Mingxing Chen, Satish K. Malik, William B. Yelon, Gary J. Long, Amitabh Mohan Jan 1999

X-Ray Absorption, Neutron Diffraction, And Mössbauer Effect Studies Of Mnzn-Ferrite Processed Through High-Energy Ball Milling, D. J. Fatemi, V. G. Harris, Mingxing Chen, Satish K. Malik, William B. Yelon, Gary J. Long, Amitabh Mohan

Physics Faculty Research & Creative Works

MnZn-ferrite has been prepared via high-energy ball milling of elemental oxides MnO, ZnO, and α-Fe2O3. Neutron diffraction measurements suggest a high density of vacancies in a spinel structure. The spinel phase appears to comprise 99.8 wt % of the material in the sample milled for 40 h, with the remainder attributable to unreacted α-Fe2O3. The x-ray absorption near-edge structure was analyzed to provide an understanding of the charge state of the constituent Fe ions. This analysis reveals about 2/3 of Fe cations to be trivalent, increasing to about 3/4 after a 5 …

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