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Full-Text Articles in Physics

Thermally Induced Core-Electron Binding-Energy Shifts In Transition Metals: An Experimentalinvestigation Of Ta(100), D. Mark Riffe, B. Kim, W. Hale, J. L. Erskine Dec 1996

Thermally Induced Core-Electron Binding-Energy Shifts In Transition Metals: An Experimentalinvestigation Of Ta(100), D. Mark Riffe, B. Kim, W. Hale, J. L. Erskine

All Physics Faculty Publications

High-resolution photoemission spectra from the 4f7/2 levels of Ta(100) have been obtained between 77 K and room temperature. The data show an increase in both the surface and bulk core-level binding energies (BE’s) as the temperature is raised: between 77 and 293 K the bulk and surface BE’s increase by 31±3 and 13±2 meV, respectively. A model calculation of the bulk binding-energy increase, which is based upon the lattice expansion of the solid, is in good agreement with the experimental results and indicates that the shifts arise from both initial- and final-state effects ...


Auroral Electrojet Irregularity Theory And Experiment: A Criticalreview Of Present Understanding And Future Directions, J. D. Sahr, Bela G. Fejer Dec 1996

Auroral Electrojet Irregularity Theory And Experiment: A Criticalreview Of Present Understanding And Future Directions, J. D. Sahr, Bela G. Fejer

Bela G. Fejer

We review the experimental observations of meter scale plasma irregularities in the auroral E region and the status of their theoretical understanding. Most of the experimental data is derived from VHF radar scatter experiments, but sounding rockets also provide crucial information not obtainable from radars. Linear theories correctly predict the altitude of occurence, strong magnetic aspect sensitivity, marginal instability, and typical phase velocities. Subsequent nonlinear theories have been developed to account for other observed features but with less satisfying application. Further understanding of auroral electrojet irregularities is impeded by precision limitations of existing instruments, by radar data which may seem ...


Building A Competition Buzzer Set, Jr Dennison, Richard Davis Dec 1996

Building A Competition Buzzer Set, Jr Dennison, Richard Davis

All Physics Faculty Publications

No abstract provided.


Asymptotic Conservation Laws In Field Theory, Ian M. Anderson, Charles G. Torre Nov 1996

Asymptotic Conservation Laws In Field Theory, Ian M. Anderson, Charles G. Torre

All Physics Faculty Publications

A new, general, field theoretic approach to the derivation of asymptotic conservation laws is presented. In this approach asymptotic conservation laws are constructed directly from the field equations according to a universal prescription which does not rely upon the existence of Noether identities or any Lagrangian or Hamiltonian formalisms. The resulting general expressions of the conservation laws enjoy important invariance properties and synthesize all known asymptotic conservation laws, such as the Arnowitt-Deser-Misner energy in general relativity.


Raman Spectroscopy Of Carbon Materials, Jr Dennison, M. Holtz, G. Swain Oct 1996

Raman Spectroscopy Of Carbon Materials, Jr Dennison, M. Holtz, G. Swain

All Physics Faculty Publications

Use of carbon materials is no longer limited to diamond jewelry or graphite pencils and lubricants. The last decade has witnessed an explosion of technological applications driven by the development of fabrication methods and the discovery of several new classes of pure carbon. Structural diversity exhibited by the carbon atoms, from local chemical order to long-range crystalline order, is key to understanding their physical and chemical properties and in future materials development. This article summarizes the use of Raman spectroscopy as a principal tool to investigate the vibrational dynamics of carbon materials and to provide indirect structural characterization of their ...


Observationsof Inner-Plasmasphere Irregularities With A Satellite Beacon Interferometer Array, A. R. Jacobsen, G. Hogeveen, R. C. Carlos, G. Wu, Bela G. Fejer, M. C. Kelley Sep 1996

Observationsof Inner-Plasmasphere Irregularities With A Satellite Beacon Interferometer Array, A. R. Jacobsen, G. Hogeveen, R. C. Carlos, G. Wu, Bela G. Fejer, M. C. Kelley

Bela G. Fejer

A radio-interferometer array illuminated by 136-MHz beacons of several geosynchronous satellites has been used to study small (≥ 1013 m−2) transient disturbances in the total electron content along the lines of sight to the satellites. High-frequency (ƒ> 3 mHz) electron content oscillations are persistently observed, particularly during night and particularly during geomagnetically disturbed periods. The oscillations move across the array plane at speeds in the range 200–2000 m/s, with propagation azimuths that are strongly peaked in lobes toward the western half-plane. Detailed analysis of this azimuth behavior, involving comparison between observations on various satellite positions, indicates compellingly that ...


Pattern Formation And Evolution Near Autocatalytic Reaction Fronts In A Narrow Vertical Slab, J. Huang, Boyd F. Edwards Sep 1996

Pattern Formation And Evolution Near Autocatalytic Reaction Fronts In A Narrow Vertical Slab, J. Huang, Boyd F. Edwards

All Physics Faculty Publications

Linear analysis and nonlinear numerical simulations of autocatalytic reaction fronts ascending in narrow vertically unbounded slabs describe the growth, development, and annihilation of fingers in the front, the dynamics of edge suppression, and a secondary transition to a two-roll state above the onset of convection. The pattern formation and evolution of the reaction fronts are determined by the horizontal aspect ratio Γ=b/a and the dimensionless driving parameter S=δga3/νDC, which involve the gap thickness a, the slab width b, the fractional density difference δ between the unreacted and reacted solutions, the gravitational acceleration g, the ...


Application Of (E,2e) Spectroscopy To The Electronic Structure Of Valence Electrons In Crystalline And Amorphous Solids, Jr Dennison, A. L. Ritter Aug 1996

Application Of (E,2e) Spectroscopy To The Electronic Structure Of Valence Electrons In Crystalline And Amorphous Solids, Jr Dennison, A. L. Ritter

All Physics Faculty Publications

This review presents theoretical and experimental aspects of (e,2e) spectroscopy specific to the study of crystalline and amorphous solids. The cross section for (e,2e) scattering is proportional to the spectral momentum density of the ejected electron under certain approximations. The theoretical framework for interpreting (e,2e) measurements is summarized here and general properties of the spectral momentum density of solids are discussed. Different designs of the (e,2e) spectrometer are described and sample preparation techniques are briefly reviewed. A summary of (e,2e) experiments on the electronic structure of valence electrons in graphite, ion sputtered and evaporated amorphous ...


Incoherent Scatter Radar, Ionosonde,And Satellite Measurements Of Equatorial F Region Vertical Plasma Drifts In The Evening Sector, Bela G. Fejer, E. R. De Paula, L. Scherliess, I. S. Batista Jul 1996

Incoherent Scatter Radar, Ionosonde,And Satellite Measurements Of Equatorial F Region Vertical Plasma Drifts In The Evening Sector, Bela G. Fejer, E. R. De Paula, L. Scherliess, I. S. Batista

Bela G. Fejer

Studies of equatorial F region evening vertical plasma drifts using different measurement techniques have produced conflicting results. We examine the relationship of incoherent scatter radar and ionosonde drift observations over the Peruvian equatorial region, and AE-E satellite drifts for different geophysical conditions. Our data show that there is large day-to-day variability on the ratios of radar and ionosonde drifts, but on the average the measurements from these two techniques are in fair agreement during low and moderate solar flux conditions. For high solar activity, however, the Jicamarca evening drifts during equinox and December solstice are significantly larger than the ionosonde ...


A Study Of The Gradient Drift Instability In The High-Latitude Ionosphere Using The Utah State University Time Dependent Ionospheric Model, Mahesh Subramanium May 1996

A Study Of The Gradient Drift Instability In The High-Latitude Ionosphere Using The Utah State University Time Dependent Ionospheric Model, Mahesh Subramanium

All Graduate Theses and Dissertations

Research over the years has established that the Gradient Drift Instability process causes small-scale irregularities, mostly along the edges of the high-latitude polar cap patches. Studying these irregularities will help in the development of a global Scale Ionospheric model, which is a central part of a global space weather forecast system. Much theoretical work has been done with varying degrees of complexity to study this instability in the high latitude patches.

In this work we have used the Utah State University Time Dependent Ionospheric Model to model the high-latitude patches, calculate the growth rate of the instability, and perform a ...


An Instrument For Experimental Secondary Electron Emission Investigations, With Application To The Spacecraft Charging Problem, Robert Davies May 1996

An Instrument For Experimental Secondary Electron Emission Investigations, With Application To The Spacecraft Charging Problem, Robert Davies

All Graduate Theses and Dissertations

Secondary electron emission (SEE) and incident-particle backscattering are important processes accompanying the impact of energetic electrons and ions on surfaces. The phenomena play a key role in the buildup of electrical charge on spacecraft surfaces, and are therefore of particular interest to scientists attempting to model spacecraft charging. In response to a demonstrated need for data, techniques for determining total secondary electron (SE) and backscatter (BS) yields (del) and (neu), and associated scattering-angle-resolved,scattering-energy-resolved, and simultaneous angle-energy-resolved yields have been developed. Further, an apparatus capable of making the necessary measurements for experimental determination of these quantities---for conducting materials in an ...


Chemical Wave Propagation In Hele-Shaw Cells And Porous Media, D. A. Vasquez, J. W. Wilder, Boyd F. Edwards Mar 1996

Chemical Wave Propagation In Hele-Shaw Cells And Porous Media, D. A. Vasquez, J. W. Wilder, Boyd F. Edwards

All Physics Faculty Publications

Chemical waves induce density gradients in fluids which may lead to convection. This paper studies the convective effects on chemical waves propagating in porous media or in fluids confined between two parallel vertical walls. Chemical waves in the iodate–arsenous acid system are modeled with a one variable reaction‐diffusion equation. The fluid flow is modeled using Darcy’s law. A linear stability analysis on convectionless fronts shows a transition to convection. The full nonlinear equations describing the convective front are solved numerically on a vertical slab. Convective fronts propagate faster than convectionless fronts. Near the onset of convection, the ...


Asymptotic Conservation Laws In Classical Field Theory, Ian M. Anderson, Charles G. Torre Jan 1996

Asymptotic Conservation Laws In Classical Field Theory, Ian M. Anderson, Charles G. Torre

Mathematics and Statistics Faculty Publications

A new, general, field theoretic approach to the derivation of asymptotic conservation laws is presented. In this approach asymptotic conservation laws are constructed directly from the field equations according to a universal prescription which does not rely upon the existence of Noether identities or any Lagrangian or Hamiltonian formalisms. The resulting general expressions of the conservation laws enjoy important invariance properties and synthesize all known asymptotic conservation laws, such as the Arnowitt-Deser-Misner energy in general relativity.


Application Of (E,2e) Spectroscopy To The Electronic Structure Of Valence Electrons In Crystalline And Amorphous Solids, Jr Dennison, A. L. Ritter Jan 1996

Application Of (E,2e) Spectroscopy To The Electronic Structure Of Valence Electrons In Crystalline And Amorphous Solids, Jr Dennison, A. L. Ritter

Journal Articles

This review presents theoretical and experimental aspects of (e,2e) spectroscopy specific to the study of crystalline and amorphous solids. The cross section for (e,2e) scattering is proportional to the spectral momentum density of the ejected electron under certain approximations. The theoretical framework for interpreting (e,2e) measurements is summarized here and general properties of the spectral momentum density of solids are discussed. Different designs of the (e,2e) spectrometer are described and sample preparation techniques are briefly reviewed. A summary of recent (e,2e) experiments on the electronic structure of valence electrons in graphite, ion sputtered and evaporated ...


Raman Spectroscopy Of Carbon Materials, Jr Dennison, Mark Holtz, Greg Swain Jan 1996

Raman Spectroscopy Of Carbon Materials, Jr Dennison, Mark Holtz, Greg Swain

Journal Articles

Use of carbon materials is no longer limited to diamond jewelry or graphite pencils and lubricants. The last decade has witnessed an explosion of technological applications driven by the development of fabrication methods and the discovery of several new classes of pure carbon. Structural diversity exhibited by the carbon atoms, from local chemical order to long-range crystalline order, is key to understanding their physical and chemical properties and in future materials development. This article summarizes the use of Raman spectroscopy as a principal tool to investigate the vibrational dynamics of carbon materials and to provide indirect structural characterization of their ...


Relationship Of Theoretical Patch Climatology To Polar Cap Patch Observations, M. D. Bowline, Jan Josef Sojka, R. W. Schunk Jan 1996

Relationship Of Theoretical Patch Climatology To Polar Cap Patch Observations, M. D. Bowline, Jan Josef Sojka, R. W. Schunk

All Physics Faculty Publications

During a southward orientation of the interplanetary magnetic field (IMF), patches are often observed moving antisunward across the polar cap. In saying “patches” we refer to structures in which the F region electron densities are enhanced relative to lower background levels; we do not in this paper consider patches which are observed optically (see J. J. Sojka et al., Ambiguity in identificiation of polar cap F region patches, submitted to the Journal of Atmospheric and Terrestrial Physics, 1995). The patches can be modeled by a process which involves the “chopping up” of the tongue of ionization (TOI) [Sojka et al ...


Scale-Invariant Phase Space And The Conformal Group, James Thomas Wheeler Jan 1996

Scale-Invariant Phase Space And The Conformal Group, James Thomas Wheeler

All Physics Faculty Publications

The gauge bundle of the 4-dim conformal group over an 8-dim base space, called biconformal space, is shown have a consistent interpretation as a scale-invariant phase space. Specifically, we show that a classical Hamiltonian system generates a differential geometry which is necessarily biconformal, and that the classical Hamiltonian dynamics of a point particle is equivalent to the specification of a 7-dim hypersurface in flat biconformal space together with the consequent necessary existence of a set of preferred curves. The result is centrally important for establishing the physical interpretation of conformal gauging.


Internal Time Formalism For Spacetimes With Two Killing Vectors, Joseph D. Romano, Charles G. Torre Jan 1996

Internal Time Formalism For Spacetimes With Two Killing Vectors, Joseph D. Romano, Charles G. Torre

All Physics Faculty Publications

The Hamiltonian structure of spacetimes with two commuting Killing vector fields is analyzed for the purpose of addressing the various problems of time that arise in canonical gravity. Two specific models are considered: (i) cylindrically symmetric spacetimes, and (ii) toroidally symmetric spacetimes, which respectively involve open and closed universe boundary conditions. For each model canonical variables which can be used to identify points of space and instants of time, {\it i.e.}, internally defined spacetime coordinates, are identified. To do this it is necessary to extend the usual ADM phase space by a finite number of degrees of freedom. Canonical ...


Resonance Lidar To Study Temperatures, Winds, And Metal Densities In The Upper Mesosphere And Lower Thermosphere, Vincent B. Wickwar, T D. Wilkerson, D Rees, S C. Collins Jan 1996

Resonance Lidar To Study Temperatures, Winds, And Metal Densities In The Upper Mesosphere And Lower Thermosphere, Vincent B. Wickwar, T D. Wilkerson, D Rees, S C. Collins

All Physics Faculty Publications

None available.


Multiple Polar Cap Arcs: Akebono (Exos D) Observations, T. Obara, T. Mukai, H. Hayakawa, K. Tsurda, A. Matsuoka, A. Nishida, H. Fukunishi, L. Zhu, Jan Josef Sojka, D. J. Crain Jan 1996

Multiple Polar Cap Arcs: Akebono (Exos D) Observations, T. Obara, T. Mukai, H. Hayakawa, K. Tsurda, A. Matsuoka, A. Nishida, H. Fukunishi, L. Zhu, Jan Josef Sojka, D. J. Crain

All Physics Faculty Publications

Akebono (Exos D) observations demonstrate that polar cap arcs sometimes have a fine structure, that is, multiple (double or triple) arcs with spacing of a few tens of kilometers. The multiple polar cap arcs are dominantly observed in the nightside polar cap region, suggesting that low background conductance favors the appearance of the structured arcs. A relationship between the spacing and the average energy of the precipitating electrons is investigated. Results show that a higher energy leads to a wider spacing. Akebono observations also show the existence of a downward current region embedded between upward current regions (arcs). Comparison of ...


Model-Observation Comparison Study Of Multiple Polar Cap Arcs, Lie Zhu, Cesar E. Valladares, Jan Josef Sojka, Robert W. Schunk, D. J. Crain Jan 1996

Model-Observation Comparison Study Of Multiple Polar Cap Arcs, Lie Zhu, Cesar E. Valladares, Jan Josef Sojka, Robert W. Schunk, D. J. Crain

All Physics Faculty Publications

A quantitative model-observation comparison of multiple polar cap arcs has been conducted by using a time-dependent theoretical model of polar cap arcs. In particular, the electrodynamical features of multiple polar cap arcs with various spacings are simulated and the results are compared with the images obtained from the All-Sky Intensified Photometer at Qaanaaq. The results show that the observed and simulated arcs are quite similar, both spatially and temporally. The results support the theory proposed by Zhu et al. [1993a, 1994b] that the structure of polar cap arcs is mainly determined by the magnetosphere-ionosphere (M-I) coupling processes and that the ...