Physics Commons^™

Nanoscale Oxide Patterns On Si (100) Surfaces, T. -C. Shen, C. Wang, J. W. Lyding, J. R. Tucker

T. -C. Shen

Ultrathin oxide patterns of a linewidth of 50 Å have been created on Si(100)‐2×1 surfaces by a scanning tunneling microscope operating in ultrahigh vacuum. The oxide thickness is estimated to be 4–10 Å. The morphology and spectroscopy of the oxide region are obtained. Hydrogen passivation is used as an oxidation mask. The defects caused by oxidation in the passivated region before and after the hydrogen desorption are compared and discussed. The multistep silicon processings by an ultrahigh vacuum scanning tunneling micropscope is thus demonstrated.

Correlations Between Auditory‐Filter Shape Parameters Measured At Proximal Center Frequencies, Marc A. Fagelson, Craig A. Champlin

Marc A. Fagelson

Pion Fusion In Peripheral Pp Collisions, Alec Schramm, Burndt Muller

Alec J Schramm

We estimate the cross section for quasielastic double pion exchange in high energy proton-proton collisions. Total and elastic ππ cross sections are calculated in an equivalent pion approximation, with pion-baryon vertices taken from chiral perturbation theory.

Trajectory Mapping And Applications To Data From The Upper Atmosphere Research Satellite, Gary A. Morris, Mark R. Schoeberl, Lynn C. Sparling, Paul A. Newman, Leslie R. Lait, Lee Elson, Joe Waters, Robert A. Suttie, Aidan Roche, Jack Kumer, James M. Russell Iii

Gary A. Morris

The problem of creating synoptic maps from asynoptically gathered trace gas data has prompted the development of a number of schemes. Most notable among these schemes are the Kalman filter, the Salby-Fourier technique, and constituent reconstruction. This paper explores a new technique called "trajectory mapping." Trajectory mapping creates synoptic maps from asynoptically gathered data by advecting measurements backward or forward in time using analyzed wind fields. A significant portion of this work is devoted to an analysis of errors in synoptic trajectory maps associated with the calculation of individual parcel trajectories. In particular, we have considered (1) calculational errors; (2) …

Origin Of The 〈11/20〉 Atomic Short-Range Order In Au-Rich Au-Fe Alloys, M. F. Ling, J. B. Staunton, Duane D. Johnson, F. J. Pinski

Duane D. Johnson

We have calculated the atomic short-range order (ASRO) and paramagnetic susceptibility in high-temperature, chemically disordered Au75Fe25 and Au90Fe10, using a density-functional-based, electronic-structure method. For both alloys, we obtain 〈11/20〉-type ASRO, in excellent agreement with experiments performed on samples that have been fast quenched from high temperature. We also identify the underlying electronic mechanism responsible for this unusual ordering behavior. During annealing at high temperatures, we suggest that aligning local moments via an external magnetic field will produce interesting AuFe alloys with 〈100〉-type ASRO.

High-Resolution Ultraviolet Spectroscopy Of Jupiter's Aurora With The Hubble Space Telescope, Y. H. Kim, John J. Caldwell, Jane L. Fox

Jane L. Fox

In 1993 June and July, we obtained 18 spectra of Jupiter's aurora in the wavelength range 1586-1620 Å using the Goddard High Resolution Spectrograph on board the Hubble Space Telescope (HST). The field of view for each observation was 2" × 2". There were 14 spectra of the northern and four spectra of the southern auroral ovals. The spectra are dominated by vibrational-rotational lines of the H₂ Lyman band system, from which we have determined H₂ rotational temperatures which correspond to the altitude region where most of the auroral emission originates. Intense emission was observed in …

A Unified Topological Approach To Electromagnetic Environmental Effects Protection, George H. Baker, J. Philip Castillo, Edward F. Vance

George H Baker

The presentation recommends an approach for unifying electronic system protection designs for a wide spectrum of electromagnetic environments. A general electromagnetic topological construct is developed as the basis for a consistent shielding and terminal protection methodology. Spectral characteristics of multiple interfering electromagnetic sources, both internal and external, are described. Effects addressed include EMI/EMC, lightning, nuclear EMP, and RF weapons. Protection practices for individual effects are discussed and means for integrating these into a single protection topology.

Nanosubharmonics: The Dynamics Of Small Nonlinear Contacts, Nancy Burnham, A Kulik, G Gremaud, Gad Briggs

Nancy A. Burnham

We observed the generation of subharmonics and chaos in a nanometer-sized mechanical contact. To first order, the behavior matches that of macroscopic systems, with some intriguing secondary differences. As the occurrence of periodic behavior (subharmonics) is related to the coefficient of restitution, it may be possible to image local energy dissipation with nanometer resolution.

Electron Scattering From 10b, A Cichocki, J Dubach, R S. Hicks, Gerald Alvin Peterson

Gerald Alvin Peterson

Electron scattering measurements have been made in order to determine the longitudinal and transverse form factors of low-lying level in 10B. With the exception of the broad 5.18 MeV level, results were obtained for all known levels up to 6.7 MeV. The measurements span the momentum transfer range q=0.48–2.58 fm-1. The primary objective of this work was to improve the data on the pure isovector M3 form factor of the 1.740 MeV excitation, the transform of which yields the 1p3/2 single-nucleon wave function. A Woods-Saxon potential was found to provide a much better representation of the data than the harmonic …

Fourier Series And Optical Transform Techniques In Contemporary Optics: An Introduction, Raymond Wilson, Sean Mccreary

Raymond Wilson

Van Hove Singularity Induced L11 Ordering In Cupt, J. F. Clark, F. J. Pinski, Duane D. Johnson, P. A. Sterne, J. B. Staunton, B. Ginatempo

Duane D. Johnson

We describe an ordering mechanism that arises due to coupling between electronic states at van Hove singularities. This novel mechanism, which naturally leads to ordered structures with small unit cells, couples states near the Fermi energy which are localized at high-symmetry points in k space, in contrast to the conventional mechanism which relies on large parallel sheets of Fermi surface. Using first-principles calculations of the electronic structure of ordered and disordered alloys, we show that this mechanism drives the unusual short- and long-range order found in fcc CuPt.

Time Dependent Response Of Equatorial Ionospheric Electric Fieldsto Magnetospheric Disturbances, Bela G. Fejer, L. Scherliess

Bela G. Fejer

We use extensive radar measurements of F region vertical plasma drifts and auroral electrojet indices to determine the storm time dependence of equatorial zonal electric fields. These disturbance drifts result from the prompt penetration of high latitude electric fields and from the dynamo action of storm time winds which produce largest perturbations a few hours after the onset of magnetic activity. The signatures of the equatorial disturbance electric fields change significantly depending on the relative contributions of these two components. The prompt electric field responses, with lifetimes of about one hour, are in excellent agreement with results from global convection …

Statistical Properties Of Schriidinger Real And Imaginary Cat States, Victor V. Dodonov, Serguei Y. Kalmykov, Vladimir I. Man'ko

Serge Youri Kalmykov

We study the photon statistics in the superpositions of coherent states |\alpha> and |\alpha*> named “Schroedinger real and imaginary cat states”. The oscillatory character of the photon distribution function (PDF) emerging due to the quantum interference between the two components is shown, and quadrature squeezing is observed for moderate values |\alpha| ~ 1. In spite of the quantity <\delta n^2> / tending to unity (like in the Poissonian PDF) at |\alpha| >> 1, the photon statistics is essentially non-Poissonian for all values of |\alpha|. The factorial moments and cumulants of the PDF are calculated, and oscillations of their ratio are demonstrated.

Alpha+28si Cluster Structure As Solitons On The Nuclear Surface, Andrei Ludu

Andrei Ludu

No abstract provided.

Quasimolecular Resonances In Alpha+20ne Systems, Andrei Ludu

Andrei Ludu

No abstract provided.

Vortex Dynamics In Single Crystal Yba2cu3o7 Probed By 63cu Nuclear Spin Echo Measurements In The Presence Of Transport Current Pulses, Charles Recchia, C Pennington, H Haughlin, G Lafyatis

Charles H Recchia

No abstract provided.

Local Non-Equilibrium Model For Rapid Solidification Of Undercooled Melts, Sergey Sobolev

Sergey Sobolev

No abstract provided.

Two Temperature Stefan Problem, Sergey Sobolev

Sergey Sobolev

No abstract provided.

Applications Of Extended Thermodynamics ...Part I., Sergey Sobolev

Sergey Sobolev

No abstract provided.

Applications Of Extended Thermodynamics ...Part Ii., Sergey Sobolev

Sergey Sobolev

No abstract provided.

Commensurate And Incommensurate Ordering Tendencies In The Ternary Fcc Cu-Ni-Zn System, J. D. Althoff, Duane D. Johnson, F. J. Pinski

Duane D. Johnson

We show that Fermi-surface (FS) nesting drives both the incommensurate and commensurate ordering tendencies of the fcc ternary Cu-Ni-Zn system. Surprisingly, commensurate order persists over a wide range of composition, despite its origins. For Cu2NiZn, we discuss how FS nesting and the other effects of alloying lead to ordering tendencies consistent with the experimentally observed order-disorder transformations. All calculations are based on a first-principles theory of the atomic short-range order in alloys with an arbitrary number of components.

Global Equatorial Ionosphericvertical Plasma Drifts Measured By The Ae-E Satellite, Bela G. Fejer, E. R. De Paula, R. A. Heelis, W. B. Hanson

Bela G. Fejer

Ion drift meter observations from the Atmosphere Explorer E satellite during the period of January 1977 to December 1979 are used to study the dependence of equatorial (dip latitudes ≤ 7.5°) F region vertical plasma drifts (east-west electric fields) on solar activity, season, and longitude. The satellite-observed ion drifts show large day-to-day and seasonal variations. Solar cycle effects are most pronounced near the dusk sector with a large increase of the prereversal velocity enhancement from solar minimum to maximum. The diurnal, seasonal, and solar cycle dependence of the longitudinally averaged drifts are consistent with results from the Jicamarca radar except …

Absolute Integrated Cross Sections For Some O2 Herzberg I Transitions Near 248–249 Nm, Zhen-Chuan Bao, Edward Yu, John R. Baker

Edward Yu

A frequency doubled tunable dye laser system with ∼0.4 cm−1 resolution was used to measure the integrated absorption cross sections of more than 20 rotational transitions in the O2 Herzberg I (A  3Σ+ u ←X  3Σ− g ) 8‐0 and 9‐0 vibrational bands near 248 nm and 249 nm. Oxygen pressures from 200 to 800 Torr and path lengths from 5 to 25 m were employed. The measured absorbances were fitted using a nonlinear least squares analysis and Beer’s Law to obtain absolute values for the individual transition integrated cross sections in good agreement with a recent spectral simulation and …

Comment On 'Simulation Of A Two-Dimensional Rayleigh-Bénard System Using The Direct Simulation Monte Carlo Method, Alejandro Garcia, F. Baras, M. Malek Mansour

Alejandro Garcia

No abstract provided.

A Consistent Boltzmann Algorithm, Alejandro Garcia, F. Alexander, B. Alder

Alejandro Garcia

The direct simulation Monte Carlo method for the Boltzmann equation is modified by an additional displacement in the advection process and an enhanced collision rate in order to obtain the exact hard sphere equation of state at all densities. This leads to consistent thermodynamic and transport properties in the low density (Boltzmann) regime. At higher densities transport properties are comparable to the predictions of the Enskog model. The algorithm is faster than molecular dynamics at low and moderate densities and readily run on a parallel architecture

A Thermodynamic Model For Pressurized Solids, Miron Kaufman, Herbert Schlosser

Miron Kaufman

A thermodynamic model for solids under pressure is developed by assuming the universal equation of state and that under zero pressure the free energy is equal to the harmonic crystal (Debye) free energy. The model is applied to gold. In the case of nanocrystals this model reproduces the observed enhancement of the isobaric heat capacity and of the thermal expansion. Our model calculations are free of the ambiguities and inconsistencies connected with the Gruneisen equation, which was used in previous theoretical work.

Quark Masses And Binding-Energy In A Proton - Answer To Question Number-2a, Br Holstein

Barry R Holstein

No abstract provided.

Determination Of Plasma Parameters In A Dc Arcjet Part Ii, Scott Reeve, Wayne Weimer

Scott Reeve

No abstract provided.