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in subjects: "Energy Spectra"

open access

The Evolution of Ga and As Core Levels in the Formation of Fe/GaAs(001): A High Resolution Soft X-ray Photoelectron Spectroscopic Study

A high resolution soft x-ray photoelectron spectroscopic study of Ga and As 3d core levels has been conducted for Fe/GaAs (001) as a function of Fe thickness. This work has provided unambiguous evidence of substrate disrupting chemical reactions induced by the Fe overlayer--a quantitative analysis of the acquired spectra indicates significantly differing behavior of Ga and As during Fe growth, and our observations have been compared with existing theoretical models. Our results demonstrate that… more

Date: December 8, 2006

Creator: Thompson, J W; Neal, J R; Shen, T H; Morton, S A; Tobin, J G; Waddill, G D et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Nonconservative and reverse spectral transfer in Hasegawa-Mima turbulence

The dual cascade is generally represented as a conservative cascade of enstrophy to short wavelengths through an enstrophy similarity range and an inverse cascade of energy to long wavelengths through an energy similarity range. This picture, based on a proof due to Kraichnan [Phys. Fluids 10, 1417 (1967)], is found to be significantly modified for a spectra of finite extent. Dimensional arguments and direct measurement of spectral flow in Hasegawa-Mima turbulence indicate that for both the ene… more

Date: January 1, 1993

Creator: Terry, P. W. & Newman, D. E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

A three wavelength scheme to optimize hohlraum coupling on the National Ignition Facility

By using three tunable wavelengths on different cones of laser beams on the National Ignition Facility, numerical simulations show that the energy transfer between beams can be tuned to redistribute the energy within the cones of beams most prone to backscatter instabilities. These radiative hydrodynamics and laser-plasma interaction simulations have been tested against large scale hohlraum experiments with two tunable wavelengths, and reproduce the hohlraum energetics and symmetry. Using a thi… more

Date: December 16, 2010

Creator: Michel, P; Divol, L; Town, R & Rosen, M

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

THE TEMPERATURE-DEPENDENT SURFACE STRUCTURE, COMPOSITION AND ELECTRONIC PROPERTIES OF THE CLEAN SrTiO3(111) CRYSTAL FACE: LEED, AES, ELS AND UPS STUDIES

Low-energy-electron diffraction, Auger-electron spectroscopy, electron-energy-loss, and ultraviolet-photoelectron spectroscopies were used to study the structure, composition, and electron energy distribution of a clean single-crystal (111) face of strontium titanate (perovskite). The dependence of the surface chemical composition on the temperature has been observed along with corresponding changes in the surface electronic properties. High-temperature Ar-ion bombardment causes an irreversible… more

Date: December 1, 1977

Creator: Lo, Wei Jen & Somorjai, G. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Using Dynamic Quantum Clustering to Analyze Hierarchically Heterogeneous Samples on the Nanoscale

Dynamic Quantum Clustering (DQC) is an unsupervised, high visual data mining technique. DQC was tested as an analysis method for X-ray Absorption Near Edge Structure (XANES) data from the Transmission X-ray Microscopy (TXM) group. The TXM group images hierarchically heterogeneous materials with nanoscale resolution and large field of view. XANES data consists of energy spectra for each pixel of an image. It was determined that DQC successfully identifies structure in data of this type without p… more

Date: September 7, 2012

Creator: Hume, Allison & /SLAC, /Princeton U.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Chandra And HST Observations of Gamma-Ray Blazars: Comparing Jet Emission at Small And Large Scales

We present new Chandra and HST data for four gamma-ray blazars selected on the basis of radio morphology with the aim of revealing X-ray and optical emission from their jets at large scales. All the sources have been detected. Spectral Energy Distributions of the large scale jets are obtained as well as new X-ray spectra for the blazar cores. Modeling for each object the core (sub-pc scale) and large-scale ({approx}> 100 kpc) jet SEDs, we derive the properties of the same jet at the two scal… more

Date: March 20, 2007

Creator: Tavecchio, Fabrizio; Maraschi, L.; Wolter, A.; Cheung, C. C.; Sambruna, R. M. & Urry, C. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Variable VHE gamma-ray emission from Markarian 501

The blazar Markarian 501 (Mrk 501) was observed at energies above 100 GeV with the MAGIC telescope from May through July 2005. The high sensitivity of the instrument enabled the determination of the flux and spectrum of the source on a night-by-night basis. Throughout our observational campaign, the flux from Mrk 501 was found to vary by an order of magnitude, and to be correlated with spectral changes. Intra-night flux variability with flux-doubling times down to 2 minutes was also observed. T… more

Date: February 6, 2007

Creator: Albert, Jordi

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Abundances and Spectra for Cosmic-Ray Nuclei from Li to Fe For 2to 150 GeV/n

We report measurements of the absolute and relative abundances, differential energy spectra, and spectral indices for cosmic-ray nuclei from Li to Fe for 2 to 150 GeV/nucleon. These measurements were made using a balloon-borne superconducting magnetic spectrometer with scintillators and optical spark chambers. The abundances of Li, Be, and B for rigidities below 10 GV/c are consistent with an energy-independent mean interstellar pathlength of 4 1/2 {+-} 1/2 g cm{sup -2} for all propagation mode… more

Date: March 27, 1978

Creator: Orth, Chalres D.; Ruffington, Andrew; Smoot, George F. & Mast,Terry S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Radiation calculations for the ILC cryomodule

The MARS15 radiation simulations were performed for the ILC cryomodule. The model assumes a uniform beam loss intensity of 1 W/m of 750-MeV and 250-GeV electron along the inner surface of the beam pipe and the cavity iris of the 12-m cryomodule. Two-dimensional distributions of radiation dose in the module were obtained. Absorbed dose rate and energy spectra of electrons, photons, neutrons and protons were also obtained at the three cryogenic thermometers locations by filling with silicon mater… more

Date: April 1, 2007

Creator: Nakao, N.; Mokhov, N. V. & Klebaner, A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Nonlinear Dynamic Systems Response to Non-Stationary Excitation Using the Wavelet Transform: Final Report

The objective of this research project has been the development of techniques for estimating the power spectra of stochastic processes using wavelet transform, and the development of related techniques for determining the response of linear/nonlinear systems to excitations which are described via the wavelet transform. Both of the objectives have been achieved, and the research findings have been disseminated in papers in archival journals and technical conferences.

Date: January 15, 2006

Creator: Spanos, Pol D.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Quantum simulations of physics problems

If a large Quantum Computer (QC) existed today, what type of physical problems could we efficiently simulate on it that we could not efficiently simulate on a classical Turing machine? In this paper we argue that a QC could solve some relevant physical 'questions' more efficiently. The existence of one-to-one mappings between different algebras of observables or between different Hilbert spaces allow us to represent and imitate any physical system by any other one (e.g., a bosonic system by a s… more

Date: January 1, 2003

Creator: Somma, R. D. (Rolando D.); Ortiz, G. (Gerardo); Knill, E. H. (Emanuel H.) & Gubernatis, J. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Solutions of the scalar Helmholtz equation in the elliptic cylinder coordinate system

A method for determining the eigenvalues for the scalar Helmholtz equation in the elliptic cylinder coordinate system is described. Complex expansion parameters are considered so that numerical results for physical problems involving energy dissipation as well as energy flow can be obtained. Sample numerical results are presented for the eigenvalues, radial eigenfunctions, and angle eigenfunctions. Applications of these results are discussed. (auth)

Date: October 15, 1973

Creator: Lytle, R.J. & Lager, D.L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

New Benchmarks from Tokamak Experiments for Theoretical Calculations of the Dielectronic Satellite Spectra of Helium-like Ions

Dielectronic satellite spectra of helium-like argon, recorded with a high-resolution X-ray crystal spectrometer at the National Spherical Torus Experiment, were found to be inconsistent with existing predictions resulting in unacceptable values for the power balance and suggesting the unlikely existence of non-Maxwellian electron energy distributions. These problems were resolved with calculations from a new atomic code. It is now possible to perform reliable electron temperature measurements a… more

Date: August 29, 2003

Creator: Bitter, M.; Gu, M.F.; Vainshtein, L.A.; Beiersdorfer, P.; Bertschinger, G.; Marchuk, O. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

The Evolution of Early-type Field Galaxies Selected from a NICMOS Map of the Hubble Deep Field North

The redshift distribution of well-defined samples of distant early-type galaxies offers a means to test the predictions of monolithic and hierarchical galaxy formation scenarios. NICMOS maps of the entire Hubble Deep Field North in the F110W and F160W filters, when combined with the available WFPC2 data, allow us to calculate photometric redshifts and determine the morphological appearance of galaxies at rest-frame optical wavelengths out to z {approx} 2.5. Here we report results for two subsam… more

Date: March 3, 2004

Creator: Somerville, R,; Stanford, S. A.; Budavari, T. & Conselice, C. J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A Distributed Activation Energy Model of Thermodynamically Inhibited Nucleation and Growth Reactions and its Application to the beta-delta Phase Transition of HMX

Detailed and global models are presented for thermodynamically inhibited nucleation-growth reactions and applied to the {beta}-{delta} Phase Transition of HMX (nitramine octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine). The detailed model contains separate kinetic parameters for the nucleation process, including an activation energy distribution resulting from a distribution of defect energies, and for movement of the resulting reaction interface within a single particle. A thermodynamic inhib… more

Date: June 18, 2004

Creator: Burnham, A K; Weese, R K & Weeks, B L

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Gamma Spectra Resulting From the Annihilation of Positrons with Electrons in Single, Selected Core Levels of Cu, Ag and Au

The {gamma}-ray energy spectra due to positron annihilation with the 3p core-level of Cu, the 4p core-level of Ag, and 5p core level of Au were obtained separately from the total annihilation spectrum by measuring the energies of {gamma}-rays time coincident with Auger electrons emitted as a result of filling the core-hole left by annihilation. The results of these measurements are compared to the total annihilation spectra and with LDA based theoretical calculations. A comparison of area norma… more

Date: July 25, 2005

Creator: Kim, S.; Eshed, A.; Goktepeli, S.; Sterne, P. A.; Koymen, A. R.; Chen, W. C. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Beam interaction measurements with a Retarding Field Analyzer

A Retarding Field Analyzer (RFA) was designed and inserted in a drift region of a magnetic transport section of the High Current Experiment (HCX). It measures ions or electrons resulting from the beam interaction with the background gas and walls. The ions are expelled during the beam by the space-charge beam potential, and the electrons are expelled mainly at the end of the beam, when the beam potential decays. The measured electrons have a Maxwellian energy distribution and the measured ions … more

Date: March 28, 2006

Creator: Covo, M K; Molvik, A W; Friedman, A; Barnard, J J; Seidl, P; Logan, B G et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

DT results of TFTR`s alpha collector

An escaping alpha collector probe has been developed for TFTR`s DT phase to complement the results of the lost alpha scintillator detectors which have been operating on TFTR since 1988. Measurements of the energy distribution of escaping alphas have been made by measuring the range of alphas implanted into nickel foils located within the alpha collector. Exposed samples have been analyzed for 4 DT plasma discharges at plasma currents of 1.0 and 1.8 MA. The results at 1.0 MA are in good agreemen… more

Date: November 1, 1996

Creator: Herrmann, H. W.; Zweben, S. J.; Darrow, D. S.; Timberlake, J. R.; Chong, G. P.; Haasz, A. A. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Preliminary Observation of Nonlinear Effects in Compton Scattering

In a new experiment at the Final Focus Test Beam at SLAC a low- emittance 46.6 GeV electron beam is brought into collision with terawatt pulses from a 1.06 {mu} wavelength Nd:glass laser. Peak laser intensities of 10{sup 18} W/cm{sup 2} have been achieved corresponding to a value of 0.6 for the parameter {eta} = {ital eE/mw{sub 0}c}, and to a value of 0.3 for the parameter {Upsilon} = {ital E{sup *}/E{sub crit}} = 2{gamma}{ital ehE}/{ital m}{sup 2}{ital c}{sup 3} in the case of frequency double… more

Date: July 20, 1996

Creator: Bula, Christian; McDonald, K. T.; Prebys, E. J.; Bamber, C.; Boege, S.; Kotseroglou, T. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Observation of sawtooth redistribution of nonthermal, confined alpha particles in TFTR D-T discharges

Radial profiles of the density of confined alpha particles with energies in the 0.15-0.6 MeV range are spectroscopically observed before and after a sawtooth crash in a TFTR D-T plasma. A large drop in the core alpha density is seen indicating expulsion of alphas from the core to the plasma periphery. The measured changes in the alpha density profiles are consistent with predictions based on the Kolesnichenko sawtooth model, indicating that it may be used to reliably predict the effect of sawte… more

Date: May 1, 1996

Creator: Stratton, B.; Budny, R.; Chang, Z.; Fonck, R.; Wising, F. & Odblom, A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Ortho- and para-hydrogen in neutron thermalization

The large difference in neutron scattering cross-section at low neutron energies between ortho- and para-hydrogen was recognized early on. In view of this difference (more than an order of magnitude), one might legitimately ask whether the ortho/para ratio has a significant effect on the neutron thermalization properties of a cold hydrogen moderator. Several experiments performed in the 60`s and early 70`s with a variety of source and (liquid hydrogen) moderator configurations attempted to inve… more

Date: September 1998

Creator: Daemen, L. L. & Brun, T. O.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Charged Particle Spectroscopy on Omega (Final report)

Using the 2-MeV Van de Graaf Accelerator at SUNY Geneseo's Nuclear Structure Laboratory, a {sup 3}He-implanted tantalum target was bombarded by 450-keV deuterons to produce high energy protons via the {sup 3}He(d,p){sup 4}He reaction. A 1500-{micro}m surface barrier detector with a 3/16 inch diameter collimator was placed at 8.75 cm from the target and 135{sup o} from the incident beam. A movable arm was setup so that an array of aluminum filters of varying thicknesses could be rotated in front… more

Date: January 1, 2001

Creator: Fletcher, K.; Padalino, S.; Schwartz, B.; Olsen, M.; Wakeman, T. & Petrasso, R.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Model Etch Profiles for Ion Energy Distribution Functions in an Inductively Coupled Plasma Reactor

Rectangular trench profiles are modeled with analytic etch rates determined from measured ion distribution functions. The pattern transfer step for this plasma etch is for trilayer lithography. Argon and chlorine angular ion energy distribution functions measured by a spherical collector ring analyzer are fit to a sum of drifting Maxwellian velocity distribution functions with anisotropic temperatures. The fit of the model ion distribution functions by a simulated annealing optimization procedu… more

Date: December 14, 1998

Creator: Abraham-Shrauner, B.; Chen, W. & Woodworth, J.R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Electromagnetic Structure of Few-Nucleon Systems: a Critical Review

Our current understanding of the structure of nuclei with up to A=8, including energy spectra, electromagnetic form factors, and capture reactions, is critically reviewed within the context of a realistic approach to nuclear dynamics based on two- and three-nucleon interactions and associated electromagnetic currents.

Date: October 1, 2000

Creator: Schiavilla, R.

Item Type: Article

Partner: UNT Libraries Government Documents Department