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Physics

Condensed matter

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Displaying 1101 - 1125 of 1237

Electron Inelastic Mean Free Paths in Solids at Low Energies

January 1, 1990
Author(s)
Shigeo Tanuma, Cedric J. Powell, David R. Penn
We have calculated electron inelastic mean free paths (IMFPs) for 50-200 eV electrons in 31 materials (27 elements and 4 compounds). These calculations extend those previously reported for 200-2000 eV electrons in the same materials but avoid an

Limitations on Electronic Mechanisms for High Temperature Superconducting Oxides

January 1, 1990
Author(s)
David R. Penn, Marvin Cohen, I Barbee
The effects of electronic mechanisms for electron pairing in high temperature superconducting oxides on both the transition temperature T c and the isotope effect parameter α are considered. It is shown that for the higher T c oxides, measured values of T

Material Dependence of Electron Inelastic Mean Free Paths at Low Energies

January 1, 1990
Author(s)
Shigeo Tanuma, Cedric J. Powell, David R. Penn
We have calculated electron inelastic mean free paths (IMFPs) for 50-2000 eV electrons in 31 materials (27 elements and 4 compounds). We present and discuss in this paper IMFP data for aluminum and gold in the 50-2000 ev Range. Substantial differences are

The Chemisorption of Chlorosilanes and Chlorine on Si(111)7*7

January 1, 1990
Author(s)
Lloyd J. Whitman, S Joyce, J Yarmoff, F McFeeley, L Terminello
The chemisorption of SiCl 4, Si 2Cl 6, and chlorine on Si(111)7x7 has been characterixed using soft X-ray photoemission with synchrotron radiation, thermal desorption spectroscopy, and Auger electron spectroscopy. SiCl 4 dissociatively chemisorbs on room

Theory of Spin Polarized Metastable Atom De-excitation Spectroscopy; Ni-He

January 1, 1990
Author(s)
David R. Penn, S Apell
Metastable spin-polarized He* atoms incident on a Ni surface undergo deexcitation in a process which yields electrons from the Ni. The number produced is observed to depend on the relative spin of the Ni and the He * atoms. The normalized difference in the

Weak versus Strong Coupling Theory for Bi 2 Sr 2 CaCu 2 O 8

January 1, 1990
Author(s)
Marvin Cohen, David R. Penn
The latest optical determination of the superconducting-gap function for Bi 2Sr 2CaCu 2O 8 is consistent with weak-coupling theory. In contrast, a large discontinuity in heat-capacity data suggests strong-coupling superconductivity, and appears to exceed

Electronic Correlations and Satellites in Superconducting Oxides

January 1, 1988
Author(s)
K Chang, Marvin Cohen, David R. Penn
The satellite observed at binding energy of 12-13 eV below the Fermi level in the high-T c oxide superconductors La 2-xSr xCuO 4 and YBa 2Cu 3O 7-δ is viewed as originating from a state with two holes bound at the same Cu site. As in the case of Ni metal

Free-electron-like Stoner Excitations in Fe

January 1, 1988
Author(s)
David R. Penn, S Apell
An analysis of spin-polarized electron-energy-loss experiments in Fe is described which (1) identifies the contribution of d-electron Stoner excitations, the usual type of Stoner excitation, (2) suggests that free-electron-like Stoner excitations are more

Electron Mean-Free-Path Calculations Using a Model Dielectric Function

January 1, 1987
Author(s)
David R. Penn
The inelastic electron mean free path as a function of energy is calculated for Cu, Ag, Au, and Al. The calculations are based on a model dielectric function ε(q,w), which is obtained from a modification of the statistical approximation. In this approach ε

Evidence for Free Electron-Like Stoner Excitation in Fe

January 1, 1987
Author(s)
David R. Penn
An analysis of spin-polarized electron-energy-loss experiments in Fe is described which suggests that (1) free-electron-like Stoner excitations are far more probable than the usual type and (2) exchange events involving relatively large energy losses are

Free Electron-Like Stoner Excitation in Fe

January 1, 1987
Author(s)
David R. Penn
Methods have recently developed to probe the Stoner excitation spectrum which has not been amenable to study by neutron diffraction. The experiments have utilized energy loss spectroscopy combined with spin polarization of the incident electron beam or

Scanning Tunneling Microscopy Applied to Optical Surfaces

January 1, 1986
Author(s)
Robert A. Dragoset, R Young, Howard P. Layer, S Mielczarek, E C. Teague, Robert Celotta
The technique of scanning tunneling microscopy has been applied to topographic mapping of two optical surfaces: a ruled grating replica and a diamond-turned gold mirror. We have demonstrated the ability of the scanning tunneling microscope to measure

Spin Polarized Secondary Electrons: Theory

January 1, 1986
Author(s)
David R. Penn, S Apell, S Girvin
We show that the spin polarization of the secondary electrons, P(E), yields useful information about the electron-electron interaction. The ration of majority to minority spin lifetimes is related to the measured values of P(E) by τ {uarr}(E)/τ {darr} (E =

Optical Properties of Small Metal Spheres: Surface Effects

April 25, 1983
Author(s)
David R. Penn, S Apell
It has been assumed that the optical properties of small spheres can be understood by means of a Drude dielectric function that incorporates a boundary scattering rate 1 / τ s~=v F / R, where vF is the Fermi velocity and R is the sphere radius. An

Anomalous Electron Energy Loss in Small Spheres

January 1, 1983
Author(s)
David R. Penn, S Apell
In analogy to the case of optical absorption, it is shown that inclusion of non-local surface effects results in a very large contribution to the energy loss of fast electrons scattered by a sphere. The scattering is found to be predominantly in the

The Diamond (111) Surface: A Dilemma Resolved

January 1, 1983
Author(s)
B B. Pate, B Waclawski, P M. Stefan, C Binns, T Ohta, M H. Hecht, P J. Jupiter, M L. Shek, Daniel T. Pierce, Nils Swanson, Robert Celotta, I. Lindau, W E. Spicer
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