Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session R1: Poster Session III
Wednesday, March 23, 2005
LACC Room: Exhibit Hall 1:00-4:00pm
Abstract ID: BAPS.2005.MAR.R1.55
Abstract: R1.00055 : Mean Excitation Energy for the Stopping Power of Silicon from Oscillator-Strength Spectra*
Preview Abstract Abstract
(Argonne National Laboratory)
(Saint Michael's College)
(Univ. of Vermont)
David Y. Smith
(Univ. of Vermont and Argonne National Laboratory)
The mean excitation energy, $I$, is the sole nontrivial property of matter appearing in Bethe's expression for the stopping power for a charged particle at high speed. When the dipole oscillator-strength spectrum, d$f$/d$E$, is fully known as a function of excitation energy, $E$, the $I$ value may be evaluated from ln($I)=\smallint $ ln($E)$ (d$f$/d$E)$ d$E$ / $\smallint $ (d$f$/d$E)$ d$E$. Following up work on metallic aluminum, we are analyzing experimental data for the dielectric response of crystalline silicon using Kramers-Kronig dispersion relations and sum rules. The experimental data include absorption, refraction, reflection, and EELS. For silicon, the best set of data in our current judgment gives $I$ = 163.5 $\pm $ 2 eV, where the uncertainty arises from using different but apparently equally reliable data and from numerical procedures. Our result is appreciably lower than the standard value, 173 $\pm $ 3 eV. It is noteworthy that our result for silicon is remarkably close to that for aluminum, both in the $I$ value and in the contributions to it from each electron shell (when scaled for electron occupation and shell-edge energy).
*Supported by US Department of Energy, Office of Science, Office of Nuclear Physics under contract W-31-109-Eng-38, and Materials Science Division under contract No. DE-FG02-02ER45964.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2005.MAR.R1.55
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