Please use this identifier to cite or link to this item: http://repositorio.unicamp.br/jspui/handle/REPOSIP/1022
Type: Artigo de periódico
Title: Near threshold vibrational excitation of molecules by positron impact: A projection operator approach
Author: VARELLA, Marcio T. do N.
OLIVEIRA, Eliane M. de
LIMA, Marco A. P.
Abstract: We report vibrational excitation (v(i) = 0 -> v(f) = 1) cross-sections for positron scattering by H(2) and model calculations for the (v(i) = 0 -> v(f) = 1) excitation of the C-C symmetric stretch mode of C(2)H(2). The Feshbach projection operator formalism was employed to vibrationally resolve the fixed-nuclei phase shifts obtained with the Schwinger multichannel method. The near threshold behavior of H(2) and C(2)H(2) significantly differ in the sense that no low lying singularity (either virtual or bound state) was found for the former, while a e(+)-acetylene virtual state was found at the equilibrium geometry (this virtual state becomes a bound state upon stretching the molecule). For C(2)H(2), we also performed model calculations comparing excitation cross-sections arising from virtual (-i kappa(0)) and bound (+i kappa(0)) states symmetrically located around the origin of the complex momentum plane (i.e. having the same kappa(0)). The virtual state is seen to significantly couple to vibrations, and similar cross-sections were obtained for shallow bound and virtual states. (c) 2007 Elsevier B.V. All rights reserved.
Subject: positron scattering
vibrational excitation
Country: Holanda
Editor: ELSEVIER SCIENCE BV
Citation: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, v.266, n.3, p.435-440, 2008
Rights: fechado
Identifier DOI: 10.1016/j.nimb.2007.12.020
Address: http://dx.doi.org/10.1016/j.nimb.2007.12.020
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Date Issue: 2008
Appears in Collections:IFGW - Artigos e Materiais de Revistas Científicas

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