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Proceedings Paper

Spectropolarimetric measurements of the extreme-ultraviolet emission from helium following e-, H+, H2+, and H3+ charged particle impact
Author(s): Hocine Merabet; Reinhard F. Bruch; Jonathan Hanni; Alexander Godunov; James H. McGuire; Igor Bray; D. V. Fursa; Klaus Bartchat; Hsiang-Chi Tseng; Chii-Dong Lin; Silvano Fineschi
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Paper Abstract

We present here comprehensive experimental data corresponding to helium extreme ultraviolet emission (EUV) for the 300-600A wavelength range in e- + He, H+ + He, and Hnn+ + He (n=2-3) collisions with impact velocities ranging from 1.4 to 6.9 a.u. The degree of linear polarization associated with HeI (1snp) 1Po -> (1s2) 1S decays for n-2-5 ((lambda) =510 to 584A) and HeII (2p) 2Po -> (1s) 2S transitions ((lambda) =304A), have been measured at intermediate and higher energies. These measurements have been conducted using a compact lightweight molybdenum/silicon multilayer mirror (MLM) spetropolarimeter. These experimental results are compared with our most advanced theoretical calculations using the close coupling method and several many body perturbation approaches. In this study, the degree of linear polarization will be discussed as a function of the projectile charge to elucidate few body excitation and ionization-excitation processes. Specifically, more sophisticated calculations including second Born approximation with full off-energy terms for the HeII (2p) 2Po sublevels have been used. The excellent agreement with our HeII Lyman-(alpha) data clearly demonstrates that off-energy terms in two-electron atomic interaction have very prominent effects. Our comprehensive experimental and theoretical database is also of great importance for the understanding of solar physics phenomena. Such results can be used as a new diagnostic tool for clarifying the role of electron and proton beams in solar flares.

Paper Details

Date Published: 10 December 2001
PDF: 10 pages
Proc. SPIE 4498, UV/EUV and Visible Space Instrumentation for Astronomy and Solar Physics, (10 December 2001); doi: 10.1117/12.450057
Show Author Affiliations
Hocine Merabet, Univ. of Nevada/Reno (United States)
Reinhard F. Bruch, Univ. of Nevada/Reno (United States)
Jonathan Hanni, Univ. of Nevada/Reno (United States)
Alexander Godunov, Tulane Univ. (United States)
James H. McGuire, Tulane Univ. (United States)
Igor Bray, Murdoch Univ. (Australia)
D. V. Fursa, Murdoch Univ. (Australia)
Klaus Bartchat, Drake Univ. (United States)
Hsiang-Chi Tseng, Chung Yuan Christian Univ. (Taiwan)
Chii-Dong Lin, Kansas State Univ. (United States)
Silvano Fineschi, Harvard-Smithsonian Ctr. for Astrophysics (Italy)

Published in SPIE Proceedings Vol. 4498:
UV/EUV and Visible Space Instrumentation for Astronomy and Solar Physics
Oswald H. W. Siegmund; Silvano Fineschi; Mark A. Gummin, Editor(s)

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