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Proceedings Paper

Polarization measurements of the extreme ultraviolet (EUV) emission following excitation and ionization-excitation of helium by fast electron, proton, and molecular hydrogen (H2+ and H3+) impact
Author(s): Hocine Merabet; Reinhard F. Bruch; Stephan Fuelling; K. Bartschat; Alexander Godunov; James H. McGuire; A. N. Grum-Grzhimailo
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Paper Abstract

We report intensive experimental and theoretical data corresponding to helium extreme ultraviolet (EUV) emission in the 30-60 nm wavelengths range for e- + He, H+ + He, and Hn+ + He (n=2-3) collisions with impact velocities from 1.4 to 8.5 a.u. Specifically, the degree of linear polarization associated with HeI (1snp) 1Po levels, n=2-5, (λ=51.7 to 58.4 nm for n=2-5 to n=1 transitions) and HeII (2p) 2Po states (λ=30.4 nm) have been measured at intermediate- to high-energy range using a compact lightweight molybdenum/silicon multilayer mirror polarimeter (MLM). The combination of these polarization measurements with our previous total EUV cross sections has enabled us to determine experimental magnetic substate scattering angle-integrated cross sections σ0 and σ1for ML = 0, ±1, and 1 following excitation of He (1s2) 1S to HeI (1s2p) 1Po levels and ionization-excitation to He+ (2p) 2Po for electron and proton impact at a wide range velocities. The degree of linear polarization and obtained magnetic sublevel cross sections are compared to earlier theoretical calculations together with our recent 23-state R-Matrix, 1st and 2nd Born calculations. Such a detailed comparison may shed more light on the collision processes involved in positively and negatively single charge particle impact in helium. In particular it shows that electron-electron interactions play an important role in the ionization-excitation mechanism. In addition, this comprehensive database possibly will provide a deeper understanding of electron and proton induced jets in solar flare astrophysical investigations.

Paper Details

Date Published: 25 September 2002
PDF: 11 pages
Proc. SPIE 4819, Polarization Measurement, Analysis, and Applications V, (25 September 2002); doi: 10.1117/12.450401
Show Author Affiliations
Hocine Merabet, Univ. of Nevada/Reno (United States)
Reinhard F. Bruch, Univ. of Nevada/Reno (United States)
Stephan Fuelling, Univ. of Nevada/Reno (United States)
K. Bartschat, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Alexander Godunov, Tulane Univ. (United States)
James H. McGuire, Tulane Univ. (United States)
A. N. Grum-Grzhimailo, Drake Univ. (United States)

Published in SPIE Proceedings Vol. 4819:
Polarization Measurement, Analysis, and Applications V
Dennis H. Goldstein; David B. Chenault, Editor(s)

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