Out-of-plane (e,2e) angular distributions and energy spectra of helium L = 0,1,2 autoionizing levels
- Physics Department, Illinois Wesleyan University, P.O. Box 2900, Bloomington, Illinois 61702-2900 (United States)
- Department of Physics and Astronomy, Drake University, Des Moines, Iowa 50311 (United States)
- Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506-0055 (United States)
Angular distribution and spectral (e,2e) measurements are reported for the helium autoionizing levels (2s{sup 2}){sup 1}S, (2p{sup 2}){sup 1}D, and (2s2p){sup 1}P. A special out-of-plane geometry is used where the ejected electrons are emitted in a plane perpendicular to the scattered electron direction. The kinematics are chosen so that this plane contains the momentum-transfer direction. While the recoil peak almost vanishes in the angular distribution for direct ionization, it remains significant for the autoionizing levels and exhibits a characteristic shape for each orbital angular momentum L=0,1,2. A second-order model in the projectile-target interaction correctly reproduces the observed magnitudes of the recoil peaks, but is a factor of 2 too large in the central out-of-plane region. Observed (e,2e) energy spectra for the three resonances over the full angular range are well reproduced by the second-order calculation. Calculations using a first-order model fail to reproduce both the magnitudes of the recoil peaks and the spectral line profiles.
- OSTI ID:
- 21528886
- Journal Information:
- Physical Review. A, Vol. 82, Issue 6; Other Information: DOI: 10.1103/PhysRevA.82.062705; (c) 2010 American Institute of Physics; ISSN 1050-2947
- Country of Publication:
- United States
- Language:
- English
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