Abstract
Angular distribution and spectral (e,2e) measurements are reported for the helium autoionizing levels (2s2)1S, (2p2)1D, and (2s2p)1P. 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.
Original language | English |
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Article number | 062705 |
Journal | Physical Review A - Atomic, Molecular, and Optical Physics |
Volume | 82 |
Issue number | 6 |
DOIs | |
State | Published - Dec 8 2010 |
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics