Out-of-plane (e,2e) angular distributions and energy spectra of helium L = 0,1,2 autoionizing levels

B. A. Deharak, K. Bartschat, N. L.S. Martin

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


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 languageEnglish
Article number062705
JournalPhysical Review A - Atomic, Molecular, and Optical Physics
Issue number6
StatePublished - Dec 8 2010

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics


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