Out-of-plane (e, 2e) experiments on helium L=0, 1, 2 autoionizing levels.

ABSTRACT

Out-of-plane (e, 2e) measurements are reported for the helium autoionizing levels (2s2)1S, (2p2)1D, (2s2p)1P, and for direct ionization. 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.