Recent experimental studies of the spin dependence in electron-impact ionization of atomic hydrogen revealed the presence of deviations from the predictions of the conventional Wannier threshold theory of two-electron escape. We provide some insight into the possible origin of these deviations and reexamine the results of previous work that had claimed consistency with the Wannier theory but, with added statistical analysis, also seem to show deviations.

• Received 9 March 1992

DOI:https://doi.org/10.1103/PhysRevA.46.652