(e,2e) and (e,3-1e) studies on double processes of He near the Bethe ridge

Abstract

We report (e,2e) and (e,3‐1e) experiments on the double processes of He, i.e. single ionization with simultaneous excitation and double‐ionization. The symmetric noncoplanar geometry combined with high incident electron energies has made it possible to study at large momentum transfers. The results are compared with plane wave impulse approximation (PWIA) calculations using He wavefunctions of various levels of sophistication. It is shown that shapes of the momentum dependent (e,2e) and (e,3‐1e) cross sections are well reproduced by the PWIA calculations when highly correlated wavefunctions are employed, but noticeable discrepancies between experiment and theory remain in magnitude. The discrepancies are, however, reduced with increasing impact energies, suggesting higher excitation energies may be required to analyze these double processes in terms of the PWIA.