New Results for Double Excitation Processes with Helium Targets

Abstract

In this article we report on some new theoretical results on (e, 2e) excitation — ion-ization and (e,3e) of the ground state of helium. These results are a direct continuation of those presented in [1]. Our interest lies in the high energy regime and in geometries for which the incident and scattered electrons are very much faster than any ejected electron. Under these conditions, we may think of the collision as exciting a continuum state ψf of the isolated atom. In the case of excitation — ionization this state consists of the ejected electron, momentum K, moving in the field of an excited He⁺ ion, for example, the system He⁺(2s or 2p) + e^-(k). In (e,3e) we have a double continuum state of the atom. In the following, we use atomic units (au) in which ħ = m _e = e = 1.