Triple and double differential cross sections for electron impact ionisation of helium for 'energy-sharing' kinematics

Abstract

The triple differential cross sections for electron impact ionisation of helium are investigated for 'energy-sharing' kinematics. A comparison is made with results of the simplified eikonal impulse approximation (EIA). Over the electron impact energy range from 200-2000 eV the authors also present absolute double differential cross sections for electron impact ionisation, in which only one existing electron is detected. It is shown that these cross sections are closely related to triple differential cross sections, in which two electrons are detected, for some scattering geometries. A model, which includes Rutherford scattering by the nucleus, is suggested, in order to explain the large discrepancy between the integrated EIA and the experimental data for very asymmetric energy disposition between the outgoing electrons.