Triple and double differential cross sections for electron impact ionisation of helium and molecular hydrogen

Abstract

The triple (and double) differential cross sections for electron impact ionisation of helium and molecular hydrogen are investigated to a much higher accuracy than obtained before. In a coplanar symmetric geometry ( theta =45 degrees ) both electrons emerging from the ionisation event-with equal velocities- are detected in coincidence. Over the impact energy range from 200 to 2800 eV the authors present absolute triple (double) differential cross sections containing an experimental error smaller than 20(10)%. A detailed comparison is made with results from various theoretical approaches.