Abstract
Expressions for the double and triple differential cross sections for K-shell ionisation by relativistic electrons are derived with the plane wave impulse approximation (PWIA). Assuming the bound atomic electrons to be on-shell, the double differential cross section factorises in essence into the Moller cross section and the Compton profile. The triple differential off-shell cross section is given for Moller and Bhabba scattering. The results are compared with experimental data.