Ionisation to the projectile continuum by positron and electron collisions with neutral atoms

Abstract

It is pointed out that the singular structure in the differential cross section for electron ejection observed for heavy-ion impact ionisation should also be present for positron and electron impact ionisation. The structure occurs when the projectile and the ionised electron have low relative momentum in the final channel. For positrons the structure appears as a divergence, as for positive-ion impact. For electron impact a broad dip is predicted when both electrons emerge with nearly the same momentum.