Origin of features in the energy spectra of electrons detached from fast H-in collisions with He and Ar atoms

Abstract

Using Born's approximation the authors have analysed the structure of the doubly differential cross section for electron loss from fast H- near the forward direction. They show that electrons ejected with velocities slightly smaller than the projectile, originate in collisions in which the 'diffuse' electron of H- scatters as a nearly-free electron and excites (ionises) the target. Electrons ejected with velocities close to that of the projectile come from three sources: (i) double-electron loss in which the final state is strongly influenced by the Coulomb interaction with the resulting fast proton; (ii) single electron loss in which the target is excited by the H core, while the ejected 'diffuse' electron acts as a separator; and (iii) single detachment with no excitation of the target which comprises a small fraction of the events for He targets, but becomes important for heavier targets such as Ar.