The importance of projectile ionisation in studies of forward electron ejection from solid targets

Abstract

The velocity spectra of electrons ejected in the forward direction in ion-atom collisions with gas or solid targets are discussed in terms of charge exchange to the continuum (CEC) and of projectile ionisation. Measurements of the absolute cross sections for electron ejection during H 2 + (160–985 keV/amu) collisions with hydrogen gas show that projectile ionisation is the dominant source of ν e ≈ ν ion electrons over this energy range. The cusps observed show a width which is independent of projectile velocity unlike those for CEC. The significance of these results for collisions involving heavy ions and solid targets is discussed.