Energy shifts of binary-encounter electron peaks in ion-atom collisions

Abstract
The so-called binary-encounter electron peak resulting from collisions between quasifree target electrons and energetic projectile ions is studied. The shift in energy of the binary-encounter electron peak relative to the energy of scattered free electrons at rest is measured as a function of scattering angle in collisions between 1 and 1.5 MeV amu-1 Cq+ (q=4, 5 and 6) and H2 and He. The measured shifts are in good agreement with theoretical results based on the continuum distorted wave eikonal initial state approximation. Both theory and data show an increase of the shifts with projectile charge state and scattering angle. For observation angles larger than 30', the experimental shifts rise faster than theory.