Forward electron emission in Cq+-He collisions.

Abstract

Differential cross sections are presented for 15[degree] and 20[degree] electron emission in 100- and 150-keV/u C[sup [ital q]+]-He collisions where the projectile charge states are 0 to 4+. Coincidences between electrons emitted at 20[degree] and projectiles which captured or lost electrons in the collisions were also measured. The coincidence and noncoincidence data are used to demonstrate how partial screening of the projectile nuclear charge and direct interactions between projectile and target electrons influence the electron emission. In addition, the relative importance of multielectron transitions associated with either electron capture or electron loss by the projectile is demonstrated. Finally, the data are used to test whether saddle-point ionization is important in these ionizing collisions, as has recently been suggested. The present data do not support this suggestion and are in disagreement with the measurements which do support it. Furthermore, it is demonstrated that dressed ion impact data are inappropriate for testing for a saddle-point ionization mechanism.