Two-electron processes in ion-atom collisions — experiment

Abstract

In an ion-atom collision, processes involving two electrons often compete with or contribute to the corresponding one-electron processes, making it important to isolate and identify these two-electron mechanisms in order to make detailed comparisons with theory. Four distinct two-electron processes occurring in single collisions are discussed, namely (a) two-electron capture, (b) two-electron loss from a projectile, (c) combined projectile electron loss and excitation, and (d) electron capture associated with additional target ionization. The importance of these two-electron processes compared to the relevant one-electron processes is considered, along with the question of whether independent-particle inte.ractions are dominant or whether electron-correlation effects must be taken into account in the description of these two-electron mechanisms.