CORRELATION IN ION-ATOM COLLISIONS

Due to the strong electron-nucleus force in the target atom, many atomic collision processes are well-described within the independent particle model. This paper focuses on ion-atom collisions where dynamical correlations due to interaction between the electrons during the collision play an important role. Such correlations can be important for multi-electron transitions in weak coupling cases (high collision energies), since to first order in the projectile interaction and without correlation the cross section is zero. One example to be discussed is the double ionization of helium, where one manifestation of the correlation is the large difference in double ionization produced by protons and antiprotons. The situation for double ionization will be compared to other two electron processes, such as double excitation, excitation plus ionization, and transfer ionization.