Electron transitions in slow collisions of negative and positive atomic ions

Theoretical investigations of charge exchange and ionization processes accompanying collisions of negative and positive atomic ions are reviewed. Detailed analysis of the Coulomb Green function provides vast information about these processes. In particular, we took previously unknown sums of Coulomb wave function products over degenerate states. Adiabatic energies of the system and its wave functions can be expressed through these sums, whereas the wave functions turn out to possess very interesting and unexpected properties.