Non-adiabatic ionization of hydrogen atoms by highly charged ions

Based on the concepts of the classical barrier model and the analytical properties of the potential energy curves of the one-electron diatomic molecular ion, a direct physical description of slow ionizing collisions between highly charged ions and atoms is given. New expressions for the energies of the quasi-stationary states localized on the top of the potential barriers are used to derive simple expressions for the ionization cross sections in the limit of high charge states. A simple scaling in reduced variables is possible for the low energy ionization cross section in this limit.