Excitation and deexcitation processes in slow collisions of Rydberg atoms with ground-state parent atoms

The excitation and deexcitation processes in slow collisions of highly excited (Rydberg) atoms with ground-state parent atoms are considered. A mechanism, based on the quasiresonant energy transfer within the electronic part of the colliding system, is proposed for these processes. Both direct and exchange reaction channels are included into the treatment. Expressions for the n→n^' transition probabilities are obtained in closed form. Probability and cross section calculations for some transitions and level decays in the H*(n)-H system are presented.