Collisional formation of heavy Rydberg ion-pair states

The formation of heavy Rydberg ion-pair states through electron transfer in collisions between K(np) Rydberg atoms and molecules that attach low-energy electrons is investigated. At low n, collisions with a wide variety of target species can lead to the formation of hound ion-pair states, a small fraction of which (under apropriate conditions) can subsequently dissociate as free ions through internal-to-translational energy transfer. The lifetimes of the ion-pair states can also be influenced by autodetachment of the electron or by neutralization through charge transfer. Two primary methods are employed to investigate the lifetimes of ion-pair states. Measurements of the onsets in the arrival time distribution of the ions provide lifetime information on short time scales (a few microseconds or less) for those ion pairs which undergo dissociation through conversion of internal energy. Additionally, ion pair behavior on longer time scales (> 1 --- 2 micros) can be studied as a function of binding energy through direct field dissociation