Recombination studies of Xe2+ following associative ionization of laser-excited Xe

Abstract

Experiments are described where two-photon transitions in atomic xenon have been laser-excited from the 1S0 ground state to Xe* np (n = 8−11) and Xe* nf (n = 4−8) Rydberg states in an apparatus which combines a time-of-flight mass spectrometer and a dispersive photoelectron spectrometer. Xe* atoms in nf-states, but not in np-states, undergo rapid associative ionization to form Xe2+, followed by dissociative recombination to form atoms predominantly in lower energy 6p and 5d excited states. Orbital selectivity for associative ionization can be explained by a simple qualitative model where the Rydberg nf-electron is radially localized outside the Xe+ core for long periods of time due to a larger centrifugal barrier in the effective atomic potential. This enhances the probability that excited Xe atoms in an nf state will encounter a ground state atom at those impact distances that lead to the formation of dimer ions.