Predissociation of the d 1Πg Rydberg state in O2: Nature of the Rydberg–valence interactions

Abstract

Predissociation of the higher vibrational states (v=4–8) of the d ¹Π_g Rydberg state is investigated experimentally using translational spectroscopy. These states predissociate to the O(¹D)+O(¹D) dissociation limit. Individual rotational levels of the v=4 state are observed for the first time, and the energies and rotational constants for both ¹⁶O₂ and ¹⁸O₂ isotopes are established. The observed predissociation behavior and natural linewidths are explained by invoking both Rydberg–valence and valence–valence interactions. The nearly diabatic nature of the 1 ¹Π_g and 2 ¹Π_g valence states is deduced from these observations. One of the‘‘diabatic’’ valence states is ‘‘bound,’’ and its perturbations on the v=1 to 3 of the Rydberg state explain observations reported from resonance enhanced multiphoton ionization experiments.