Neutral fragmentation of superexcited oxygen molecules

The mechanisms of neutral dissociation of oxygen molecules in the excitation energy range 15–25 eV have been studied in a dispersed fluorescence experiment. By detecting the fluorescence from excited oxygen atoms, we find that neutral superexcited O₂ states below 20 eV dissociate into O(g.s.)+O(3s,3p). At higher excitation energies (hν=20–25eV) the curve-crossing interactions following excitations to members of the Rydberg c⁴Σ_u^- series also yield atoms in Rydberg states (nl,n>~4). The experimental data are analyzed on the ground of many-body perturbation theory, calculations which indicate the structure of the predissociating states converging to the experimentally observed ones.