Competition between autoionization and dissociation in the[O2+(B 2Σg−)]nl and[O2+(c 4Σu−)]nl Rydberg states investigated by photon-induced dissociation to neutral fragments

Abstract

Formation of fluorescing and metastable fragments from photon-induced dissociation ofO2 has been investigated in the 20.2–21.2 eV and 22.5–25.0 eV photon energy regions underhigh resolution. The neutral particles are detected using a microchannel plate stack, whereelectric potentials prevent charged particles from reaching the detector. Yieldcurves of excited neutral particles exhibit peaks at Rydberg states converging toO2+(B 2Σg−) andO2+(c 4Σu−).Furthermore, these yields are strongly enhanced athigh-n,enabling the measurement of their energy location and width. Asimple model for the decay of the Rydberg states converging toO2+(c 4Σu−) based on the competition between autoionization and neutral dissociation is used todescribe qualitatively the observed spectrum. The results indicate that the lifetime of theO2+(c 4Σu−)v = 0 level is two orders of magnitude longer than that of theO2+(c 4Σu−)v = 1 level.