Laser predissociation spectroscopy of the f 4Πg state of O2+

Two quasibound vibrational levels of the f 4Πg state have been observed by monitoring O+ photofragments resulting from absorption of laser radiation by the a 4Πu state. The first spectroscopic constants for the f state have been derived from rotational and isotopic analyses. Measurements of the predissociation linewidths and photofragment kinetic energies have been used to refine estimates of the barrier in the f state potential curve and to identify likely predissociation mechanisms.