Selective population of spin-orbit levels in the autoionization of O2

Autoionization processes in O2 have been studied by measuring photoelectrons in the photon energy region between the O2+ X 2 Pi g and a 2 Pi u ionic states (12.4-15 eV). The present experimental results provide comprehensive information about autoionization dynamics since the decay routes from the spin-orbit components of the neutral autoionizing states to the two spin-orbit components of the ground ionic state are resolved. The intensity ratio of the O2+ X 2 Pi 1/2 and 2 Pi 3/2 components has been determined and strong Omega to Omega + selectivity has been observed. The observed selectivity is explained in terms of a model in which the orbital angular momentum along the internuclear axis of the positive ion core remains unchanged during the autoionization process. Using this model, Rydberg orbitals of the I, I' and I" autoionizing states are reassigned as 4s sigma g, 3d delta g and 3d sigma g, respectively, and the spin-orbit constant of the J state is determined.