THE MULTIPLET STATE DISTRIBUTION OF O(3PJ) PRODUCED IN THE PHOTODISSOCIATION OF O2 AT 157 NM

The fine structure population of O(P3) produced in the photodissociation of O2 at 157 nm was measured in a pump-and-probe experiment. The population of the ground state (J = 2) was found to be 93%, with only 6% in the J = 1 level and 1% in J = 0. The predominance of J = 2 is consistent with direct dissociation on the B3-SIGMA-u- potential energy surface. Based on available information in the literature we rule out excitation of the 3-PI-u state and curve crossing to the 5-PI-u state as possible origins of the population with J < 2. We infer that the populations of J < 2 is due to nonadiabatic transitions at large distances. Two mechanisms consistent with the data are a Demkov-type interaction, which is caused by coupling by the radial kinetic energy operator.