PREDISSOCIATION DYNAMICS OF THE O2B (3)SIGMA(-)(U) STATE - VIBRATIONAL-STATE DEPENDENCE OF THE PRODUCT FINE-STRUCTURE DISTRIBUTION

The predissociation of the O2B (3) Sigma(u)(-) state (v=0-11) is inves tigated using fast beam photofragment translational spectroscopy. The energy resolution of the experiment, 7-10 meV, is sufficient to yield the correlated fine structure distribution P(j(1),j(2)) for the two O( P-3(j)) fragments. These spin-orbit branching ratios depend markedly o n the vibrational quantum number, providing detailed insight into a re latively unexplored facet of molecular dissociation dynamics. No less than four repulsive states are expected to mediate the predissociation of the B (3) Sigma(u)(-) state, primarily via spin-orbit coupling, an d the couplings among these states at long range (R similar to 5-7 Ang strom) determine the final spin-orbit distributions P(j(1),j(2)) We ha ve attempted to model these distributions in both the adiabatic and di abatic limits, with neither limit proving very successful. A more phen omenological approach to fitting our data suggests that products with j(1) = j(2) = 2 result from single transitions between adiabatic poten tials at long range, whereas the populations in the other product stat es are determined by multiple transitions among the repulsive states. (C) 1995 American institute of Physics.