Fine structure branching ratios of the O(3 P j ) atomic fragments from photodissociation of oxygen molecules at 157 and 193 nm

Direct photodissociation and predissociation of molecular oxygen from the B 3∑−u state have been studied by photoexcitation at 157 and 193 nm, respectively. The fine structure branching ratios and Doppler profiles of O(3Pj) photofragments were measured by a resonance-enhanced multiphoton ionization technique. The branching ratios of O(3Pj) j=2,1,0 are 0.74 ±0.03:0.21 ±0.02:0.042±0.004 for photodissociation at 157 nm and 0.47±0.05:0.31 ±0.04:0.22±0.44 at 193 nm. Both distributions are not statistical. The Doppler profiles of O(3Pj) from photodissociation of O2 at 157 nm are consistent with formation of O(1D)+O(3Pj).