FORMATION AND DECAY OF (P-3(J))O ATOMS IN THE LASER FLASH-PHOTOLYSIS OF CHLORINE DIOXIDE (OCLO) AT 308NM

The primary quantum yields of O(P3J) and Cl(P2(3/2)) atoms in the laser flash photolysis of OClO(g) at 308 nm and 298 K and the kinetics of the subsequent oxygen atom decay have been investigated by time-resolved atomic resonance fluorescence measurements. The determined quantum yields are phi-O = 1.02 +/- 0.05 and phi-Cl < 0.01. Second-order rate constants for the reaction between O atoms and OClO are pressure dependent with a finite intercept. The rate constant for the bimolecular channel O + OClO --> O2 + ClO (1) has a value of k1 = (1.6 +/- 0.4) X 10(-13) cm3 molecule-1 s-1. Termolecular reaction rates for O + OClO + Ar --> ClO3 + Ar (2) can be fit with k20 = (1.4 +/- 0.3) X 10(-31) cm6 molecule-2 s-1 and k2infinity = (3.1 +/- 0.8) X 10(-11) cm3 molecule-1 s-1. A value of DELTA-H(f)(ClO3) = 55.6 +/- 4 kcal/mol is derived from k20 and unimolecular reaction theory by assuming a collision efficiency of beta = 0.76 for argon.