Photodissociation of ClONO2: 2. Time-Resolved Absorption Studies of Product Quantum Yields

The quantum yield for NO 3 production in the UV photolysis of ClONO 2 was measured via transient 661.9 nm absorption of NO 3 following pulsed laser photolysis and was found to be 0.93 ± 0.24 at 352.5 nm, 0.67 ± 0.09 at 308.15 nm, 0.60 ± 0.09 at 248.25 nm, and 0.18 ± 0.04 at 193 nm. The Cl atom quantum yield was measured by reacting Cl with ClONO 2 to produce NO 3 through the reaction Cl + ClONO 2 → Cl 2 + NO 3 and was found to be 0.73 ± 0.14 at 308.15 nm, 0.60 ± 0.12 at 248.25 nm, and 0.45 ± 0.08 at 193 nm. The estimated O atom yields were <0.4 at 248.25 nm and <0.9 at 193 nm. Quoted error limits are at the 95% confidence level and include estimated systematic errors. The results from this study are compared with those from previous studies. On the basis of this work and that of Goldfarb et al. (Goldfarb, L.; Schmoltner, A.-M.; Gilles, M. K.; Burkholder, J. B.; Ravishankara, A. R. J. Phys. Chem. 1997, 101, 6658.), it is concluded that Cl and NO 3 are the major products in the photolysis of ClONO 2 at wavelengths important in the stratosphere and that the total quantum yield for dissociation is close to 1. The implications of these findings to stratospheric chemistry are discussed.