Kinetics of O2(a Δ g ) and I(2P1/2) in the Photochemistry of N2O/I2 Mixtures

The recent demonstration of a discharge-driven oxygen−iodine laser has generated renewed interest in the kinetics of iodine interacting with electronically excited O2 and atomic O. Kinetic measurements that are of relevance to the laser have been carried out using 193 nm pulsed laser photolysis of N2O/I2/CO2 mixtures. Singlet oxygen was generated in this system by the reaction O(1D) + N2O → O2(a 1Δ g , X 3 ) + N2. The fraction of electronically excited O2 produced by this channel was shown to be >0.9. The secondary photochemistry of the N2O/I2/CO2 system was characterized by monitoring the time histories of I(2P1/2), I2, IO, and O2(a). Kinetic modeling of these data was used to determine the rate constant for the deactivation of I(2P1/2) by O(3P) (k = (1.2 ± 0.1) × 10-11 cm3 s-1). Quenching of I(2P1/2) by O(3P) is suppressed in the discharge-driven laser by using NO2 to scavenge the O atoms. The reaction O(3P) + NO2 → O2 + NO is sufficiently exothermic for the production of O2(a), and it has been speculated that this channel may be significant in the laser excitation kinetics. Photolysis of NO2 was used to probe this reaction. O2(a) was not detected, and an upper bound of