LIF study of the reactions of the IO radical with NO and NO2 over an extended range of temperature and pressure

A pulsed laser-photolysis / pulsed laser induced fluorescence technique was used to investigate the kinetics of the reactions of the IO radical with NO and NO2. For the reaction (1) IO + NO → I + NO2 the rate constants between 233 and 346 K were found to be kIO+NO(T) = (4.3 ± 1.0) × 10−12exp[(397 ± 65) K/T] cm3 s−1, independent of pressure between 13 and 130 mbar as measured at 286 K. Reaction (2) IO + NO2 + M → IONO2 + M has been studied between 48 and 402 mbar in the temperature range 238–298 K. The rate constants were found to be in the fall-off region between second- and third-order kinetics for this pressure range. Assuming a broadening factor of FC = 0.6, independent of temperature, a set of fall-off parameters with k0(T) = 4.1 × 10−31 (T/298 K)−6.3 cm6 s−1 and k∞ = 1.0 × 10−11 cm3 s−1 was found to adequately describe the data.