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

Abstract

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.