A laser-induced fluorescence study of the O(3P) + CF3I and IO + NO reactions: Evidence for an association channel for O + CF3I at low temperatures

The reaction O(3P)+CF3I→k1products was monitored by the detection of the product IO using laser-induced fluorescence at 445 nm, with generation of O(3P) via 248 nm photolysis of O3 or 193 nm photolysis of N2O. The temporal evolution of IO as a function of [CF3I] was used to determine the rate coefficient, k1, in the temperature range 223–523 K at a variety of pressures. At 223 K, a pressure dependence of k1 was observed, indicative of an association channel, and for N2 bath gas the third-order rate coefficient was estimated as kassoc=(5.5±2)×10−31 cm6 molecule−1 s−1. For T>223 K, k1 was found to be independent of pressure and was described by the Arrhenius expression: k1(T)=(9.9±1.0)×10−12 exp−(1930±800)RT cm3 molecule−1 s−1The rate coefficient for the reaction IO+NO→k2products was measured at T=294 K to be k2=(1.82±0.1)×10−11 cm3 molecule−1 s−1, and independent of pressure.