TEMPERATURE-DEPENDENCE OF THE REACTION BETWEEN O(P(3)) AND OCLO AT LOW-PRESSURE

The rate coefficient for the reaction O(3p) + OClO has been measured a t low pressure (1-5 Torr) over the temperature range 200400 K. The exp eriments were performed in a discharge flow system with atomic resonan ce fluorescence detection of O(3P). The ratio of [OClO]/[O] was kept v ery high (usually 10(3)-10(4)) in order to avoid secondary reactions. At 298 K, k = (1.0 +/- 0.3) X 10(-13) molecules-1 cm3 s-1, which is co nsistent with recent results obtained at high pressure (8-800 Torr arg on) and extrapolated to zero pressure. In the present low-pressure exp eriments, the rate coefficient increases with increasing temperature f rom 243 to 400 K while from 200 to 225 K the rate coefficient decrease s with increasing temperature. The Arrhenius expression for the 243-40 0 K region is k = (2.4 +/- 0.8) X 10(-12) exp[(-960 +/- 120)/T] molecu le-1 cm3 s-1. The trend observed here for T = 243-400 K is opposite to that inferred from the extrapolation of high-pressure results (20-600 Torr argon) at T = 248-312 K. Our high-temperature results (243-400 K ) are consistent with the bimolecular abstraction channel, O(3P) + OCl O --> ClO + O2.