Kinetics of the reaction of HO2 with ozone

Rate constants were measured for the reaction HO2+O3→OH+2O2(k1) using a discharge-flow system with laser magnetic resonance detection of both HO2 and OH. k1 was determined directly from the first order decay of HO2 in excess O3 when C2F3Cl was added to scavenge the OH product and prevent interference from the faster reaction OH+O3→HO2+O2(k2). The ratio k2/k1 was independently determined from the steady-state [HO2]/[OH] ratio obtained without C2F3Cl. Results from the scavenger method are given by k1= (1.4±0.4)×10−14 exp [−(580±100)/T] cm3 s−1 for 245 K<T<365K. Results of the ratio measurements are in good agreement with these data when combined with a directly measured value of k2?1.0)×10−14 cm3 s−1 at 300 K. These measurements are compared with other studies and some implications for stratospheric ozone chemistry are discussed.