Rate of reaction of OH with COS

The laser/flash photolysis‐resonance fluorescence technique was employed to study the kinetics of the reaction OH + COS → k1 products. Complicating secondary reactions involving COS photofragments were eliminated by using 193 nm laser photolysis of HNO 3 as a source of OH. The rate constant was found to be much slower than previous measurements indicated. Based on our experiments, the upper limit for k 1 at 298K is 8.8 × 10 −15 cm³molecule −1 s −1 . Our results suggest that the title reaction is only a minor COS degradation pathway in the troposphere.