A kinetic study of the very fast reaction: O(3P)+CS→CO‡ +S(3P)

The fast reaction O(3P)+CS→CO‡+S(3P)[Eq .(1)] was studied using a novel flow tube technique in which decay of CS was monitored in the presence of much smaller O(3P) concentrations maintained by rapid O(3P) regeneration via S(3P)+O2→SO+O(3P) [Eq. (2)]. Several measurements of the rate constant for Eq. (1) yield k1= (1.35±0.22) ×1010 liter/mole-sec at 300 °K. The chain reaction consisting of Eqs. (1)+(2), known to be important in many CO chemical laser systems, was shown to have a chain length of ∼50 in the low-pressure (1–2 torr) flow tube. It is concluded that the major chain termination step is not likely to be a homogeneous bimolecular or termolecular reaction of S(3P) or O(3P). Possible heterogeneous chain-breaking reactions are discussed. The implications of our results with respect to stoichiometry assumptions made by other workers in the determination of rate parameters for the important reaction of O(3P) with CS2 are also discussed.