Kinetics and mechanism of the reaction of S(³P) with O₂

The kinetics and the mechanism of the reaction of S(³P) with O₂ have been studied at low (293 K) and high (980-1610 K) temperatures. The strong non-Arrhenius behavior of the overall rate constant, which has been inferred from previous measurements, was confirmed. Possible causes of this non-Arrhenius behavior were investigated. No difference was found in the product channel between high and low temperatures, i.e., the products of the reaction were confirmed to be O(³P)+SO at both low (293 K) and high (1566 K) temperatures by quantitative measurements of O(³P) atoms. No pressure dependence was found either in the rate constant or in the product yield in the pressure range 2-50 Torr (Ar buffer) at 293 K. At low temperature, the time profile of each triplet component of S(³P_J) was measured separately. The intratriplet relaxations by collision with O₂ were found to be about one order of magnitude faster than the reaction with O₂. An analysis of the intratriplet relaxation by O₂ strongly suggests the contribution of bound multiplet surfaces, which probably have substantial barriers toward products, O(³P)+SO. These (and/or other) multiplet surfaces probably contribute the steep rise of rate constant at higher temperatures.