High Temperature Reaction of S + SO₂ → SO + SO: Implication of S₂O₂ Intermediate Complex Formation

Abstract

The rate constant for the reaction S + SO2 → SO + SO (1) has been investigated by measuring time profiles of S atoms behind reflected shock waves using two experimental systems: S atoms were provided by the thermal decomposition of COS in the high-temperature range (2020−2800 K) and by excimer laser photolysis of COS in the low-temperature range (T = 1120−1540 K). The results of these experiments yield the rate constant with a non-Arrhenus temperature dependence, k1 = 10-39.73T8.21 exp(4828.5/T) cm3 molecules-1 s-1, over the extended temperature range (1120−2800 K). By comparing the rate constants with that derived from a conventional transition-state theory based on the potential energy surface calculated by the G2M(CC1) methodology, a reaction mechanism including a contribution of the singlet state of the reaction intermediate S2O2 is discussed.