Reaction mechanism of atomic oxygen with hydrogen sulfide at high temperature

The reaction of atomic oxygen (³P) with hydrogen sulfide was investigated by the shock tube/laser photolysis method at high temperatures (1100-2000 K), where the time dependence of O and H atoms was monitored with atomic resonance absorption spectrometry (ARAS). O atoms were produced by the photolysis of SO₂ by a KrF excimer laser behind reflected shock waves. The overall rate constant for the reaction O + H₂S → products (1) was determined from the decay rate of the absorption of O atoms as k₁ = (2.5 ± 0.6) × 10^-10 exp[-(32 ± 4) kJ mol^-1/RT] cm³ molecule^-1 s^-1. The branching fraction for the substitution channel O + H₂S → H + HSO (1c) was determined by measuring the concentration of H atoms relative to the initial production of O atoms, that is, k_1c/k₁ = 0.2 ± 0.1 at 1520-1820 K. The rate constant k₁ and the branching fraction k_1c/k₁ were also evaluated based on the conventional transition state theory with the Wigner's tunneling correction for the potential energies. The branching fraction determined in this study was found to be consistent with TST calculation.