Experimental Kinetic Study of the Reactions of Atomic Chlorine with H2S, SH, and OCS

Abstract The reactions of Cl atoms with H2S, SH, and OCS, of interest for atmospheric chemistry, were studied at a total pressure of 2 Torr as a function of temperature in a low-pressure discharge flow-tube reactor with mass spectrometric detection of the species involved. The rate constants of the reactions Cl + H2S → SH + HCl (1) and Cl + OCS → SCl + CO (3) were determined under pseudo-first-order conditions, monitoring the kinetics of consumption of chlorine atoms under conditions of excess molecular reagent: k1 = (3.72 ± 0.08) × 10–11 exp((209 ± 7)/T) cm3 molecule–1 s–1 (T = 220–960 K) and k3 = (2.6 ± 1.5) × 10–10 exp(−(8440 ± 520)/T) cm3 molecule–1 s–1 (T = 755–1000 K), with estimated total uncertainties of 15% and 20%, respectively, at all temperatures. The rate constant of chlorine atoms with SH, an important intermediate in the oxidation of sulfur-containing compounds, Cl + SH → S + HCl (2), was determined at T = 220–960 K by monitoring the kinetics of the SH radical in reaction (1) carried out in excess of Cl atoms: k2 = (1.23 ± 0.03) × 10–10 exp((90 ± 9)/T) cm3 molecule–1 s–1, with a conservative (temperature-independent) uncertainty of 20%. The kinetic data from the present study are compared with previous measurements and theoretical calculations.