Temperature-Dependent Kinetic Study of the Reactions of Hydrogen Atoms with H 2 S and C 2 H 4 S.

A discharge-flow reactor combined with modulated molecular beam mass spectrometry technique was employed to determine the rate constants of H-atom reactions with hydrogen sulfide and thiirane. The rate constants for both reactions were determined at a total pressure of 2 Torr from 220 to 950 K under pseudo-first-order conditions by monitoring either consumption of H atoms in excess of H 2 S (C 4 H 4 S) or the molecular species in excess of atomic hydrogen. For H + H 2 S reaction, a suggested previously strong curvature of the Arrhenius plot was confirmed: k l = 8.7 × 10 -13 × ( T /298) 2.87 × exp(-125/ T ) cm 3 molecule -1 s -1 with a conservative uncertainty of 15% at all temperatures. Non-Arrhenius behavior was also observed for the reaction of H-atom with C 2 H 4 S, with the experimental rate constant data being best fitted to a sum of two exponential functions: k 2 = 1.85 × 10 -10 exp(-1410/ T ) + 4.17 × 10 -12 exp(-242/ T ) cm 3 molecule -1 s -1 with an independent of temperature uncertainty of 15%.