Chemical Dynamics of the OH and OD Radical Reactions with H2S, CH3SCH3, and CH3SH Studied by Infrared Chemiluminescence

The infrared chemiluminescence of H 2 O and HOD molecules formed from the room-temperature reactions of OH and OD radicals with H 2 S, CH 3 SCH 3, and CH 3 SH was recorded by viewing a fast-flow reactor with a Fourier transform spectrometer. Nascent vibrational distributions of the H 2 O and HDO product molecules were obtained by computer simulation of the infrared spectra. According to our assignments for the v 3 = 0 populations, the vibrational distributions of HDO from the H 2 S and CH 3 SCH 3 reactions were inverted in the O−H stretching mode with a maximum in v 3 = 2 and v 3 = 1, respectively, and the fraction of the available energy released as vibrational energy is 〈 f v 〉 ≈ 0.6 with ∼25−30% of the vibrational energy in the bending coordinate. The reaction with CH 3 SH gives a HOD vibrational distribution that declines with increased v 3; 〈 f v 〉 is only ≈0.4, but 40% of the vibrational energy is in the bending mode. For each reaction, the vibrational distributions for H 2 O closely resemble those for HOD, after allowance is made for the collision-induced equilibration between the ν 1 and ν 3 modes of H 2 O and the ν 1 and 2ν 2 modes of HOD. The reduced vibrational energy disposal to H 2 O and HOD from CH 3 SH is taken as evidence for a mechanism that differs from the direct abstraction process for the H 2 S and CH 3 SCH 3 reactions. These results are analyzed using information theory, and they also are compared with the data from similar reactions of hydroxyl radicals and F atoms. Secondary reactions of the sulfur-containing primary radicals (SH, CH 3 S, and CH 3 SCH 2 ) with NO 2 and NO are discussed.