Chemical dynamics of the OH and OD radical reactions with H2S, CH3SCH3, and CH3SH studied by infrared chemiluminescence

The infrared chemiluminescence of H2O and HOD molecules formed from the room-temperature reactions of OH and OD radicals with H2S, CH3SCH3, and CH3SH was recorded by viewing a fast-flow reactor with a Fourier transform spectrometer. Nascent vibrational distributions of the H2O and HDO product molecules were obtained by computer simulation of the infrared spectra. According to our assignments for the nu 3 = 0 populations, the vibrational distributions of HDO from the H2S and CH3SCH3 reactions were inverted in the O-H stretching mode with a maximum in nu(3) = 2 and nu(3) = 1, respectively, and the fraction of the available energy released as vibrational energy is ([f nu],) approximate to 0.6 with similar to 25-30% of the vibrational energy in the bending coordinate. The reaction with CH3SH gives a HOD vibrational distribution that declines with increased nu(3); [f(nu)] is only approximate to 0.4, but 40% of the vibrational energy is in the bending mode. For each reaction, the vibrational distributions for H2O closely resemble those for HOD, after allowance is made for the collision-induced equilibration between the nu(1) and 2(nu 2) modes of H2O and the nu(1) and 2 nu(2) modes of HOD. The reduced vibrational energy disposal to H2O and HOD from CH3SH is taken as evidence for a mechanism that differs from the direct abstraction process for the H2S and CH3SCH3 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, CH3S, and CH3SCH2) with NO2 and NO are discussed.