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 th e room-temperature reactions of OH and OD radicals with H2S, CH3SCH3, and CH3SH was recorded by viewing a fast-flow reactor with a Fourier t ransform spectrometer. Nascent vibrational distributions of the H2O an d HDO product molecules were obtained by computer simulation of the in frared spectra. According to our assignments for the nu 3 = 0 populati ons, the vibrational distributions of HDO from the H2S and CH3SCH3 rea ctions 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 e nergy released as vibrational energy is ([f nu],) approximate to 0.6 w ith similar to 25-30% of the vibrational energy in the bending coordin ate. The reaction with CH3SH gives a HOD vibrational distribution that declines with increased nu(3); [f(nu)] is only approximate to 0.4, bu t 40% of the vibrational energy is in the bending mode. For each react ion, the vibrational distributions for H2O closely resemble those for HOD, after allowance is made for the collision-induced equilibration b etween the nu(1) and 2(nu 2) modes of H2O and the nu(1) and 2 nu(2) mo des of HOD. The reduced vibrational energy disposal to H2O and HOD fro m CH3SH is taken as evidence for a mechanism that differs from the dir ect abstraction process for the H2S and CH3SCH3 reactions. These resul ts are analyzed using information theory, and they also are compared w ith the data from similar reactions of hydroxyl radicals and F atoms. Secondary reactions of the sulfur-containing primary radicals (SH, CH3 S, and CH3SCH2) with NO2 and NO are discussed.