Transient infrared spectra of CH3SOO and CH3SO observed with a step-scan Fourier-transform spectrometer

Abstract

A step-scan Fourier-transform spectrometer coupled with a multipass absorption cell was employed to monitor time-resolved infrared absorption of transient species produced upon irradiation at 248 nm of a flowing mixture of CH3SSCH3 and O-2 at 260 K. Two transient bands observed with origins at 1397 +/- 1 and 1110 +/- 3 cm(-1) are tentatively assigned to the antisymmetric CH3-deformation and O-O stretching modes of syn-CH3SOO, respectively; the observed band contour indicates that the less stable anti-CH3SOO conformer likely contributes to these absorption bands. A band with an origin at 1071 +/- 1 cm(-1), observed at a slightly later period, is assigned to the S=O stretching mode of CH3SO, likely produced via secondary reactions of CH3SOO. These bands fit satisfactorily with vibrational wavenumbers and rotational contours simulated based on rotational parameters of syn-CH3SOO, anti-CH3SOO, and CH3SO predicted with density-functional theories B3LYP/aug-cc-pVTZ and B3P86/aug-cc-pVTZ. Two additional bands near 1170 and 1120 cm(-1) observed at a later period are tentatively assigned to CH3S(O)OSCH3 and CH3S(O)S(O)CH3, respectively; both species are likely produced from self-reaction of CH3SOO. The production of SO2 via secondary reactions was also observed and possible reaction mechanism is discussed. (C) 2010 American Institute of Physics. [doi:10.1063/1.3495765]