Infrared absorption of CH3OSO detected with time-resolved Fourier-transform spectroscopy

Abstract

A step-scan Fourier-transform spectrometer coupled with a multipass absorption cell was employed to detect temporally resolved infrared absorption spectra of CH3OSO produced upon irradiation of a flowing gaseous mixture of CH3OS(O)Cl in N-2 or CO2 at 248 nm. Two intense transient features with origins near 1152 and 994 cm(-1) are assigned to syn-CH3OSO; the former is attributed to overlapping bands at 1154 +/- 3 and 1151 +/- 3 cm(-1), assigned to the S=O stretching mixed with CH3 rocking (nu(8)) and the S=O stretching mixed with CH3 wagging (nu(9)) modes, respectively, and the latter to the C-O stretching (nu(10)) mode at 994 +/- 6 cm(-1). Two weak bands at 2991 +/- 6 and 2956 +/- 3 cm(-1) are assigned as the CH3 antisymmetric stretching (nu(2)) and symmetric stretching (nu(3)) modes, respectively. Observed vibrational transition wavenumbers agree satisfactorily with those predicted with quantum-chemical calculations at level B3P86/aug-cc-pVTZ. Based on rotational parameters predicted at that level, the simulated rotational contours of these bands agree satisfactorily with experimental results. The simulation indicates that the S=O stretching mode of anti-CH3OSO near 1164 cm(-1) likely makes a small contribution to the observed band near 1152 cm(-1). A simple kinetic model of self-reaction is employed to account for the decay of CH3OSO and yields a second-order rate coefficient k =(4 +/- 2) x 10(-10) cm(3) molecule(-1) s(-1). (C) 2011 American Institute of Physics. [doi: 10.1063/1.3556817]