INFRARED ABSORPTION OF CH$_{3}$SO$_{2}$ DETECTED WITH TIME-RESOLVED FOURIER-TRANSFORM SPECTROSCOPY
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Date
2006
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Ohio State University
Abstract
A step-scan Fourier-transform spectrometer coupled with a 6.4-m multipass absorption cell was employed to detect time-resolved infrared absorption spectra of the reaction intermediate CH$_{3}$SO$_{2}$ radical, produced upon irradiation of a flowing mixture of CH$_{3}$I and SO$_{2}$ in CO$_{2}$ at 248 nm. Two transient bands with origins at 1280 and 1076 cm$^{-1}$ were observed and assigned to the SO$_{2}$-antisymmetric and SO$_{2}$-symmetric stretching modes of CH$_{3}$SO$_{2}$, respectively. Calculations with density-functional theory (B3LYP/aug-cc-pVTZ and B3P86/aug-cc-pVTZ) predicted the geometry, vibrational wave numbers, and rotational parameters of CH$_{3}$SO$_{2}$ and CH$_{3}$OSO. Based on predicted rotational parameters, the simulated absorption band of SO$_{2}$-antisymmetric stretch which is dominated by the b-type rotational structure agrees satisfactorily with experimental results. In addition, a band near 1159 cm$^{-1}$ was observed at a later period and was attributed to CH$_{3}$SO$_{2}$I. The reaction kinetics of CH$_{3}$ + SO$_{2}$ = CH$_{3}$SO$_{2}$ and CH$_{3}$SO$_{2}$ + I = CH$_{3}$SO$_{2}$I based on the rise and decay of absorption bands of CH$_{3}$SO$_{2}$ and CH$_{3}$SO$_{2}$I agree satisfactorily with previous reports.
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Author Institution: Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan; Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, Hsinchu 30010, Taiwan and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan