The atmospheric chemistry of dimethylsulfoxide (DMSO) kinetics and mechanism of the OH + DMSO reaction

We have employed a pulsed laser photolysis-pulsed laser induced fluorescence technique to study the kinetics and mechanism of the reaction of OH with dimethylsulfoxide and its deuterated analogue. A rate coefficient of (1.0 ± 0.3) x 10^-10 cm³ molecule^-1 s^-1 was obtained at room temperature. The rate coefficient was independent of pressure over the range 25-700 Torr, showed no dependence on the nature of the buffer gas and showed no kinetic isotope effect. A limited study of the temperature dependence indicated that the reaction displays a negative activation energy. The gas phase ultraviolet absorption spectrum was obtained at room temperature and showed a strong absorption feature in the far ultraviolet. The absolute absorption cross-section at 205 nm, the absorption peak, is (1.0 ± 0.3) x 10-^-17 cm², where the large uncertainty results from experimental difficulties associated with the low vapor pressure and 'stickiness' of DMSO.