Experimental Study of SO2 Formation in the Reactions of CH3SO Radical with NO2 and O3 in Relation with the Atmospheric Oxidation Mechanism of Dimethyl Sulfide

Abstract

Reactions of CH3SO radicals with O3 and NO2 have been studied at 140−660 Torr pressure of N2 and 300 K using the pulsed laser photolysis technique with direct monitoring of SO2 formation by laser induced fluorescence with excitation at 220.6 nm. The yield of SO2 in the reaction of CH3SO with NO2 has been found to be pressure dependent varying from (0.4 ± 0.12) at 100 Torr to (0.25 ± 0.05) at 664 Torr of N2. This result is in agreement with our previous data obtained using different experimental approach and may be interpreted by the formation of activated CH3SO2* radical followed by its prompt decomposition or collisional stabilization. The SO2 yield in the reaction of CH3SO with O3 has been found to be a factor (4.0 ± 0.3) higher than in the reaction with NO2 corresponding to a yield of (1.0 ± 0.12) at 660 Torr of N2. The rate constant for the reactions CH3SO + O3, O + CH3SSCH3, and O + CS2 at 300 K have been found to be (3.2 ± 0.9) × 10-13, (1.06 ± 0.07) × 10-10, and (3.6 ± 0.1) × 10-12 cm3 molecule-1 s...