We have investigated production of carbon-and sulfur-containing end products of the OH-initiated oxidation of CS2 in the presence of 02, an important atmospheric chemical reaction which is known to proceed via the following three elementary steps: O H + CS2 + M CSzOH + M; CS20H + 0 2 -products. Two different experimental approaches were employed. In one set of experiments (CP-FTIR studies) continuous photolysis of CH30NO/NO/CS2/Air mixtures at 298 K and 700-Torr total pressure was combined with product detection by Fourier transform infrared spectroscopy; these studies measured moles of products formed per mole of CS2 consumed. In a second set of experiments (LFP-TDLAS studies) 248-nm laser flash photolysis of H202/ CS2/N20/He/02 mixtures at 298 K and 25-100-Torr total pressure was combined with product detection by time-resolved tunable diode laser absorption spectroscopy; in this case, the quantity measured was moles of product formed per mole of O H consumed. In both studies OCS and CO are observed as carbon-containing products with yields of 0.83 f 0.08 and 0.16 f 0.03, respectively; uncertainties represent estimates of absolute accuracy at the 95% confidence level. The LFP-TDLAS experiments demonstrate that the above yields represent "prompt" product formation; i.e., OCS and CO are formed either as primary products of the CSzOH + 0 2 reaction or as products of a fast (k > cm3 molecule-' s-') secondary reaction of a primary product with 0 2 . The CP-FTIR experiments show that, under atmospheric conditions, SO2 is produced with a yield of 1.1 5 f 0.10; in this case, the LFP-TDLAS results strongly suggest that only about three-fourths of the SO2 is formed as a prompt product, with the remainder generated via slow reaction of SO (generated as a prompt product of the CS2OH + 0 2 reaction) with 0 2 . The implications of our results for understanding the detailed mechanism of the very complex CS2OH + 0 2 reaction are discussed, as are their implications for understanding the atmospheric cycles of CS2 and OCS.

The kinetics of the title reaction have been investigated at 298 K using time‐resolved long‐pathlength absorption spectroscopy to monitor the temporal behavior of IO following 351‐nm laser flash photolysis of NO2/I2/CH3SCH3(DMS)/N2/O2 mixtures. We obtain an upper limit bimolecular rate constant for the IO+DMS reaction of 3.5×0−14 cm3 molecule−1 s−1; this upper limit is nearly 3 orders of magnitude slower than two previously reported measurements. Our results suggest that coupling of the marine sulfur and iodine cycles via the IO+DMS reaction is negligible.

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A laser flash photolysis-long path laser absorption technique has been employed to investigate the kinetics of NO3 reactions with CH3SCH3(kl), CDsSCD3(kz), and CzH5SCzHS(k3) in 500 torr air at 298 K. The dependence of k l on total pressure (20-500 torr) and oxygen partial pressure (0-100 torr) has also been investigated, with no dependence observed. Measured rate coefficients in units of cm3 molecule-' s-' are kl = 13 2 3, k p = 3.4 2 0.8, and k3 = 48 2 12, where the quoted uncertainties are %estimates of absolute accuracy. The magnitude of NO3 + sulfide rate coefficients and negative activation energies for k l (reported by other investigators) suggest that reaction does not proceed via a direct hydrogen abstraction mechanism. However, the reactivity trend observed in this study provides evidence that the reaction mechanism does involve breaking a carbon-hydrogen bond.