Oxidation of S and SO by O2 in high‐temperature pyrolysis and photolysis reaction systems

The reaction of S atoms with O2 was studied behind reflected shock waves applying atomic resonance absorption spectroscopy (ARAS) for concentration measurements of S and O atoms. S atoms were generated either by laser‐flash photolysis (LFP) of CS2 or by the high‐temperature pyrolysis of COS, respectively. The concentrations of O2 in the mixtures ranged between 50 ppm and 400 ppm, and those of the S precursors, CS2 and COS, between 5 and 25 ppm. The rate coefficient of the reaction equation image was determined from the observed decay of the S absorption signals for temperatures 1220 K ⩽ T ⩽ 3460 K. The measured O‐atom concentration profiles in COS/O2/Ar reaction systems were evaluated, using simplified kinetic mechanism, to verify the given rate coefficient k5. In experiments with the highest value of the [O2]/[COS] ratio the measured O‐atom concentrations were found to be sensitive to the reaction: equation image The fitting of the calculated O‐atom profiles to the measured ones results in mean value of: which is to be valid for the temperature range 2570 K ⩽ T ⩽ 2980 K. A first‐order analysis of the observed S absorption decay in LFP shock wave experiments on CS2/Ar gas mixtures resulted in a rate coefficient of the background reaction (R4): equation image for temperatures 1260 K ⩽ T ⩽ 1820 K.