Experimental and theoretical investigations of rate coefficients of the reaction S(3P)+O2 in the temperature range 298–878 K

Rate coefficients of the reaction S+O2 with Ar under 50 Torr in the temperature range 298–878 K were determined with the laser photolysis technique. S atoms were generated by photolysis of OCS with a KrF excimer laser at 248 nm; their concentration was monitored via resonance fluorescence excited by atomic emission of S produced from microwave-discharged SO2. Our measurements show that k(298 K)=(1.92±0.29)×10−12 cm3 molecule−1 s−1, in satisfactory agreement with previous reports. New data determined for 505–878 K show non-Arrhenius behavior; combining our results with data reported at high temperatures, we derive an expression k(T)=(9.02±0.27)×10−19T2.11±0.15 exp[(730±120)/T] cm3 molecule−1 s−1 for 298⩽T⩽3460 K. Theoretical calculations at the G2M (RCC2) level, using geometries optimized with the B3LYP/6-311+G(3df) method, yield energies of transition states and products relative to those of the reactants. Rate coefficients predicted with multichannel RRKM calculations agree satisfactorily with experiment...