Experiments and Calculations on Rate Coefficients for Pyrolysis of SO2 and the Reaction O + SO at High Temperatures

Rate coefficients for the pyrolysis of SO2 in Ar in the temperature range 2188−4249 K were determined using a diaphragmless shock tube. The concentration of O atoms was monitored with resonance absorption. Rate coefficients determined in this work show Arrhenius behavior, with k1a(T) = (4.86 ± 1.31) × 10-9 exp [−(50450 ± 730)/T] cm3 molecule-1 s-1; listed errors represent one standard deviation in fitting. These values are consistent with some previous measurements that show a preexponential factor and activation energy greater than other measurements. 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 a microcannonical variational RRKM theory agree well with experimental observations; contributions from electronically excited states of SO2 are significant. Rate coefficients for the recombination O + SO → SO2 are predicted to dec...