Theoretical Study on the Rate Constant of Spin-forbidden Reaction SO2+O(3P) (+M)→SO3 (+M)

To improve the understanding of the oxidation of SO2 to SO3, the non-adiabatic transition state theory (NA-TST) coupling with the master equation (ME) method was adopted to study the kinetic characteristics of the spin-forbidden recombination reaction SO2+ O(P-3) (+ M) -> SO3 (+ M). By determining the minimum energy crossing point (MECP) of the triplet-singlet potential energy surfaces, the high-pressure limit (HPL), k(infinity)= 3.81x10(8) T(0.998)e (-1214/T)cm(3)mol(-1) s(-1) and the low-pressure limit LPL), k(0)= 4.78x10(36) T-6.38 e(-4610/T)cm(6)mol(-2) s(-1) were obtained, respectively. The LPL rate constants were compared with the reported experimental data and good consistency was found. Besides, the hopping probability near the MECP was also determined. In addition, this work shows the potential application of NA-TST/ME method to investigate the kinetics of similar spin-forbidden reactions.