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

The non-adiabatic transition state theory (NA-TST) coupling with master equation (ME) method was adopted to study the kinetics of the spin-forbidden recombination reaction SO₂+O(³P) (+M)→SO₃ (+M). The minimum energy crossing point (MECP) was determined and the low-pressure limit (LPL) rate constants at different temperatures were found to be consistent with the reported experimental data.

Abstract

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(³P) (+M)→SO₃ (+M). By determining the minimum energy crossing point (MECP) of the triplet-singlet potential energy surfaces, the high-pressure limit (HPL), k _∞=3.81×10⁸ T^0.998 e^−1214/T cm³ mol⁻¹ s⁻¹ and the low-pressure limit (LPL), k ₀=4.78×10³⁶ T^−6.38 e^−4610/T cm⁶ 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.

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