Quantum chemical and theoretical kinetics studies on the reaction of carbonyl sulfide with H, OH and O(3P)

The potential energy surfaces for the reaction of COS with H, OH and O(3P) are explored by using various quantum chemical methods including W1BD, CBS-QB3, G4, G3B3, CCSD(T), QCISD(T), CCSD, QCISD, M06-2X, B2PLYPD, mPW2PLYPD, ωB97X-D and BB1K. Transition state theory and a modified strong collision/RRKM model are employed to calculate the thermal rate coefficients for the formation of major products as a function of temperature and pressure. The computed rate constants and branching ratios are compared with the available experimental data. It is found that the reaction of hydrogen atom with carbonyl sulfide is the fastest chemical sink for COS degradation. The calculated rate coefficients for COS + OH reaction, at various temperatures and pressures, are in accordance with the experimental observations denying the importance of this reaction in the atmosphere.