Quasiclassicaltrajectorystudyof thereactionH2+OH→H2O+H: Comparison with quantum results

Abstract

We report a study on the reaction H ₂ +OH↔H ₂ O+H by computing quasiclassical trajectories on the same potential-energy surface as recent exact quantum scattering calculations. We calculate reagent state-selected cross-sections and J=0 probabilities, J=0 total cumulative probabilities and thermal rate constants. We performed a rigorous comparison with quantum results, both exact (J=0 probabilities) and approximate (cross-sections and rate constants). Generally, quantum and QCT results agree remarkably well, except for vibrationally excited H ₂ , where quantum results show a rich resonance structure. There is very good agreement between QCT and quantum cumulative probabilities above the quantum threshold. However, due to the usual tunnelling effect the agreement for the rate constants is less good, especially at low temperatures where quantum results are 30–50% above the QCT ones. Finally, by computing J-shifted QCT rate constants, we found that the errors introduced by the J-shifting approximation are of the same order as those introduced by QCT.