A full-dimensional time-dependent wave packet study of the OH + CO → H + CO2 reaction

Abstract

Full-dimensional time-dependent wave packet calculations were made to study the \(\hbox{OH}+\hbox{CO} \rightarrow \hbox{H}+\hbox{CO}_2\) reaction on the Lakin–Troya–Schatz–Harding potential energy surface. Because of the presence of deep wells supporting long-lived collision complex, one needs to propagate the wave packet up to 450,000 a.u. of time to fully converge the total reaction probabilities. Our calculation revealed that the CO bond was substantially excited vibrationally in the complex wells, making it necessary to include sufficient CO vibration basis functions to yield quantitatively accurate results for the reaction. We calculated the total reaction probabilities from the ground initial state and two vibrationally excited states for the total angular momentum J = 0. The total reaction probability for the ground initial state is quite small in magnitude with many narrow and overlapping resonances due to the small complex-formation reaction probability and small probability for complex decaying into product channel. Initial OH vibrational excitation considerably enhances the reactivity because it enhances the probability for complex decaying into product channel, while initial CO excitation has little effects on the reactivity. We also calculated the reaction probabilities for a number of J > 0 states by using the centrifugal sudden approximation. By doing some calculations with multiple K-blocks included, we found that the centrifugal sudden approximation can be employed to calculate the rate constant for the reaction rather accurately. The calculated rate constants only agree with experimental measurements qualitatively, suggesting more theoretical studies be carried out for this prototypical complex-formation four-atom reaction.