Quantum dynamics of O(³P)+HCl→OH+Cl Effects of reagent rotational excitation

Abstract

Accurate quantum dynamics of the chemical reaction O(³P)+HCl(j_i, v_i=0)→OH(j_f, v_f=0)+Cl is studied using the hyperspherical coordinate approach and the Koizumi–Schatz–Gordon (KSG) potential-energy surface. The effects of reagent rotational excitation on the dynamics are investigated. The study considers total energies up to 0.7 eV and reagent rotational states, j_i=0–10. The total reaction cross-section shows a strong dependence on j_i. Initially it decreases with increasing j_i, up to j_i≈4, and then increases with further increase in j_i. This overall trend is enhanced on increasing the total energy. The final rotational state (j_f) distributions are also investigated. Interestingly, the distribution shows a peak at high j_f (≈10) irrespective of j_i and the total energy. The qualitative features are quite similar to the experimental results. Finally, the state-resolved rate constant and the thermal rate constant are evaluated. Because of the enhancement of the reaction by the reagent rotational excitation, the state-resolved rate constants for 8j_i⩽10 are two or three orders of magnitude larger than those for j_i5. The thermal rate constant obtained is thus much larger than the experimental data implying that the barrier height of the KSG surface may be too low.

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