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

Abstract

Accurate quantum dynamics of the chemical reaction O( ³ P)+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 _i 5. 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.