We have performed quantum mechanical (QM) dynamics calculations within the independent-state approximation with new benchmark triplet A″ and A′ surfaces [B. Ramachandran et al., J. Chem. Phys. 119, 9590 (2003)] for the rovibronic state-to-state measurements of the reaction O(3P)+HCl(v=2,j=1,6,9)→OH(v′j′)+Cl(2P) [Zhang et al., J. Chem. Phys. 94, 2704 (1991)]. The QM and experimental rotational distributions peak at similar OH(j′) levels, but the QM distributions are significantly narrower than the measurements and previous quasiclassical dynamics studies. The OH(low j′) populations observed in the measurements are nearly absent in the QM results. We have also performed quasiclassical trajectory with histogram binning (QCT-HB) calculations on these same benchmark surfaces. The QCT-HB rotational distributions, which are qualitatively consistent with measurements and classical dynamics studies using other surfaces, are much broader than the QM results. Application of a Gaussian binning correction (QCT-GB) dramatically narrows and shifts the QCT-HB rotational distributions to be in very good agreement with the QM results. The large QCT-GB correction stems from the special shape of the joint distribution of the classical rotational/vibrational action of OH products. We have also performed QM and QCT calculations for the transition, O+HCl(v=0,T=300 K)→OH(v′j′)+Cl from threshold to ∼130 kcal mol−1 collision energy as a guide for possible future hyperthermal O-atom measurements. We find in general a mixed energy release into translation and rotation consistent with a late barrier to reaction. Angular distributions at high collision energy are forward peaked, consistent with a stripping mechanism. Direct collisional excitation channel cross sections, O+HCl(v=0,T=300 K)→O+HCl(v′=1), in the same energy range are large, comparable in magnitude to the reactive channel cross sections. Although the A″3 state dominates most collision processes, above ∼48 kcal mol−1, the A′3 state plays the major role in collisional excitation.

We report ab initio calculations at the MRCI+Q/CBS level of theory for the ${}^3{A}^{″}$ and ${}^3{A}^{\prime }$ electronic states of the $\mathrm{O}{(}^3\mathrm{P)+}\mathrm{HCl}$ system, where the complete basis set energies are obtained by extrapolating $\mathrm{MRCI}+\mathrm{Q/aug-cc-pV}n\mathrm{Z}\text{\hspace{0.05em}(n=2,3,4)}$ energies. Potential energy surfaces for these electronic states are generated by interpolating these energies using the reproducing kernel Hilbert space method. The reaction barrier on the interpolated ${}^3{A}^{″}$ surface at the MRCI+Q/CBS level of theory is 11.86 kcal/mol. The potential energy surface was then scaled to yield a barrier height close to that predicted by CCSD(T) and MRCI+Q benchmark calculations, namely, 10.60 kcal/mol. The fact that the ${}^3{A}^{″}$ and ${}^3{A}^{\prime }$ electronic states are degenerate at collinear and asymptotic regions of configuration space was used to scale the collinear reaction barrier on the ${}^3{A}^{\prime }$ surface from the MRCI+Q/CBS value of 15.15 kcal/mol to match that of the scaled ${}^3{A}^{″}$ surface, 13.77 kcal/mol. The potential energy surfaces thus obtained appear to be the most accurate to date for the reaction $\mathrm{O}{(}^3\mathrm{P)+}\mathrm{HCl}\to \mathrm{OH}+\mathrm{Cl}.$ The potential energy surface for the ${}^3{A}^{″}$ state contains a fairly deep van der Waals well on the product side of the reaction barrier at a rather sharp O–H–Cl angle (67°) and a shallow well on the reactant side at collinear O–H–Cl geometry. Details of the ab initio calculations, the fitting procedure, and characterization of the saddle and stationary points are presented.