Influence of van der Waals wells on the quantum scattering dynamics of the Cl(2P) + HCl → ClH + Cl(2P) reaction

We investigate the influence of van der Waals wells on the quantum scattering dynamics of the Cl + HCl → ClH + Cl reaction in which the three electronic states that correlate asymptotically to the ground state of Cl(2P) + HCl(1Σ+) are included in the dynamical calculations. The short range region of the potential energy surfaces is taken from recent restricted open-shell coupled-cluster singles doubles with perturbative triples and multireference configuration-interaction ab initio computations of Dobbyn et al. [Phys. Chem. Chem. Phys. 1 (1999) 957], as refined by Whiteley et al. [Phys. Chem. Chem. Phys. 2 (2000) 549]. The long range van der Waals region of the potential surfaces is derived from multisurface empirical potentials due to Dubernet and Hutson [J. Phys. Chem. 98 (1994) 5844]. We manipulate the van der Waals portions of the global potential surfaces by scaling the interaction of the Cl quadrupole with the HCl multipoles. This results in van der Waals wells that are either deeper or shallower than the unscaled reference case. Spin-orbit coupling is included using a spin-orbit parameter that is assumed to be independent of nuclear geometry, and Coriolis interactions are calculated accurately. Reactive scattering calculations have been performed for total angular momentum quantum number, J=1/2, using a hyperspherical-coordinate coupled-channel method in full dimensionality. We investigate how the cumulative reaction probability and the fine-structure-resolved cumulative reaction probabilities are influenced by variations in the van der Waals wells.