Quantum scattering on coupled ab initio potential energy surfaces for the Cl(2P)+HCl→ClH+Cl(2P) reaction

We present the results of accurate quantum dynamical calculations for the Cl(P-2) + HCl --> ClH + Cl(P-2) reaction using a coupled channel reactive scattering method based on hyperspherical coordinates. The calculations include the three potential energy surfaces (1(2)A', 2(2)A' and 1(2)A ") that correlate to the ground states of the reactants and products, as well as electrostatic, Coriolis and spin-orbit couplings. The electrostatic surfaces and couplings are taken from the high quality ab initio computations of A. J. Dobbyn, J. N. L. Connor, N.A. Besley, P. J. Knowles and G. C. Schatz [Phys. Chem. Chem. Phys., 1999, 1, 957], with the barrier heights scaled so that thermal rate coefficients derived from the scattering calculations agree with experimental data. Only the total angular momentum quantum number J = 1/2 partial wave is calculated; state selected and thermal rate coefficients are obtained using a J-shifting approximation. We study basis set convergence and compare single and multiple surface results, with emphasis on state selected and total cumulative reaction probabilities and thermal rate coefficients, including branching between ground and excited spin-orbit states. The contribution of resonances to the scattering is discussed and analysed. We also compare with scattering results using an earlier, more approximate, set of potential surfaces and couplings due to C. S. Maierle, G. C. Schatz, M. S. Gordon, P. McCabe and J. N. L. Connor [J. Chem. Soc., Faraday Trans., 1997, 93, 709].