A coupled channel hyperspherical scattering study of the Cl + HCl → ClH + Cl reaction: cumulative and state-selected probabilities, integral cross sections, and product rotational distributions

We present accurate quantum results for the Cl + HCl → ClH + Cl reaction using a coupled channel hyperspherical coordinate method (denoted CCH). A semiempirical extended London–Eyring–Polanyi–Sato potential energy surface is employed. In our calculations, the body-fixed z projection quantum number Ω in the rotational basis set has been truncated at Ωmax = 2, since this is sufficient to give converged results near to, and above, the reaction threshold (total energies E in the range 0.40–0.60 eV). We compare our results with earlier work using the centrifugal sudden hyperspherical (CSH) method, in which only Ω = 0 is included in the basis; other features of the calculations are identical. At E = 0.40 eV, where reactivity is low, the CCH(Ωmax = 2) and CSH(Ω = 0) degeneracy averaged reaction probabilities, integral cross sections and product rotational distributions are mostly in excellent agreement. This agreement deteriorates with increasing E, such that at E = 0.60 eV, the CCH(Ωmax = 2) cumulative reaction probability is approximately twice its CSH(Ω = 0) counterpart. Even at E = 0.40 eV there are some important differences between CCH(Ωmax = 2) and CSH(Ω = 0) concerning mj-resolved reaction probabilities. In addition, there are differences in the relative contributions of "tight bend" and "nearly free-rotor" mechanisms to the reaction probabilities and product rotational distributions, with the "nearly free-rotor" mechanism dominant in all cases.