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 zprojection 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 Ein 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.