State-to-state integral cross sections for the Cl + CHD3 (vCH = 0,1) → HCl + CD3 reactions

To precisely study the effect of CH stretch excitation, we calculate the first seven-dimensional state-to-state integral cross sections (ICSs) for the Cl + CHD3(vCH = 0,1) → HCl + CD3 reactions using the time-dependent wave-packet approach on a highly accurate fundamental invariant neural network potential energy surface. Compared to experiments that focus solely on CD3(v2 = 0), our theoretical calculations give a more global picture. It is found that the vibrational enhancement factors of the total ICS are less than 1 only in the very low collision energy region (<0.55 kcal/mol); moreover, the CH stretch-excited reaction also produces vibrationally cold HCl. These two findings indicate that Polanyi's rules apply to this late-barrier polyatomic reaction, not only in terms of the energy requirement in the breaking bond but also in the energy disposal in the newly formed bond. In addition, although the experimental and theoretical product HCl(v1 = 1) branching fractions for CD3(v2 = 0) are in quantitative agreement, the new quantum vibrational enhancement factor for CD3(v2 = 0) is ∼2.7 times greater than the experimental results.