Reactive Resonances in the Cl + CHD3(vCH = 1) → HCl + CD3 Reaction

The stretch excited Cl + CHD3(vCH = 1) → HCl + CD3 reaction is experimentally known to involve resonances supported by a significant chemical bond-softening vibrational adiabatic potential well located at the transition state; however, theoretical differential cross sections (DCSs) that can be directly compared with experiments, as well as a detailed theoretical analysis of the resonances, remain lacking. In this Letter, we report the first seven-dimensional state-to-state quantum DCS for this reaction at collision energies up to 0.1 eV on a highly accurate fundamental invariant neural network potential energy surface. The product vibrational and rotational state distributions, as well as the angular distributions, yield qualitative agreement with available experimental results. For the HCl(v1 = 0) + CD3(v2 = 0-4) channels, we observed two distinctive peaks at Ec = 0.004 and 0.056 eV in the backward-scattering DCS, originating from Feshbach resonances via vibrationally nonadiabatic decay. The predominantly forward-scattered HCl(v1 = 1) + CD3(v2 = 0) products are attributed to shape resonances of the Cl···H···CD3 complex, which exhibit an intricate nodal structure in the scattering wave function due to the heavy-light-heavy character of the system.