Full-dimensional MRCI-F12 potential energy surface and dynamics of the F(P) + CH → HF + CH reaction.

We report a detailed quasi-classical dynamics study on a new full-dimensional multireference spin-orbit-corrected potential energy surface (PES) for the F(P) + CH → HF + CH reaction. For the PES development, the Robosurfer program package is applied and the MRCI-F12+Q(5,3)/aug-cc-pVDZ energy points are fitted using the monomial symmetrization approach of the permutationally invariant polynomial method. Our simulations provide substantial reaction probabilities and sharply increasing cross sections with an increase in collision energy for this early- and negative-barrier reaction. A direct rebound/stripping mechanism is preferred at low/high collision energies, and the initial translational energy turns out to convert mostly into product recoil, whereas the reaction energy excites the HF vibration. Vibrational and vibrationally resolved rotational state distributions of the HF product obtained from our computations agree well with the single-collision experimental data for the v = 1, 2, and 3 states.