Trajectory surface hopping study of the C + CH reaction
The influence of electronically nonadiabatic transitions in the C(3Pg) + CH(X 2Π) → C2(X 1Σ+g, a 3Πu) + H(2Sg) reaction is investigated by using Tully's fewest-switches version of the trajectory surface hopping method. A diabatic model of the first two 2A′ potential energy surfaces coupled by a conical intersection is used. The diatomic CH has the internal state (ν = 0, j = 0) and batches of 20 000 trajectories are computed for four collision energies, E = 0.1, 0.3, 0.5 and 0.7 eV. We find that the reaction dynamics does not exhibit a statistical character, despite the existence of deep wells along the reaction path. Only the distribution of scattering angle shows a good agreement between trajectories and phase space theory results. A strong excess of vibrational energy is disposed on both electronic products C2(X 1Σ+g) and C2(a 3Πu), correlated with a lack of recoil energy. With all trajectories starting on a single potential surface, we obtain an electronic branching ratio X : a close to 2 : 3, only slightly dependent on the collision energy.