Theoretical investigation of rotationally inelastic collisions of CH(X 2 Π) with hydrogen atoms.

We report calculations of state-to-state cross sections for collision-induced rotational transitions of CH(X2 Π) with atomic hydrogen. These calculations employed the four adiabatic potential energy surfaces correlating CH(X2 Π) + H(2 S), computed in this work through the multi-reference configuration interaction method [MRCISD + Q(Davidson)]. Because of the presence of deep wells on three of the potential energy surfaces, the scattering calculations were carried out using the quantum statistical method of Manolopoulos and co-workers [Chem. Phys. Lett. 343, 356 (2001)]. The computed cross sections included contributions from only direct scattering since the CH2 collision complex is expected to decay predominantly to C + H2 . Rotationally energy transfer rate constants were computed for this system since these are required for astrophysical modeling.