Collisional excitation of CH(X²Π) by He: new ab initio potential energy surfaces and scattering calculations.

We present a new set of potential energy surfaces (PESs) for the CH(X(2)Π)-He van der Waals system. Ab initio calculations of the CH-He PES were carried out using the open-shell single- and double-excitation coupled cluster approach with non-iterative perturbational treatment of triple excitations [RCCSD(T)]. The augmented correlation-consistent polarized valence quadruple-zeta (aug-cc-pVQZ) basis set was employed augmented by mid-bond functions.