Potential energy surface for the system: Application to the rotationally inelastic scattering of C2 in collisions with He

A new two-dimensional potential energy surface (2D-PES) for the interaction of He(1S) with the C 2 ( X 1 Σ g + ) molecule in its ground state is computed using multireference internally contracted configuration-interaction (MRCI) including Davidson correction (+Q) and the augmented correlation-consistent valence quadruple-zeta (aug-cc-pVQZ) basis set of Dunning. The C 2 ( X 1 Σ g + ) bond length was fixed at the experimental equilibrium distance. Rotationally inelastic scattering cross sections are computed using close-coupling (CC) method. The corresponding rate coefficients for the rotational transitions up to j = 20 are calculated for the temperatures 5 ⩽ T ⩽ 300 K.