Excitation of the fine-structure transition of C+in collisions with molecular hydrogen

Results are presented of quantum-mechanical calculations of the cross section for excitation of the fine-structure transition (2p 2 P 1 2/ 0 - 2 P 3 2/ 0 ) of C + by H 2 . Results published by Chu and Dalgarno (1975), relating to a collinear C + -H-H collision, are shown to be underestimates at low energies, where orbiting occurs if the orientation of the H-H internuclear axis is not assumed to be restricted during the collision.