Fine-Structure Excitation of Singly-Ionized Carbon Atom by Collision with Helium Atom

The 2 P 1/2 → 2 P 3/2 excitation cross section of C + in low energy collision with He is calculated with the close-coupling method. A pseudo-potential is used to calculate the repulsive interaction due to the electron cloud overlap between the colliding atoms. In low-energy region the cross section shows oscillatory structures which come from a shape resonance caused by the centrifugal barrier. The magnitude of the excitation cross section is a few times smaller than that for the C + –H collision. An estimate of the cross section of the same excitation in C + –H 2 collision is also given.