Effective collision strengths for ground-state and 2s22p-2s2p2 fine-structure transitions in C II

Abstract

The ab initioR-matrix method is used to calculate effective collision strengths for electron-impact excitation of the boron-like ion C ii. We consider the fine-structure forbidden 2 Po1/2–2 Po3/2 transition within the 2s22p ground configuration as well as the 16 fine-structure transitions arising from excitation from the 2s22p to the 2s2p2 configuration. The 16 lowest LS target states are included in the calculation. Effective collision strengths are obtained by averaging the electron collision strengths over a Maxwellian distribution of electron velocities. Results are presented for electron temperatures in the range log T(K) = 3.0–5.5, appropriate for astrophysical applications. Good agreement with previous evaluations is obtained.