Allowed transitions and intercombination lines in C III and C II

Systematic multiconfiguration Hartree-Fock results in the Breit-Pauli approximation are reported for the 2 s 2 1 S 0 → 2 s 2 p 3 P 1 intercombination line in C III and the 2 s 2 2 p 2 P -2 s 2 p 3 4 P multiplet in C II. Length and velocity forms of the oscillator strengths of related allowed transitions are also reported. The latter are used as a check on accuracy along with term energy separation and spin-orbit splitting. The predicted transition rate of 103 ± 3 s −1 for the intercombination line in C III lies outside the experimental error bars whereas the decay rates for C II are near the lower experimental limits.