Electron impact excitation of n=3 states of C III: An application of a new R-matrix package

The R-matrix method is used to obtain effective collision strengths for the beryllium-like ion C III for all transitions between the six n=2 states with configurations 2s2, 2s2p and 2p2 and the six n=3 states with configurations 2s3s, 2s3p and 2s3d. In addition effective collision strengths between all pairs of these n=3 states are calculated. The calculations are carried out including the first twelve target eigenstates in the R-matrix expansion of the total wavefunction. In order to obtain converged cross sections involving the n=3 states a new no-exchange R-matrix package was developed and is described in this paper. This package, combined with the Burgess sum rule, is used to determine the high partial wave contributions, to the cross section. Results for the effective collision strengths are presented in tabular form for temperatures in the range 104-105.8 K.