R-MATRIX CALCULATIONS FOR ELECTRON-IMPACT EXCITATION OF FE-II - LS COUPLING AND BREIT-PAULI APPROXIMATIONS

Two sets of close coupling calculations have been carried out on the Cray-2 and the Cray Y-MP using the R-matrix method: (i) a 38-term calculation in LS coupling and (ii) a 41-level fine structure calculation in the Breit-Pauli approximation. The first set includes the quartet and sextet terms dominated by the configurations 3d(6)4s, 3d7 and 3d(6)4p and collision strengths are calculated for all 703 transitions in LS coupling. The second set of calculations is carried out using the Breit-Pauli version of the R-matrix method and includes a number of the important fine structure levels from the quartet and the sextet multiplets and 820 corresponding transitions. Detailed autoionization structures are obtained in both sets of collision strengths, and a significant enhancement is seen in the effective collision strengths for a number of transitions due to the resonances: for example, an enhancement of factors of 1.4, 2.5 and 1. 1 5 respectively for transitions from the 6D ground term to the lowest 4F, 4D and 4P terms.