Energy levels and oscillator strengths are calculated for the 3s23pn–3s23pn–13d transition arrays of Fe X, Fe XI, Fe XII and Fe XIII. The Slater radial integrals for these computations are adjusted so as to become consistent with established energy levels. Pertinent configuration interactions are included and the interaction integrals are reduced by up to 35% from values calculated ab initio, to achieve consistency.
Initial theroretical calculations are made using the ab initio Hartree-X, Slater-Condon programme of Cowan (1967, 1968), the second of which now includes configuration interaction. The first programme computes values for the average energy of the configuration Eav, the electrostatic direct integrals Fk and exchange integrals Gk , the spin-orbit parameters ζ, and the configuration interaction integrals Rk. From these the second programme computes energy levels, wavelengths and oscillator strengths for the transition arrays concerned.