The structure and transition probabilities of ionised Cr, Mn, Fe and Ni

The structure of the ions Cr-II-VI, Mn III-VI, Fe III-VI, and Ni III-VI was calculated ab initio. The relativistic corrections were included with the Breit-Pauli approximation and configuration interactions were partially included for those ions with a small number of 3d electrons. Transition probabilities were calculated for all lines in the transition arrays 3dsup(n) and 3dsup(n-1)4s to 3dsup(n-1)4p. A comparison of the calculated and observed energy structure allowed explicit estimates to be made for the total amount of configuration-interaction corrections to the energies and wavefunctions. The cumulative effect of many weakly interacting configurations dominates these corrections, causing an average mixing in the wavefunctions of from 1% to 20%. This mixing increases as the stage of ionisation decreases and as the number of outer electrons increases. The relativistic interactions are dominated by the spin-orbit term. The strength of the relativistic mixing is of the same order as the configuration mixing and it increases with increasing Z and increasing stage of ionisation. (author)