Improved RCI techniques for treating 4fn atoms and ions: Application to Gd IV energies

Abstract

Relativistic configuration interaction results for energy levels and Landé g-values of Gd IV 4f7 J = 7/2 and Gd IV 4f6 5d J = 5/2, 7/2, 9/2, and energies of 51 new levels are presented. The average error between adjacent energy levels in 4f7 is 4.5%. Significant improvements in computational efficiency and accuracy for the difficult-to-treat 4f7 and 4f6 5d states are introduced, including the use of ab initio determined shifts of diagonal matrix elements (ME) for 4f6 parents, neglecting off-diagonal MEs between quadruple (triple) excitations, and a more systematic treatment of radial convergence.PACS Nos.: 31.15.am, 31.15.vj