Fine-structure of excited atomic ions along potassium isoelectronic sequence

To perform theoretical calculations of electronic structures of high Z atomic ions, one has to consider the configuration mixings due to excitations and rearrangements of the core and valence electron orbitals with the same principal quantum number. We present a method to examine systematically such configuration mixings along isoelectronic sequences. As an illustrative example, such configuration mixings give rise to a reversed fine-structure splitting of 4 ²F_5/2,7/2 states for atomic ions with Z ≈ 36 along the potassium isoelectronic sequence; while the 5F, 6F, and 7F have normal fine-structure splittings.