Photoionization of inner shells of the Mg and Ar isonuclear sequences

Calculations of the photoionization cross sections of inner shells of Mg, Mg²⁺, and Mg⁸⁺ along with Ar, Ar⁶⁺, and Ar⁸⁺ have been performed at the relativistic-random-phase approximation level. The results confirm earlier predictions made using the simple Hartree-Slater model that removal of outer-shell electrons does not affect the photoionization cross sections of inner-shell electrons, except for a shift of threshold.