Inner-shell photoionization of the 3dx ground state Fe ions

The total photoionization cross section for the 3d(x) ground state Fe ions, Fe III through Fe VIII, is calculated from the ionization threshold to the K edge including resonance features. The R-matrix method is used, the work being undertaken as part of the international RmaX ('R-matrix for x-ray processes') network. The dynamics of the photoionization process is illustrated by examining isonuclear trends and by quantifying some of the main resonance features due to inner-shell processes, particularly the large resonances arising from photoexcitation of the core (np(5)3d(x+1)) and the K edge. We also show that to calculate the cross section correctly through a deep inner-shell edge, requires the inclusion of states with inner-shell vacancies in all the preceding subshells.