Inner-shell photoionization of the 3dxground 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 ( n p 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.