K-shell photoabsorption and photoionization

Cross sections were computed with BPRM only for the K (N=19) and Ca (N=20) isoelectronic sequences, the latter in LS coupling. For the remaining sequences (21<=N<=26), AUTOSTRUCTURE was run in LS-coupling mode taking into account damping effects. Comparisons between these two methods for K-like ZnXII and Ca-like ZnXI show that to ensure reasonable accuracy, the LS calculations must be performed taking into account the non-fine-structure relativistic corrections.

The original data structures of the BPRM and AUTOSTRUCTURE output files, namely photoabsorption and total and partial photoionization cross sections, are maintained but supplemented with files detailing the target (N_T_-electron system, where N_T_=N-1) representations and photon states (N-electron system). We conclude that because of the large target size, the photoionization of ions with N>20 involving inner-shell excitations rapidly leads to untractable BPRM calculations, and is then more effectively treated in the isolated resonance approximation with AUTOSTRUCTURE.

This latter approximation by no means involves small calculations as Auger damping must be explicitly specified in the intricate decay routes.