K-shell photoabsorption and photoionization of trace elements. III. Isoelectronic sequences with electron number $19\leq N\leq 26$

TL;DR

This paper provides comprehensive K-shell photoabsorption and photoionization data for trace elements across specific isoelectronic sequences, enhancing atomic databases crucial for interpreting X-ray spectra from astrophysical sources.

Contribution

It completes the radiative datasets for elements with electron numbers 19 to 26 using advanced atomic structure calculations and compares different computational methods for accuracy.

Findings

Cross sections computed with BPRM for N=19 and 20 sequences show high accuracy.

AUTOSTRUCTURE in LS-coupling with damping effects is effective for N=21 to 26 sequences.

Relativistic corrections are necessary for accurate LS-coupling calculations.

Abstract

This is the final report of a three-paper series on the K-shell photoabsorption and photoionization of trace elements, namely F, Na, P, Cl, K, Sc, Ti, V, Cr, Mn, Co, Cu and Zn. K lines and edges from such elements are observed in the X-ray spectra of supernova remnants, galaxy clusters and accreting black holes and neutron stars, their diagnostic potential being limited by poor atomic data. We are completing the previously reported radiative datasets with new photoabsorption and photoionization cross sections for isoelectronic sequences with electron number $19\leq N\leq 26$. We are also giving attention to the access, integrity and usability of the whole resulting atomic database. Target representations are obtained with the atomic structure code AUTOSTRUCTURE. Where possible, cross sections for ground-configuration states are computed with the Breit--Pauli $R$-matrix method (BPRM) in either intermediate or $LS$ coupling including damping (radiative and Auger) effects; otherwise and more generally, they are generated in the isolated-resonance approximation with AUTOSTRUCTURE. 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 rest of the sequences ($21\leq N \leq 26$), AUTOSTRUCTURE was run in $LS$-coupling mode taking into account damping effects. Comparisons between these two methods for K-like Zn XII and Ca-like Zn XI show that, to ensure reasonable accuracy, the $LS$ calculations must be performed taking into account the non-fine-structure relativistic corrections.