Inner-shell photoabsorption of Fe14+: Unimportance of correlation and relativistic effects

We have performed a series of calculations of the photoabsorption cross section of Fe14+ near the 2p(-1) and 2s(-1) edges, within the framework of R-matrix theory. We find the unexpected result that the inclusion in the calculation of such effects as the spin-orbit interaction and higher-order correlations leads to a mere redistribution of flux among the various final channels, while the total convoluted photoabsorption cross section remains virtually unchanged. Hence, an appropriate minimal configuration LS coupling representation can adequately describe inner-shell total photoabsorption cross sections, leading to a saving in computational effort by orders of magnitude compared to more elaborate calculations.