A theoretical investigation of photoabsorption and photoionization of Fe${}^{14+}$ extending beyond an earlier frame transformation $R$-matrix implementation is performed using a fully correlated, Breit-Pauli $R$-matrix formulation including both fine-structure splitting of strongly bound resonances and radiation damping. The radiation damping of $2p\to nd$ resonances gives rise to a resonant photoionization cross section that is significantly lower than the total photoabsorption cross section. Furthermore, the radiation-damped photoionization cross section is found to be in good agreement with recent experimental results once a global shift in energy of $\approx$–3.5 eV is applied. These findings have important implications. First, the presently available synchrotron experimental data are applicable only to photoionization processes and not to photoabsorption; the latter is required in opacity calculations. Second, our computed cross section, for which the $L$-shell ionization threshold is aligned with the NIST value, shows a series of $2p\to nd$ Rydberg resonances that are uniformly 3–4 eV higher in energy than the corresponding experimental profiles, suggesting that the actual $L$-shell threshold energy is lower than the value obtained using the current NIST data.

• Received 21 February 2012

DOI:https://doi.org/10.1103/PhysRevA.85.040701