Relativistic MR-MP Energy Levels for L-shell Ions of Iron

A comprehensive set of level energies is provided for the valence and K-vacancy states of the ions Fe xvii , Fe xviii , Fe xix , Fe xx , Fe xxi , Fe xxii , Fe xxiii , and Fe xxiv . Level energies were calculated with the relativistic Multi-Reference Møller–Plesset Perturbation Theory method (MR-MP). The data set includes level energies coming from the configurations , , , , , and , where 1 ≤ q ≤ 8, n ≤ 5, and l ≤ 3. The results have been compared with data from the National Institute of Standards and Technology (NIST) online database and with previous calculations. In general, the deviation from the NIST-recommended values is below 0.6 and 1.0 eV for valence and K-vacancy level energies, respectively. However, we identify numerous outliers among the NIST-recommended values. The extensive data set presented here greatly augments the amount of available reference level energies in the NIST database for L-shell ions of Fe, and we expect our data set to ease line identification and confirm level designations.