Ground-state configurations and unresolved transition arrays in extreme ultraviolet spectra of lanthanide ions

Theoretical ground-state configurations of lanthanide ions calculated with the Cowan suite of codes are presented. Theoretical $4d$-$4f$ and $4p$-$4d$ spectra of Pd-like to Rb-like lanthanide ions calculated using the relativistic flexible atomic code are also shown. The effects of configuration interaction are investigated, and the results compare favorably with experiments in which, for increasing nuclear charge, strong emission peaks are observed to move toward shorter wavelength. The application of these strong emitters as extreme ultraviolet radiation sources, a topic of emerging interest, is discussed.