Configuration interaction effects in unresolved 5p⁶5d^N+1-5p⁵5d^N+2+5p⁶5d^N5f¹ transition arrays in ions Z = 79-92

Configuration interaction (CI) effects can greatly influence the way in which extreme ultraviolet (EUV) and soft X-ray (SXR) spectra of heavier ions are dominated by emission from unresolved transition arrays (UTAs), the most intense of which originate from Δn = 0, 4p⁶4d^N+1-4p⁵4d^N+2+4p⁶4d^N4f¹ transitions. Changing the principle quantum number n, from 4 to 5, changes the origin of the UTA from Δn = 0, 4p⁶4d^N+1-4p⁵4d^N+2+4p⁶4dN⁴f¹ to Δn = 0, 5p⁶5d^N+1-5p⁵5d^N+2+5p⁶5d^N5f¹ transitions. This causes unexpected and significant changes in the impact of configuration interaction from that observed in the heavily studied n = 4-n = 4 arrays. In this study, the properties of n = 5-n = 5 arrays have been investigated theoretically with the aid of Hartree-Fock with configuration interaction (HFCI) calculations. In addition to predicting the wavelengths and spectral details of the anticipated features, the calculations show that the effects of configuration interaction are quite different for the two different families of Δn = 0 transitions, a conclusion which is reinforced by comparison with experimental results.