The role of atomic correlations in the theoretical study of minor actinide ions

This paper aims to demonstrate the recent possibilities to account for correlation and relativistic effects in studying the electronic structure and energy spectra of actinide ions. The fine structure of lowest term ⁷F of tetravalent curium (Cm⁴⁺) is considered as an example, as part of an ongoing project to understand the unexpected ground-state properties of this peculiar ion. The calculations were performed in multiconfiguration Hartree-Fock (including relativistic effects in the Breit-Pauli approach) and multiconfuguration Dirac-Fock approximations. The results obtained demonstrate that, whilst core-valence and core-core correlations are essential to assess correctly the Cm⁴⁺ term energy, their role in the determination of the fine structure is much less important compared to that of valence-valence correlations.