title: Spin-orbit configuration interaction study of the electronic structure of the 5f (2) manifold of U(4+) and the 5f manifold of U(5+).
abstract: The energy levels of the 5f configuration of U(5+) and 5f(2) configuration of U(4+) have been calculated in a dressed effective Hamiltonian relativistic spin-orbit configuration interaction framework. Electron correlation is treated in the scalar relativistic scheme with either the multistate multireference second-order multiconfigurational perturbation theory (MS-CASPT2) or with the multireference single and double configuration interaction (MRCI) and its size-extensive Davidson corrected variant. The CASPT2 method yields relative energies which are lower than those obtained with the MRCI method, the differences being the largest for the highest state (1)S(0) of the 5f(2) manifold. Both valence correlation effects and spin-orbit polarization of the outer-core orbitals are shown to be important. The satisfactory agreement of the results with experiments and four-component correlated calculations illustrates the relevance of dressed spin-orbit configuration interaction methods for spectroscopy studies of heavy elements.
authors.affiliation: Université de Sciences et Technologies de Lille 1, Laboratoire PhLAM, CNRS UMR 8523, CERLA, CNRS FR 2416, Bât P5, Villeneuve d'Ascq Cedex, France.
authors.forename: Cécile
authors.initials: C
authors.lastname: Danilo
authors.forename: Valérie
authors.initials: V
authors.lastname: Vallet
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Flament
authors.forename: Ulf
authors.initials: U
authors.lastname: Wahlgren