The relativistic all-electron ab initio calculations on the multiplet electronic structure of U3+ ion

Abstract

The relativistic all-electron ab initio calculations have been performed on 5f3 manifold of free U3+ ion to explore the electronic structure and spectra. The spin-orbit-free low lying electronic states have been calculated at the level of theories of State-Averaged Complete Active Space Self-Consistent Field (SA-CASSCF) and Multi-State Complete Active Space Second-Order Perturbation (MS-CASPT2) using different sets of active orbitals. The corresponding spin-orbit states and the energy levels have been computed using Douglas-Kroll type of atomic mean-field integral (AMFI) approach. The ground state is 4I9/2 and the electron correlation has been found to be small in case of the excited 4I states. The low-lying energy levels obtained with the core-valence correlation effects in the treatment are in very good agreement with the experimental values.