The multiplet electronic structure of UO+ ion: Relativistic two-component ab initio approach.

• The bond lengths in case of excited states are close to that of the ground state. • The rotational constants for higher states are nearer their corresponding experimental values. • The energy levels of 4I spin-orbit states of U3+ ion are not affected much in the presence of oxide ion in UO+. The relativistic two-component ab initio calculations have been carried out to calculate the electronic structure and spectroscopic properties of UO+ ion. The State-Averaged Restricted Active Space Self-Consistent Field (SA-RASSCF) calculations have been performed with spin-orbit effects. The ground state along with a manifold of low-lying spin-orbit states below 12 600 cm−1 have been reported and compared with available results from experiment, Ligand Field Theory (LFT) and previous theoretical results. The configurational assignments along with spectroscopic properties at equilibrium bond distances and also the nature of the potential energy curves have been reported. The ground state Ω = 9/2 at R = 1.790 Å is found to be ionic in nature, U3+(5 f 3(4I))O2−(1S), with a vibrational frequency of 962 cm−1. The computed excitation energies compare reasonably well with the available experimental counterpart. [ABSTRACT FROM AUTHOR]