Electronic spectra of EuF studied by a four-component relativistic configuration interaction method

The electronic structure of the EuF molecule is investigated using a four-component relativistic general open-shell configuration interaction method. All low-lying excited states below 3.0 eV are characterized by applying the f-shell Omega decomposition method, which was proposed by the present authors to analyze the electronic spectra of GdF. The ground states are ninefold degenerate and are expressed in the present terminology as X4[(4f7)(6s1)]Ω. The superscript (4) here denotes the maximum Ω value. The electronic angular momentum projected onto the molecular axis (Ω) runs from 4 to −4, and the electronic configuration is represented symbolically by the gross atomic orbital populations of the Eu moiety (4f)7(6s)1. These features are consistent with the term X9Σ that is assigned experimentally in the LS-coupling scheme. Similarly, the sevenfold degenerate first excited states are characterized as a3[(4f7)(6s1)]Ω, corresponding to the experimentally assigned a7Σ term. Dmitriev et al. observed three excited states Ω2, Ω1, and Ω3 above a7Σ term. The three calculated excited states, A4[(4f 7)1/2(6p1)3/2 + …]2, A4[(4f 7)−1/2(6p1)3/2 + …]1, and B4[(4f 7)5/2(6p1+5d1)1/2 + …]3, are, respectively, the most plausible identifications of the Ω2, Ω1, and Ω3 given by Dmitriev et al. These three states have large oscillator strengths with the X and a families.