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

Abstract

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 X ⁴[(4f ⁷)(6s ¹)]_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 X ⁹Σ that is assigned experimentally in the LS-coupling scheme. Similarly, the sevenfold degenerate first excited states are characterized as a ³[(4f ⁷)(6s ¹)]_Ω, corresponding to the experimentally assigned a ⁷Σ term. Dmitriev et al. observed three excited states Ω₂, Ω₁, and Ω₃ above a ⁷Σ term. The three calculated excited states, A ⁴[(4f ⁷)_1/2(6p ¹)_3/2 + …]₂, A ⁴[(4f ⁷)_−1/2(6p ¹)_3/2 + …]₁, and B ⁴[(4f ⁷)_5/2(6p ¹+5d ¹)_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.