The ultraviolet emission spectrum of LaO

The ultraviolet emission spectrum of LaO, obtained under improved experimental conditions, has been reexamined. The high-resolution rotational analysis of the 0, 0 and 0, 1 F²Σ⁺ → X²Σ⁺ and 0, 0 D²Σ⁺ → X²Σ⁺ bands shows that the two excited electronic states F²Σ⁺ and D²Σ⁺ exhibit characteristic features of a b_βJ coupling scheme. A ligand field multiconfigurational calculation shows that these states arise mainly from the 7s and 8s configurations and gives theoretical support to the observed coupling case.