Analysis of the rotational and hyperfine structure in the ‘red’ bands of ruthenium monoxide (RuO)

Laser Induced Fluorescence has been used to study the spectroscopy of Ruthenium Monoxide (RuO) in the UNB laser-ablation molecular-jet apparatus. High-resolution spectra of six bands from four previously obtained electronic transitions, [16.05]5 – X⁵Δ₄, [16.19]4 - X⁵Δ₄, [16.19]4 - X⁵Δ₃ and [15.07]3 - X⁵Δ₄ plus two previously unobserved transitions, [15.70]3 and [16.36]3 – X⁵Δ₄, were obtained at a resolution 20 times higher than previous experiments. This enabled rotational structure of six individual RuO isotopologues, ⁹⁶RuO, ⁹⁹RuO, ¹⁰⁰RuO, ¹⁰¹RuO, ¹⁰²RuO and ¹⁰⁴RuO to be well resolved and was used to examine detailed rotational and vibrational isotope effects. Hyperfine structure due to the nuclear spin I = 5/2 of ⁹⁹Ru and ¹⁰¹Ru has also been well resolved and was a valuable aid in establishing the electron configurations of the electronic states. The difference in the hyperfine structure in the [16.05]5 and [16.19]4 states supported their assignment as the Ω = 5 and 4 spin orbit components, ⁵Φ₅ and ⁵Φ₄, of a single Hund's case (a) electronic state.