Electronic transitions of ruthenium monoxide.

The electronic transition spectrum of ruthenium monoxide (RuO) molecule in the spectral region between 545 nm to 640 nm has been recorded and analyzed using laser ablation/reaction free-jet expansion and laser induced fluorescence spectroscopy. The RuO molecule was produced by reacting laser-ablated ruthenium atoms with N2O seeded in argon. Nine vibrational bands were recorded, and they are identified to belong to four electronic transition systems, namely, the [18.1]Ω = 4-X(5)Δ4, [16.0]Ω = 5-X(5)Δ4, [18.1]Ω = 3-X(5)Δ3, and [15.8]Ω = 4-X(5)Δ3 systems. RuO was determined to have a X(5)Δ4 ground state. A least-squares fit of the measured rotational lines yielded molecular constants for the ground and the low-lying electronic states. A molecular orbital energy level diagram has been used to help with the assignment of the observed electronic states.