The detection and characterization of the visible emission spectra of lutetium monochloride, monobromide, and monoiodide

Molecular emission has been observed in high pressure electrodeless microwave arc discharges from the monochloride, monobromide, and monoiodide of lutetium. The vibrational analyses of two electronic transitions in LuCl, LuBr, and LuI represent the first spectroscopic data for these molecules. The Lu monohalide band spectra in the visible are composed of two electronic transitions, which are degraded to the red. These transitions are characterized by long vibrational sequences, centered about Δv =0. The term values for LuBr and LuI are shifted to the red with respect to LuCl by ∼1000 and ∼2500 cm−1, respectively, for both transitions. The vibrational analyses reveal that both the upper and lower state vibrational frequencies of these two transitions are different for all three monohalides. This suggests that four different electronic states are involved in these two transitions. Explanations for these two transitions are sought by analogy with the group III (Sc, Y, and La) monohalides and the isoelectronic molecules ZrO and HfO. A comparison has been made between the vibrational frequencies of the Lu and Yb monohalides.