The electronic spectrum of LuD

The electronic spectrum of LuD has been excited in a Lu 2 O 3 –Th–Cu hollow cathode filled with argon and traces of deuterium. All the recorded bands, lying in the visible region, belong to six electronic transitions towards the X 1 Σ + fundamental state of the molecule. Molecular constants and symmetry properties of these states have been deduced from the vibrational and rotational analyses. The electronic isotope shift has been obtained from data of the H → X system. Finally, the anomalous intensities observed in the Δν = 2 sequences of the E → X and G → X systems are explained in terms of a mutual interaction between pairs of vibrational levels belonging to the E and G states.