Potential energy curve of the D(3)Î u1 state in rubidium dimer from spectroscopic measurements

•The D(3)Πu1 ← Σg+1 band system of Rb2 observed by polarization labelling spectroscopy.•The potential curve of the DΠu1 state constructed from experimental data.•The experimental potential curve used to test the quality of theoretical potentials.

The DΠu1 ← XΣg+1 band system in the Rb285 and 85Rb87Rb molecules has been investigated by the polarization labelling spectroscopy technique. The total of 2266 lines in this system were measured with an accuracy better than 0.1 cm−1. The resulting energies of the excited state levels (v=0-50,J=25-173) have been fitted to a Dunham polynomial expansion and directly to a numerical potential, providing the first experimental determination of the potential energy curve for the DΠu1 state. A good agreement is found between the experimental potential and those obtained from the most recent theoretical calculations.

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