Double-minimum 31Σ+u state in Rb2: Spectroscopic study and possible applications for cold-physics experiments

The double-minimum 3 1Σ+u state in 85 Rb 2and 85Rb87Rb was investigated by analyzing rotationally resolved spectra of the 3 1Σ+u⟵X1Σ+g band system simplified by polarization labeling. A total of 3665 transitions to rovibrational levels located in the inner well and above the internal barrier were identified and an accurate potential energy curve of the state reaching up to R≈21 Å was constructed using the inverted perturbation approach, making this state the best characterized double-minimum state in alkali dimers. The possibility of formation of ultracold rubidium dimers in the absolute ground state by photoassociation into levels of the 3 1Σ+u state above the internal barrier followed by spontaneous or stimulated emission is discussed.