The 1 S + 1 S asymptote of Sr 2 studied by Fourier - transform spectroscopy

An experimental study of the long range behavior of the ground state XΣ g of Sr2 is performed by high resolution spectroscopy of asymptotic vibrational levels and the use of available photoassociation data. Ground state levels as high as v′′ = 60 (outer turning point at 23 Å and 0.1 cm−1 below the asymptote) could be observed by Fourier-transform spectroscopy of fluorescence progressions induced by single frequency laser excitation of the v′ = 4, J ′ = 9 rovibrational level of the state 2Σ u . A precise value of the scattering length for the isotopologue Sr2 is derived and transferred to all other isotopic combinations by mass scaling with the given potential. The derived potential together with already published information about the state 2Σ u directs to promising optical paths for producing cold molecules in the electronic ground state from an ultracold ensemble of Sr atoms.