Precision laser spectroscopy of strontium dimers*

Laser spectroscopy of molecules offers the intriguing prospect of constraining mass-dependent forces at the nanometer length scale, where current state-of-the-art limits are held by neutron scattering experiments. In this context, homonuclear alkaline-earth dimers are an attractive species, possessing naturally narrow transitions in the form of molecular subradiance, infrared inactive vibrational ground states, and spin-forbidden triplet electronic states. In addition, the ¹Σ ground potentials of alkaline-earth dimers are well amenable to quantum chemistry modeling. Recently we have mapped out all 63 vibrational states with J=0 and J=2 belonging to X¹Σ_g⁺ in ⁸⁸Sr₂, and we compare the binding energies to ab initio calculations. We demonstrate how light shifts induced by the optical lattice trap on a vibrational Raman clock transition can be used to accurately determine molecular polarizability ratios and transition strengths. We also discuss ongoing efforts toward characterizing the instability and systematic shifts of the molecular clock.