We perform two-photon photoassociation spectroscopy of the heteronuclear CsYb molecule to measure the binding energies of near-threshold vibrational levels of the $X{}^2{\mathrm{\Sigma }}_{1/2}^{+}$ molecular ground state. We report results for ${}^{133}\mathrm{Cs}{}^{170}\mathrm{Yb}$, ${}^{133}\mathrm{Cs}{}^{173}\mathrm{Yb}$, and ${}^{133}\mathrm{Cs}{}^{174}\mathrm{Yb}$, in each case determining the energy of several vibrational levels including the least-bound state. We fit an interaction potential based on electronic structure calculations to the binding energies for all three isotopologs and find that the ground-state potential supports 77 vibrational levels. We use the fitted potential to predict the interspecies $s$-wave scattering lengths for all seven Cs+Yb isotopic mixtures.

• Received 1 June 2018

DOI:https://doi.org/10.1103/PhysRevA.98.022707