Measurements of the transition dipole moments for the $5\mathrm{s}5\mathrm{p}\, ^3\textrm{P}_1$-$5\mathrm{s}n\mathrm{s}\, ^3\textrm{S}_1$ transitions via Autler-Townes spectroscopy

Abstract We report on experimental measurements of the transition dipole moments (TDMs) between the intermediate state $5\mathrm{s}5\mathrm{p}\, ^3\textrm{P}_1$ and the triplet Rydberg series $5\mathrm{s}n\mathrm{s}\, ^3\textrm{S}_1$ in an ultracold strontium gas. Here $n$ is the principal quantum number ranging from 19 to 40. The transition $5\mathrm{s}5\mathrm{p}\, ^3\textrm{P}_1$ − $5\mathrm{s}n\mathrm{s}\, ^3\textrm{S}_1$ is coupled via an UV beam, inducing Autler-Townes splitting of both states. Such a splitting of the intermediate state is spectroscopically measured using absorption imaging on a narrow transition $5\mathrm{s}^2\, ^1\textrm{S}_0$ − $5\mathrm{s}5\mathrm{p}\, ^3\textrm{P}_1$ in an ultracold gas of strontium atoms. The power and size of the UV beam are carefully determined, with which the TDMs are extracted from the measured Autler-Townes splitting. The experimentally obtained TDMs are compared to calculations based on a parametric core potential, on a Coulomb potential with quantum defect, and on the open-source library Alkali Ryderg Calculator (ARC), finding good agreement with the former two models and significant deviation with the latter.