Ultra-long-range Rydberg molecules in a divalent atomic system

Abstract

We report the creation of ultra-long-range ${\mathrm{Sr}}_{2}$ molecules comprising one ground-state $5{s}^{2}$ ${}^{1}{S}_{0}$ atom and one atom in a $5sns$ ${}^{3}{S}_{1}$ Rydberg state for $n$ ranging from 29 to 36. Molecules are created in a trapped ultracold atomic gas using two-photon excitation near resonant with the $5s5p$ ${}^{3}{P}_{1}$ intermediate state, and their formation is detected through ground-state atom loss from the trap. The observed molecular binding energies are reproduced with the aid of first-order perturbation theory that utilizes a Fermi pseudopotential with effective $s$-wave and $p$-wave scattering lengths to describe the interaction between an excited Rydberg electron and a ground-state Sr atom.