Continuous coupling of ultracold atoms to an ionic plasma via Rydberg excitation

Abstract

We characterize the two-photon excitation of an ultracold gas of rubidium atoms to Rydberg states analyzing the induced atomic losses from an optical dipole trap. Extending the duration of the Rydberg excitation to several milliseconds, the ground-state atoms are continuously coupled to the formed positively charged plasma. In this regime we measure the $n$ dependence of the plasma-induced blockade effect and we characterize the interaction of the excited states and the ground state with the plasma. We also investigate the influence of the quasielectrostatic trapping potential on the system, confirming the validity of the ponderomotive model for states with $20\ensuremath{\le}n\ensuremath{\le}120$.