A spectroscopic study of resonant energy exchange among cold Rydberg atoms

Cold Rydberg atoms can exchange energy through long-range dipole-dipole interactions. The Stark effect allows us to tune the positions of the Rydberg states with a static electric field, which can bring into resonance this energy exchange. We present measurements of the spectrum of these resonant energy exchanges as the static field is varied for a broad range of initially excited Rydberg states and compare these measurements with calculated spectra.