We have observed resonant energy transfer between cold Rydberg atoms in spatially separated cylinders. Resonant dipole-dipole coupling excites the $49s$ atoms in one cylinder to the $49p$ state while the $41d$ atoms in the second cylinder are transferred down to the $42p$ state. We have measured the production of the $49p$ state as a function of separation of the cylinders ($0–80\mu \mathrm{m}$) and the interaction time ($0–25\mu \mathrm{s}$). In addition, we measured the width of the electric field resonances. A full many-body quantum calculation reproduces the main features of the experiments.

• Received 31 May 2007

DOI:https://doi.org/10.1103/PhysRevLett.100.243201