Back and Forth Transfer and Coherent Coupling in a Cold Rydberg Dipole Gas

Abstract

Coupling by the resonant dipole-dipole energy transfer between cold cesium Rydberg atoms is investigated using time-resolved narrow-band deexcitation spectroscopy. This technique combines the advantage of efficient Rydberg excitation with high-resolution spectroscopy at variable interaction times. Dipole-dipole interaction is observed spectroscopically as avoided level crossing. The coherent character of the process is linked to back and forth transfer in the $np+np⟷ns+(n+1)s$ reaction. Decoherence in the ensemble has two different origins: the atom motion induced by dipole-dipole interaction and the migration of the $s$-Rydberg excitation in the environment of $p$-Rydberg atoms.