Many-Body Effects in a Frozen Rydberg Gas

Abstract

We studied the properties of a cold ( $\ensuremath{\sim}100\ensuremath{\mu}\mathrm{K}$) and dense ( $\ensuremath{\sim}{10}^{8--10}{\mathrm{cm}}^{\ensuremath{-}3}$) atomic Rydberg Cs gas, and found that the observed widths and shapes of resonances in population transfers cannot be explained in the framework of a usual gas model. We propose a ``frozen Rydberg gas'' model, where the interplay between two-body and many-body phenomena affects in an unexpected way the width and the shape of spectral lines.