Controlling Rydberg atom excitations in dense background gases

TL;DR

This paper investigates how dense background gases affect Rydberg atom spectra, combining historical theory, experimental measurements in different atomic clouds, and models to understand density shifts and localization effects.

Contribution

It introduces a microscopic model for density shifts considering perturber configurations and demonstrates localization of Rydberg excitations based on density shifts at high principal quantum numbers.

Findings

Measured density shifts in BEC and thermal clouds across various densities.

Compared experimental shifts with mean-field theoretical predictions.

Showed the potential to localize Rydberg excitations within specific density shells.

Abstract

We discuss the density shift and broadening of Rydberg spectra measured in cold, dense atom clouds in the context of Rydberg atom spectroscopy done at room temperature, dating back to the experiments of Amaldi and Segr\`e in 1934. We discuss the theory first developed in 1934 by Fermi to model the mean-field density shift and subsequent developments of the theoretical understanding since then. In particular, we present a model whereby the density shift is calculated using a microscopic model in which the configurations of the perturber atoms within the Rydberg orbit are considered. We present spectroscopic measurements of a Rydberg atom, taken in a Bose-Einstein condensate (BEC) and thermal clouds with densities varying from $5\times10^{14}\textrm{cm}^{-3}$ to $9\times10^{12}\textrm{cm}^{-3}$. The density shift measured via the spectrum's center of gravity is compared with the mean-field energy shift expected for the effective atom cloud density determined via a time of flight image. Lastly, we present calculations and data demonstrating the ability of localizing the Rydberg excitation via the density shift within a particular density shell for high principal quantum numbers.