Two-electron excitation of an interacting cold Rydberg gas

TL;DR

This paper investigates how interactions in a cold Rydberg gas of strontium atoms influence the excitation spectrum, revealing density-dependent electron collisions and plasma formation effects.

Contribution

It demonstrates the sensitivity of the Rydberg excitation spectrum to interactions and identifies electron-Rydberg collisions as the main transfer mechanism.

Findings

Density-dependent population transfer observed

Electron-Rydberg collisions cause l-changing transitions

Cold plasma formation linked to Rydberg interactions

Abstract

We report the creation of an interacting cold Rydberg gas of strontium atoms. We show that the excitation spectrum of the inner valence electron is sensitive to the interactions in the Rydberg gas, even though they are mediated by the outer Rydberg electron. By studying the evolution of this spectrum we observe density-dependent population transfer to a state of higher angular momentum l. We determine the fraction of Rydberg atoms transferred, and identify the dominant transfer mechanism to be l-changing electron-Rydberg collisions associated with the formation of a cold plasma.