Ionization in a frozen Rydberg gas with attractive or repulsive potentials

TL;DR

This study demonstrates how dipole-dipole interactions influence Penning ionization in a frozen Rydberg gas, showing that the nature of the potential (attractive or repulsive) affects ionization and plasma formation.

Contribution

It provides experimental evidence on the role of dipole-dipole interactions in ionization processes within Rydberg gases, highlighting the impact of potential type on ionization suppression or occurrence.

Findings

Penning ionization is suppressed for repulsive potentials (n<42).

Ionization occurs for attractive potentials (n>42).

Blackbody radiation significantly contributes to initial ionization.

Abstract

We report clear evidence of the role of dipole-dipole interaction in Penning ionization of Rydberg atoms, leading to the formation of an ultracold plasma. Penning ionization of np Rydberg Cesium atoms is prevented for states with in n < 42, which correspond to a repulsive potential, but it does not occur for n larger than 42, corresponding to an attractive potential. Blackbody radiation is mostly responsible for the background and initial ionization, although ion-Rydberg collisions and population transfer due to limited superradiance may have to be considered.