Van der Waals explosion of cold Rydberg clusters

TL;DR

This paper experimentally observes how van der Waals forces cause Rydberg atom clusters to expand, providing real-space measurements that match numerical simulations of the explosion process.

Contribution

First direct real-space measurement of van der Waals forces affecting Rydberg atom clusters, validating theoretical models with experimental data.

Findings

Measured Rydberg cluster expansion due to van der Waals forces

Experimental results agree with numerical simulations

Demonstrated controlled creation and expansion of Rydberg clusters

Abstract

We report on the direct measurement in real space of the effect of the van der Waals forces between individual Rydberg atoms on their external degrees of freedom. Clusters of Rydberg atoms with inter-particle distances of around 5 {\mu}m are created by first generating a small number of seed excitations in a magneto-optical trap, followed by off-resonant excitation that leads to a chain of facilitated excitation events. After a variable expansion time the Rydberg atoms are field ionized, and from the arrival time distributions the size of the Rydberg cluster after expansion is calculated. Our experimental results agree well with a numerical simulation of the van der Waals explosion.