Lifetimes of ultralong-range strontium Rydberg molecules in a dense BEC

TL;DR

This study investigates the lifetimes and decay mechanisms of ultralong-range strontium Rydberg molecules in a dense BEC, revealing decay processes and setting limits on coherence times for experiments involving Rydberg states in cold gases.

Contribution

It provides the first detailed measurement of Rydberg molecule lifetimes in a dense BEC and identifies dominant decay channels, advancing understanding of Rydberg interactions in many-body systems.

Findings

Lifetimes of 1-5 microseconds for Rydberg molecules.

Main decay channels include associative ionization and L-changing collisions.

Decay rates align with a model of core ion and ground-state atom interactions.

Abstract

The lifetimes and decay channels of ultralong-range Rydberg molecules created in a dense BEC are examined by monitoring the time evolution of the Rydberg population using field ionization. Studies of molecules with values of principal quantum number, $n$, in the range $n=49$ to $n=72$ that contain tens to hundreds of ground state atoms within the Rydberg electron orbit show that their presence leads to marked changes in the field ionization characteristics. The Rydberg molecules have lifetimes of $\sim1-5\,\mu$s, their destruction being attributed to two main processes: formation of Sr$^+_2$ ions through associative ionization, and dissociation induced through $L$-changing collisions. The observed loss rates are consistent with a reaction model that emphasizes the interaction between the Rydberg core ion and its nearest neighbor ground-state atom. The measured lifetimes place strict limits on the time scales over which studies involving Rydberg species in cold, dense atomic gases can be undertaken and limit the coherence times for such measurements.