Observation of Chemical Reactions between a Trapped Ion and Ultracold Feshbach Dimers

TL;DR

This paper reports the observation of chemical reactions between a single trapped Yb+ ion and ultracold Li atoms with Li2 dimers, demonstrating a novel approach for creating cold molecular ions and detecting low-density molecular gases.

Contribution

It introduces a new experimental method to study ultracold ion-molecule reactions and models reaction rates based on dimer density and magnetic field effects.

Findings

Reaction rates follow Langevin rate predictions.

Detection sensitivity below 10^14 molecules per cubic meter.

Formation of LiYb+ molecular ions observed.

Abstract

We measure chemical reactions between a single trapped $^{174}$Yb$^+$ ion immersed in an ultracold bath of $^6$Li atoms containing trace amounts of Li$_2$ dimers. This produces LiYb$^+$ molecular ions that we detect via mass spectrometry. We explain the reaction rates by modelling the dimer density as a function of the magnetic field and obtain excellent agreement when we assume the reaction to follow the Langevin rate. Our results present a novel approach towards the creation of cold molecular ions and point to the exploration of ultracold chemistry in ion molecule collisions. What is more, with a detection sensitivity below molecule densities of $10^{14}\,\mathrm{m}^{-3}$, we provide a new method to detect low-density molecular gases.