Controlling the nature of a charged impurity in a bath of Feshbach dimers

TL;DR

This paper models how a trapped ion interacts with ultracold Feshbach molecules, revealing a transition from dimer dissociation to molecular ion formation influenced by binding energy, collision energy, and trap fields, with potential applications in quantum technologies.

Contribution

It introduces a theoretical framework for controlling the formation of ultracold molecular ions via ion-molecule interactions in a Feshbach resonance environment.

Findings

Deeply bound dimers form molecular ions rapidly.

Kinetic energies of ions remain below 1 mK, ensuring trap confinement.

The formation rate approaches the Langevin collision rate.

Abstract

We theoretically study the dynamics of a trapped ion that is immersed in an ultracold gas of weakly bound atomic dimers created by a Feshbach resonance. Using quasi-classical simulations, we find a crossover from dimer dissociation to molecular ion formation depending on the binding energy of the dimers. The location of the crossover strongly depends on the collision energy and the time-dependent fields of the Paul trap. Deeply bound dimers lead to fast molecular ion formation, with rates approaching the Langevin collision rate $\Gamma'_\text{L}\approx4.8\times10^{-9}\,$cm$^3$s$^{-1}$. The kinetic energies of the created molecular ions have a median below $1\,$mK, such that they will stay confined in the ion trap. We conclude that interacting ions and Feshbach molecules may provide a novel approach towards the creation of ultracold molecular ions with applications in precision spectroscopy and quantum chemistry.