# Tunable Feshbach resonances in collisions of ultracold molecules in $^2\Sigma$ states with alkali-metal atoms

## TL;DR

This paper investigates the potential for magnetically tunable Feshbach resonances in ultracold $^2\Sigma$ molecules and alkali-metal atoms, focusing on Rb+CaF, and explores their properties and controllability for molecule formation.

## Contribution

It provides the first detailed theoretical analysis of Feshbach resonances in ultracold $^2\Sigma$ molecules with alkali-metal atoms, highlighting their potential for controlling collisions and forming triatomic molecules.

## Key findings

- Resonances likely exist below 1000 G magnetic field.
- Resonances are broad enough for collision control and molecule formation.
- CaF rotation and anisotropy may produce additional resonances but do not prevent existing ones.

## Abstract

We consider the magnetically tunable Feshbach resonances that may exist in ultracold mixtures of molecules in $^2\Sigma$ states and alkali-metal atoms. We focus on Rb+CaF as a prototype system. There are likely to be Feshbach resonances analogous to those between pairs of alkali-metal atoms. We investigate the patterns of near-threshold states and the resonances that they cause, using coupled-channel calculations of the bound states and low-energy scattering on model interaction potentials. We explore the dependence of the properties on as-yet-unknown potential parameters. There is a high probability that resonances will exist at magnetic fields below 1000 G, and that these will be broad enough to control collisions and form triatomic molecules by magnetoassociation. We consider the effect of CaF rotation and potential anisotropy, and conclude that they may produce additional resonances but should not affect the existence of rotation-free resonances.