Improved characterization of Feshbach resonances and interaction potentials between $^{23}$Na and $^{87}$Rb atoms

TL;DR

This paper refines the understanding of Feshbach resonances between sodium-23 and rubidium-87 atoms, improving potential models and mapping magnetic fields to scattering lengths, crucial for ultracold molecule research.

Contribution

It provides an improved characterization of a key Feshbach resonance, refines interaction potentials, and identifies additional resonances in Na-Rb mixtures using experimental and coupled-channel calculations.

Findings

Refined singlet and triplet potential energy curves.

High-precision magnetic field to scattering length mapping.

Identification of 10 new s-wave Feshbach resonances.

Abstract

The ultracold mixture of \Na and \Rb atoms has become an important system for investigating physics in Bose-Bose atomic mixtures and for forming ultracold ground-state polar molecules. In this work, we provide an improved characterization of the most commonly used Feshbach resonance near 347.64 G between \Na and \Rb in their absolute ground states. We form Feshbach molecules using this resonance and measure their binding energies by dissociating them via magnetic field modulation. We use the binding energies to refine the singlet and triplet potential energy curves, using coupled-channel bound-state calculations. We then use coupled-channel scattering calculations on the resulting potentials to produce a high-precision mapping between magnetic field and scattering length. We also observe 10 additional $s$-wave Feshbach resonances for \Na and \Rb in different combinations of Zeeman sublevels of the $F = 1$ hyperfine states. Some of the resonances show 2-body inelastic decay due to spin exchange. We compare the resonance properties with coupled-channel scattering calculations that full take account of inelastic properties.