Long-range states and Feshbach resonances in collisions between ultracold alkali-metal diatomic molecules and atoms

TL;DR

This paper investigates the structure and behavior of long-range states and Feshbach resonances in ultracold alkali-metal diatomic molecules and atoms, focusing on their formation, interactions, and resonance patterns.

Contribution

It provides a detailed Hamiltonian analysis and case study of Feshbach resonances in a specific alkali-metal system, highlighting the types and likelihood of resonances at various magnetic fields.

Findings

Multiple types of Feshbach resonances due to long-range states were identified.

The study predicts the existence of resonances with rotational and hyperfine excitations at low to moderate magnetic fields.

The Hamiltonian analysis elucidates the couplings between angular momenta affecting resonance behavior.

Abstract

We consider the long-range states expected for complexes formed from an alkali-metal diatomic molecule in a singlet state and an alkali-metal atom. We explore the structure of the Hamiltonian for such systems, and the couplings between the six angular momenta that are present. We consider the patterns and densities of the long-range states, and the terms in the Hamiltonian that can cause Feshbach resonances when the states cross threshold as a function of magnetic field. We present a case study of $^{40}$K$^{87}$Rb+$^{87}$Rb. We show multiple types of resonance due to long-range states with rotational and/or hyperfine excitation, and consider the likelihood of them existing at low to moderate magnetic fields.