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 ${}^{40}\mathrm{K}{}^{87}\mathrm{Rb}+{}^{87}\mathrm{Rb}$. 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.

• Received 15 December 2022
• Accepted 6 March 2023

DOI:https://doi.org/10.1103/PhysRevResearch.5.023001

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Published by the American Physical Society