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

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 40K 87Rb + 87Rb. 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.

Automated summary

In this study, we examine the long-range states of complexes formed by alkali-metal diatomic molecules in a singlet state and alkali-metal atoms. We investigate the structure of the Hamiltonian for such systems and the interactions between the six angular momenta. We analyze the patterns and densities of the long-range states, as well as the Hamiltonian terms that can result in Feshbach resonances when the states cross threshold at varying magnetic fields. Using 40K 87Rb + 87Rb as a case study, we demonstrate multiple resonance types due to long-range states with rotational and/or hyperfine excitation, and discuss their likelihood at low to moderate magnetic fields.