Which states produce Feshbach resonances in ultracold atom-molecule collisions?
In plain words
When ultracold atoms collide with ultracold molecules, the loss rate spikes at certain magnetic fields. Whether these spikes come from loosely bound long-range states or from the tangled short-range states of the three-atom complex is debated.
Precise statement
Collisions of ground-state bialkali molecules with atoms (for example NaK + K, NaLi + Na) show isolated magnetic Feshbach resonances (Yang et al., Science 2019). Determine whether their positions, widths and density arise from long-range states of the atom-molecule pair (Frye and Hutson, Phys. Rev. Research 2023) or from the dense, chaotic short-range spectrum of the triatomic complex. Answer: a model that predicts resonance positions for a new atom-molecule pair before measurement.
What would settle it
Advance prediction and subsequent measurement of resonance positions and widths in a previously unmeasured atom-molecule system.
Status in the literature
Frye and Hutson (2023, doi:10.1103/PhysRevResearch.5.023001) attributed observed resonances to long-range states; independent predictive tests are lacking.