Observation of magnetically tunable Feshbach resonances in ultracold 23Na40K + 40K collisions

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Science  18 Jan 2019:
Vol. 363, Issue 6424, pp. 261-264
DOI: 10.1126/science.aau5322

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Brief get-togethers between NaK and K

Cooling molecules to nanokelvin temperatures places them under the tightest quantum mechanical constraints. Studies in this intriguing regime have been limited to diatomics: Two cold atoms can be lured together into weakly associated Feshbach resonances, which lasers can then shift into a more stable molecular state. Yang et al. now report the observation of triatomic Feshbach resonances in ultracold collisions between potassium (K) atoms and sodium potassium (NaK) diatomics. The findings potentially set the stage for the preparation and study of ultracold triatomic molecules.

Science, this issue p. 261


Resonances in ultracold collisions involving heavy molecules are difficult to simulate theoretically and have proven challenging to detect. Here we report the observation of magnetically tunable Feshbach resonances in ultracold collisions between potassium-40 (40K) atoms and sodium-23–potassium-40 (23Na40K) molecules in the rovibrational ground state. We prepare the atoms and molecules in various hyperfine levels of their ground states and observe the loss of molecules as a function of the magnetic field. The atom-molecule Feshbach resonances are identified by observing an enhancement of the loss. We have observed 11 resonances in the magnetic field range of 43 to 120 gauss. The observed atom-molecule Feshbach resonances at ultralow temperatures probe the three-body potential energy surface with exceptional resolution and will help to improve understanding of ultracold collisions.

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