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Collisions between Ultracold Molecules and Atoms in a Magnetic Trap

Jurgilas, S. and Chakraborty, A. and Rich, C. J. H. and Caldwell, L. and Williams, H. J. and Fitch, N. J. and Sauer, B. E. and Frye, Matthew D. and Hutson, Jeremy M. and Tarbutt, M. R. (2021) 'Collisions between Ultracold Molecules and Atoms in a Magnetic Trap.', Physical review letters., 126 (15). p. 153401.


We prepare mixtures of ultracold CaF molecules and Rb atoms in a magnetic trap and study their inelastic collisions. When the atoms are prepared in the spin-stretched state and the molecules in the spin-stretched component of the first rotationally excited state, they collide inelastically with a rate coefficient k 2 = ( 6.6 ± 1.5 ) × 10 − 11     cm 3 / s at temperatures near 100     μ K . We attribute this to rotation-changing collisions. When the molecules are in the ground rotational state we see no inelastic loss and set an upper bound on the spin-relaxation rate coefficient of k 2 < 5.8 × 10 − 12     cm 3 / s with 95% confidence. We compare these measurements to the results of a single-channel loss model based on quantum defect theory. The comparison suggests a short-range loss parameter close to unity for rotationally excited molecules, but below 0.04 for molecules in the rotational ground state.

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Publisher statement:Reprinted with permission from the American Physical Society: Jurgilas, S., Chakraborty, A., Rich, C. J. H., Caldwell, L., Williams, H. J., Fitch, N. J., Sauer, B. E., Frye, Matthew D., Hutson, Jeremy M. & Tarbutt, M. R. (2021). Collisions between Ultracold Molecules and Atoms in a Magnetic Trap. Physical Review Letters 126(15): 153401. © (2021) by the American Physical Society. Readers may view, browse, and/or download material for temporary copying purposes only, provided these uses are for noncommercial personal purposes. Except as provided by law, this material may not be further reproduced, distributed, transmitted, modified, adapted, performed, displayed, published, or sold in whole or part, without prior written permission from the American Physical Society.
Date accepted:04 March 2021
Date deposited:30 September 2021
Date of first online publication:13 April 2021
Date first made open access:30 September 2021

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