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Magneto-Optical Trapping of Aluminum Monofluoride

J. E. Padilla-Castillo1, J. Cai1, P. Agarwal1, P. Kukreja1, R. Thomas1, B. G. Sartakov1, S. Truppe2, G. Meijer1, and S. C. Wright1,*

  • *Contact author: sidwright@fhi-berlin.mpg.de
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Phys. Rev. Lett. 135, 243401 – Published 10 December, 2025

DOI: https://doi.org/10.1103/ksnd-9fyf

Abstract

Magneto-optical trapping of molecules has thus far been restricted to molecules with Σ2 electronic ground states. These species are chemically reactive and only support a simple laser cooling scheme from their first excited rotational level. Here, we demonstrate a magneto-optical trap (MOT) of aluminum monofluoride (AlF), a deeply bound and intrinsically stable diatomic molecule with a Σ+1 electronic ground state. The MOT operates on the strong A1Π←X1Σ+ transition near 227.5 nm, whose Q(J) lines are all rotationally closed. We demonstrate a MOT of about 6×104 molecules for the J=1 level of AlF, more than 104 molecules for J=2 and 3, and with no fundamental limit in going to higher rotational levels. Laser cooling and trapping of AlF is conceptually similar to the introduction of alkaline-earth atoms into cold atom physics, and is key to leveraging its spin-forbidden a3Π←X1Σ+ transition for precision spectroscopy and narrow-line cooling.

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Enlarging the Periodic Table of Laser-Cooled Molecules

Published 10 December, 2025

A class of molecules with two valence electrons has been laser cooled and trapped for the first time.

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Article Text

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Phys. Rev. Lett. 135, 243401– Published 10 December, 2025
  • Received 3 June 2025
  • Revised 19 September 2025
  • Accepted 17 October 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Open access publication funded by the Max Planck Society.

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