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Nature 424, 47-50 (3 July 2003) | doi:10.1038/nature01738; Received 29 April 2003; Accepted 19 May 2003

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Creation of ultracold molecules from a Fermi gas of atoms

Cindy A. Regal1, Christopher Ticknor1, John L. Bohn1 & Deborah S. Jin2

  1. JILA, National Institute of Standards and Technology and Department of Physics, University of Colorado, Boulder, Colorado 80309-0440, USA
  2. Quantum Physics Division, National Institute of Standards and Technology, Boulder, Colorado 80309-0440, USA

Correspondence to: Cindy A. Regal1 Correspondence and requests for materials should be addressed to C.A.R. (Email: regal@jilau1.colorado.edu).

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Following the realization of Bose–Einstein condensates in atomic gases, an experimental challenge is the production of molecular gases in the quantum regime. A promising approach is to create the molecular gas directly from an ultracold atomic gas; for example, bosonic atoms in a Bose-Einstein condensate have been coupled to electronic ground-state molecules through photoassociation1 or a magnetic field Feshbach resonance2. The availability of atomic Fermi gases offers the prospect of coupling fermionic atoms to bosonic molecules, thus altering the quantum statistics of the system. Such a coupling would be closely related to the pairing mechanism in a fermionic superfluid, predicted to occur near a Feshbach resonance3, 4. Here we report the creation and quantitative characterization of ultracold 40K2 molecules. Starting with a quantum degenerate Fermi gas of atoms at a temperature of less than 150 nK, we scan the system over a Feshbach resonance to create adiabatically more than 250,000 trapped molecules; these can be converted back to atoms by reversing the scan. The small binding energy of the molecules is controlled by detuning the magnetic field away from the Feshbach resonance, and can be varied over a wide range. We directly detect these weakly bound molecules through their radio-frequency photodissociation spectra; these probe the molecular wavefunction, and yield binding energies that are consistent with theory.

  1. JILA, National Institute of Standards and Technology and Department of Physics, University of Colorado, Boulder, Colorado 80309-0440, USA
  2. Quantum Physics Division, National Institute of Standards and Technology, Boulder, Colorado 80309-0440, USA

Correspondence to: Cindy A. Regal1 Correspondence and requests for materials should be addressed to C.A.R. (Email: regal@jilau1.colorado.edu).