We report on the production of a pure sample of up to $3\times {10}^5$ optically trapped molecules from a Fermi gas of ${}^6\mathrm{L}\mathrm{i}$ atoms. The dimers are formed by three-body recombination near a Feshbach resonance. For purification, a Stern-Gerlach selection technique is used that efficiently removes all trapped atoms from the atom-molecule mixture. The behavior of the purified molecular sample shows a striking dependence on the applied magnetic field. For very weakly bound molecules near the Feshbach resonance, the gas exhibits a remarkable stability with respect to collisional decay.

• Received 5 August 2003

DOI:https://doi.org/10.1103/PhysRevLett.91.240402