We have converted a quantum degenerate Fermi gas of 6Li atoms into an ultracold gas of 6Li2 molecules. This was accomplished by adiabatic passage through a narrow Feshbach resonance located at 543 G. The molecules are formed in the highest vibrational level which would normally be expected to quickly decay into molecules with lower vibrational energy, causing rapid heating and destruction of the ultracold gas. However, we have observed a remarkably long lifetime of ~1 s for the bare molecules . We emphasize that this measurement was made at a field far from the Feshbach resonance where the binding energy of the molecules greatly exceeds the Fermi energy. We observe the formation of a Bose-Einstein condensate of weakly bound molecules by tuning the field near the broad Feshbach resonance in 6Li (located at 838 G) and lowering the depth of the optical trap. It has become clear that bare molecules play an important role in resonant superfluidity. In order to better understand their importance we have developed a technique for directly imaging bare molecules using a bound-bound molecular transition. I will discuss our recent results.
1. K. E. Strecker, G. B. Partridge, and R. G. Hulet, Physical Review Letters 91, 080406 (2003).
Kevin Strecker, Guthrie Partridge, and Randall Hulet ~
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