Ultracold Fermi Gas
Atom/molecule conversion in ultracold gases. The blue lines show the
energy of a pair of atoms that is magnetically tuned through a "resonance,"
corresponding to a bound vibrational level of the diatomic molecule.
This is an example of a "Feshbach resonance" that can be used
to vary the mean-field interaction energy of the atoms. The energy levels
actually anti-cross, as shown by the yellow lines, owing to a hyperfine
interaction. By preparing a gas of ultracold 6Li atoms at a field above
the crossing, and then adiabatically ramping the field (changing the
B field without any gain or loss of energy) through the crossing as
indicated by the green arrow, the atoms are converted into diatomic
molecules, Li2. Being composites of two fermions, these molecules are
Reported by: Strecker
et al., Physical Review Letters, 22 August 2003.
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