Molecular BEC interference

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© C. Kohstall & R. Grimm.

An atom of 6Li is a fermion, with three electrons, three protons, and three neutrons adding together for a total of nine spin-1/2 particles. It's possible to make a degenerate Fermi gas of 6Li by cooling the atoms in a trap together with bosonic 7Li. To make a BEC out of the Fermi gas, it's necessary to make the fermionic atoms pair up and form bosons. Researchers in Innsbruck accomplished this by using a carefully tuned laser to induce individual 6Li atoms to form diatomic molecules of 6Li2. Unlike their fermion parents, these bosonic molecules are in identical macroscopic quantum states, and thus form a BEC. When two such clouds overlap, macroscopic interference patterns (compare to Figure 26) immediately appear showing both that pairing of fermions creates bosons, and that these have condensed into coherent matter-wave clouds. (Unit: 6)