Production and Trapping of Cold Fermi-Gases

Eermions (particles with a spin of n ft/2 and n = odd integer) play an important role in many fields of physics, because aU stable elementary particles, such as electron, proton and neutron are Fermi particles with a spin of ft/2. Also atoms with a total angular momentum of n ft/2 (n = odd) are Fermions, such as the lithium isotope Li with a nuclear spin / = 1 ft and an electron spin s = ft/2, resulting in a total angular momentum of F = 3/2 ft or F = 1/2 ft. 

For Fermions the Pauli principle holds that any quantum state can be only occupied by at most one Fermion. Therefore a direct Bose-Einstein condensation of Fermions is not possible. However, two Fermions may couple to a Fermi-pair which is a Boson such as in supra-conductivity where two electrons couple to a Cooper pair and the condensation is realized by the Bosonic Fermi-pairs. Similar processes occur in supra-fluidity where two He atoms (Fermions) couple to a Boson. 

The question is now, whether such pairing can also happen for atoms in the gas phase, if the gas is cooled down to sufficiently low temperatures. The experimental possibilities of spectroscopic investigations of cold Fermi-pairs might elucidate many unclear aspects of supra-conductivity in solids or of supra-fluidity [1189]. 

The difference between Bose- and Fermi-gases becomes significant only at low temperatures when Bosons form a BEC, where all particles are in the lowest energy state while Fermions occupy all states up the Fermi energy. 

Most experiments for achieving cooling of Fermi gases have been performed with alkali atoms. There are only two stable Fermionic alkali isotopes namely Li and 

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