  At the location of a magnetic-field Feshbach resonance, a mixture gas of
fermionic atoms and dimers of fermionic atom pairs is investigated in the
unitarity limit where the absolute value of the scattering length is much
larger than the mean distance between atoms. The dynamic equilibrium of the
mixture gases is characterized by the minimum of the Gibbs free energy. For the
fermionic atoms and dimers with divergent scattering length, it is found that
the fraction of the dimers based on a very simple theory agrees with the high
fraction of zero-momentum molecules observed in a recent experiment (M. W.
Zwierlein et al, Phys. Rev. Lett. 92, 120403 (2004)). The dimeric gas can be
also used to interpret the frequency of the radial breathing mode observed in
the experiment by J. Kinast et al (Phys. Rev. Lett. 92, 150402 (2004)).

Soft Condensed Matter;Statistical Mechanics