  Within the framework of the variational approach the ground state is studied
in a gas of Fermi atoms near the Feshbach resonance at negative scattering
length. The structure of the originating superfluid state is formed by two
coherently bound subsystems. One subsystem is that of quasi molecules in the
closed channel and the other is a system of pairs of atoms in the open channel.
The set of equations derived allows us to describe the properties of the ground
state at an arbitrary magnitude of the parameters. In particular, it allows one
to find a gap in the spectrum of single-particle Fermi excitations and sound
velocity characterizing a branch of collective Bose excitations.
