  We study the dynamic structure factor for density and spin within the
crossover from BCS superfluidity of atomic fermions to the Bose-Einstein
condensation of molecules. Both structure factors are experimentally accessible
via Bragg spectroscopy, and allow for the identification of the pairing
mechanism: the spin structure factor allows for the determination of the two
particle gap, while the collective sound mode in the density structure reveals
the superfluid state.
