  An analysis of the frequency-dependent scattering rate reveals signatures of
the superconducting gap as well as the pseudogap in high-T_c cuprates. These
features can be identified in the temperature-dependent spectral function
W(omega), inverted from the optical data of the optimally-doped Bi2212 using an
experimentally unambiguous method that shows the behavior of both the maxima
and minima in the spectral function.
