  We present a practical method to compute the vibrational resonant Raman
spectra in solids with delocalized excitations. We apply this approach to the
study of tetrahedrous amorphous carbon. We determine the vibrational eigenmodes
and eigenvalues using density functional theory in the local density
approximation, and the Raman intensities using a tight binding approximation.
The computed spectra are in good agreement with the experimental ones measured
with visible and UV lasers. We analyze the Raman spectra in terms of
vibrational modes of microscopic units. We show that, at any frequency, the
spectra are dominated by the stretching vibrations. We identify a very rapid
inversion in the relative Raman intensities of the $sp^2$ and $sp^3$ carbon
sites with the frequency of the incident laser beam. In particular, the spectra
are dominated by $sp^2$ atoms below 4 eV and by $sp^3$ atoms above 6 eV.
