  The electronic Raman scattering has been investigated in optimally oxygen
doped YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ single crystals as well as in crystals
with non-magnetic, Zn, and magnetic, Ni, impurities. We found that the
intensity of the A$_{1g}$ peak is impurity independent and their energy to
$T_{c}$ ratio is almost constant ($2\Delta/k_{B}T_{c}\sim5$). Moreover, the
signal at the B$_{1g}$ channel is completely smeared out when non-magnetic Zn
impurities are present. These results are qualitatively interpreted in terms of
the Zeyher and Greco's theory that relates the electronic Raman scattering in
the A$_{1g}$ and B$_{1g}$ channels to \textit{d}-CDW and superconducting order
parameters fluctuations, respectively.
