  Raman scattering studies have been performed on underdoped
Bi2Sr2CaCu2O8+delta. In single crystals underdoped by oxygen removal, a 590
cm-1 peak is observed in the B1g spectrum. The feature is observed to soften in
frequency by 3.8% with isotopic exchange for 16-O by 18-O. In contrast, the
590cm-1 peak is not observed in crystals underdoped by Y substitution which
suggests that it correspond to a disorder induced vibrational mode. We have
also found that underdoping leads to a depletion of low energy spectral weight
from regions of the Fermi surface located near the Brillouin zone axes.
