equipped with a liquid nitrogen cooled charge
couple device (CCD) detector, with a resolution better than
1 cm−1
. The excitation line, 514.5 nm, of an argon ion laser was
focused onto the sample using a ×100 MS Plan objective of an
Olympus Microscope BHSM, in a backscattering geometry. The
spectra were obtained with a measured power of about 10 mW on
the sample, during an integration time of 120 s, over the range
80–1200 cm−1
.