ABSTRACT
Figure 1 0.7: Reflectivity spectrum of graphite from a face parallel to the l ayers (after Taft, 1 965) ,
Figure l IUI: Dispersion of the real (n) and imaginary (k) components of the refraction index of graphi te parallel (0 the hexagonal layers, as determined from the rer1ect ion spectrum off monocrystals (after Ergun et aI., 1 967) ,
1 5 1 4 1 3 1 2 Wavenumber x l O�1 (em-I )
2 0 K (cf. Fig. 1 0 . 1 0) . The narrow lines superposed onto the continuous curve have been attributed to vibronic replica (C=C bond at 1 400 cm-I ) . As will be seen in Section 1 0. 5 . 3 .4 , the position of this band, which is responsible for the luminescence of C60, is in very good agreement with the two-photons resonance observed on C60 films by third order optical harmonics generation (Kajzar et aI., 1 993 b ) .
