Observation of higher-order Raman modes inC60films

Raman spectra for oxygen-free solid ${\mathrm{C}}_{60}$ films were obtained at T=20 and 523 K. Using higher laser intensity at temperatures where photopolymerization is not important, over 100 Raman lines were observed and assigned to combination and overtone scattering from intramolecular vibrational modes and to otherwise Raman-inactive modes activated by isotopic substitution ${(}^{13}$ ${\mathrm{C}}^{12}$ ${\mathrm{C}}_{59}$). Values for nearly all of the silent mode frequencies are thereby obtained.