SCATTERING OF THE VIBRATIONAL FREQUENCIES OF C-13(X)C-12(60-X). - A RAMAN-SPECTROSCOPY AND QUANTUM-CHEMICAL STUDY

Through a joint experimental and theoretical study we assess the effec t of random C-13 substitution in the vibrational spectra of (C60-xCx)C -12-C-13 First, Raman data are gathered for a 25% C-13-substituted sam ple. Then, we randomly generate an ensemble of isotopomers of (C60-xCx )-C-12-C-13, with x= 18, 36. For all these isotopomers we calculate th e vibrational frequencies and normal modes and project them onto the s pace of the normal modes of (C60)-C-12 to yield mode scrambling matric es. The accumulation of the resulting mode scrambling matrices gives t he frequency dispersion upon random isotopic substitution. Both experi ment and theory find that the dispersion of the lower-frequency vibrat ion is multimodal.