Production and characterization of crystalline 13C60

High-purity crystals of 99.1% 13C enriched C60 have been produced and their Raman and fluorescence spectra recorded together with those of C60 crystals containing the 13C isotope in natural abundance. The relative frequency shift of the intramolecular Raman-active modes is found to be determined by the square root of the averaged mass of the C60 molecules. From the observed blue-shift of the electronic origin of the fluorescence spectrum of C60 upon 12C → 13C substitution, it is concluded that the averaged intramolecular vibrational frequency of C60 decreases slightly upon electronic excitation.