Isotopic and isomeric effects in high-pressure hydrogenated fullerenes studied by Raman spectroscopy

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Raman spectra of hydro- and deuterofullerenes, C 60H 36 and C 60D 36, prepared under hydrogen or deuterium pressure of 3.0 GPa at different conditions of temperature and hydrogenation time, have been measured at room temperature and normal pressure. Spatially resolved micro-Raman study shows that the homogeneity and optical properties of the samples depend primarily on the synthesis temperature. The Raman spectrum of hydrofullerene contains a large number of prominent peaks originating from the various isomers. The comparison of the experimental data with results of molecular dynamics calculations shows that various isomers are present in the samples, with the most abundant of them being the ones with symmetries S 6, T and D 3d. The Raman spectrum of the deuterofullerene is similar in structure to that of the hydrofullerene, however, significant differences occur in the frequency positions of the C–H and C–D stretching and bending modes which are expected from the isotopic effect. In particular, the isotopic shift ratio for the stretching mode, Ω H /Ω D ≈1.32 , is smaller than the expected one from the mass ratio for pure C–H and C–D stretching modes.