AXISYMMETRICAL VIBRATIONAL-MODES OF FULLERENE-C-60

Axisymmetric vibrations for fullerene C60 are examined, naively modelling the molecule as a thin spherical shell. It is shown that the observed frequency pattern for the experimentally active Raman and i.r. modes reflects two branches, a(n) and b(n), of the fundamental, thin shell dispersion curve. There is satisfactory agreement between normalized frequencies calculated for a total of four Raman and four characteristic i.r. modes, and correspondingly strong resonances observed in practice. Six experimentally weaker, five-fold degenerate H(g) Raman active modes are not predicted. The four distinctly characteristic i.r. active, axisymmetric vibrations of the isolated C60 molecule are essentially preserved on crystallization into fcc fullerite, though a fundamental gap or potential i.r. ''window'' inherent to the model is not realized. The possible influence of Coriolis forces is briefly considered. The model, though simple, may have applications to the higher order symmetric fullerenes and, suitably modified as a solid sphere of constant density, to the more recently observed ''nested'' fullerenes.