Magnetic properties of C_{60} and C_{70}

The published C-13 NMR spectra of C60 give an absolute carbon shielding of sigma = 43 ppm, i.e. 14 ppm less than for carbon in benzene. Extrapolation from ab initio coupled Hartree-Fock calculations with the origin of the vector potential at the nucleus gives sigma = 46 ppm as the basis-set limit. Minimal basis ab initio calculations on C70 predict greatest diamagnetic shielding at the equator and least near the poles of this spheroidal cluster, in good agreement with the experimental assignment of the C-13 NMR spectrum.