Energy distributions of neutrons scattered from solid C-60 by the beryllium detector method

We measured the energy distribution of neutrons scattered from polycrystalline C-60, using a high-resolution filter-analyzer spectrometer. In the energy range 30-90 meV (242-726 cm(-1)) we observed a rich spectrum that we fitted to a sum of 15 Gaussian functions, each of which is assigned to one or a set of several degenerate normal vibrational modes of the C-60 molecule. We also observed two broad features in the energy range from 90-130 meV (726-1049 cm(-1)). Our results are generally in excellent agreement with published spectroscopic data. Detailed comparisons with the results of several first principles calculations suggest that present-day theories can predict the internal vibrational frequencies of C-60 rather well, at least in the 30-90 meV range of energies.