Résumé
In this paper, the important role of neutron spectroscopy for the study of the dynamics of C-60 molecules hosted inside single-walled carbon nanotubes (SWNT) is described. We find that the intramolecular vibrations of the fullerene are very sensitive to temperature and that an excess of low frequency modes is observed in the density of states below T=50K. These are strong indications of some coupling between vibrational modes and whole molecule mobility of the confined fullerene. However, no libration modes of the C-60 inside the nanotubes are observed, down to a temperature of 2K, indicating that the order-disorder transition, if it exists, does not show up in the same way that it does for cubic C-60. The lack of such ordering of the C-60 chains inside the nanotubes could be explained by the low dimensionality of this system added to a smooth nanotubes field potential.