Abstract
The dynamics of confined systems is of major concern for both fundamental physics and applications. In this Letter, the dynamics of C-60 fullerene molecules inside single walled carbon nanotubes is studied using inelastic neutron scattering. We identify the C-60 vibrations and highlight their sensitivity to temperature. Moreover, a clear signature of rotational diffusion of the C-60 is evidenced, which persists at lower temperature than in 3D bulk C-60. It is discussed in terms of confinement and of reduced dimensionality of the C-60 chain.