13C NMR evidence for dynamics of nanotubes in ropes

We report on C-13 nuclear magnetic resonance from 10 up to 350 K on single wall carbon nanotubes. The magic angle spinning NMR spectrum shows one isotropic line at 126 ppm and the static spectrum a powder pattern typical for a curved graphene sheet. The T dependence of the spin-lattice relaxation rate T-1(-1) reveals an unusual phenomenon which could be explained by thermally activated small amplitude motion (SAM) of the nanotubes. If above 170 K, diffusion of twistons might be responsible for the local SAM of the C-13 sites, below this transition temperature frozen in twistons could appear with an orientational order of the nanotubes in the ropes.