NMR chemical shift of single-wall carbon nanotubes

We report calculation of the NMR chemical shift anisotropy (CSA) tensor σ^↔ of single-wall carbon nanotubes, within the London approximation (ring currents contribution). Our results indicate that the isotropic line as measured by high resolution experiments is splitted about 11 ppm between metallic and semiconductor nanotubes. We carefully check that this result remains valid and observable when the bundle packing is taken into account. The resulting broadening is around 20 ppm, but reduces onto a sharp lorentzian (< 1 ppm) when averaging by high resolution NMR measurements.