Recent NMR experiments by Singer et al. [Singer et al. Phys. Rev. Lett. 95, 236403 (2005).] showed a deviation from Fermi-liquid behavior in carbon nanotubes with an energy gap evident at low temperatures. Here, a comprehensive theory for the magnetic field and temperature dependent NMR 13 C spin-lattice relaxation is given in the framework of the Tomonaga-Luttinger liquid. The low temperature properties are governed by a gapped relaxation due to a spin gap (∼ 30 K), which crosses over smoothly to the Luttinger liquid behaviour with increasing temperature.PACS numbers: 71.10. Pm,71.20.Tx, Low dimensional carbonaceous systems, fullerenes, carbon nanotubes (CNTs), and graphene display a rich variety of exotic states and strongly correlated phenomena. These include superconductivity in alkali doped fullerenes 1 , quantized transport in singlewall carbon nanotubes (SWCNTs), and massless Dirac quasi-particles showing a halve integer quantum Halleffect in graphene even at room temperature. A compelling correlated state of one-dimensional systems is the Tomonaga-Luttinger liquid (TLL) state. The TLL state has been suggested to describe the low energy properties of CNTs with a single shell, the single-wall carbon nanotubes 2,3,4,5,6 . Transport 7 and photoemission studies 8,9 provided evidence for the existence of the TLL state in SWCNTs. In these studies, power-law behavior of temperature and bias dependent conductivity and a power-law Fermi edge was observed, respectively.Nuclear magnetic resonance (NMR) is a powerful method to characterize correlated states of materials as it is sensitive to the density of states near the Fermi edge. For a material with a Fermi-liquid state, the temperature dependent spin-lattice relaxation time, T 1 follows the so-called Korringa temperature dependence for which 1/T 1 T is constant. Recently, 13 C enriched SWCNTs were grown inside carbon nanotubes from 13 C enriched fullerenes 10 . This allowed a high precision measurement of T 1 in small diameter SWCNTs by Singer et al. 11 . A tentative fit of the experiments with a gapped Fermi liquid type density of states (DOS) indicated overall agreement but obvious discrepancies in detail. When the magnetic field and temperature dependent data for T 1 were fitted with this phenomenological model a gap at the Fermi surface with 2∆ ≃ 40 K opened already above room temperature, i.e. its T c is larger than 300 K. This strongly violates the 2∆/k B T > 3.52 relation, thus simple mean field theories are not applicable 12 . Also, the phenomenological description can not account for the strong overshoot of 1/T 1 T when T approaches the gap.Here, we analyze the NMR results in the framework of the Luttinger liquid and Luther-Emery liquid pictures (interacting one-dimensional electrons without and with a gap, respectively). At high temperatures, the former dominates, while the latter accounts for the dominance of a spin gap at low temperatures. We show that the temperature and magnetic field dependent T 1 of 13 C can be explained in the TLL scenario wit...