13C nuclear relaxation in the normal state of the K3C60 superconductor

13C NMR results on K3C60 showing that nuclear relaxation is nonexponential below 250 K. The nonexponential nuclear relaxation at low temperatures is an intrinsic property of the frozen molecular motion state and is associated with intramolecular variations of the electron spin density distribution. Dipolar coupling to the electron spins at the Fermi level of the carbon pπ - t1u band is identified as the dominant source of 13C relaxation. The measured mean value of (T1T)-1 is determined not only by the total density-of-states at the Fermi level but also by the intramolecular electron spin density distribution. (orig.)