13C-NMR in Iodine and Potassium Intercalated C60Solid

Abstract

Iodine intercalated C 60 , I 2.29 C 60 , was studied by 13 C NMR above 160 K. A sharp NMR signal and a strong temperature-dependent spin-lattice relaxation time, T 1 , indicated a presence of C 60 molecular rotation much higher than 10 kHz at least down to 160 K. No evidence of metallic characteristics was found in the NMR shift (143±1 ppm) and the T 1 (40±5 sec at room temperature). In K 3 C 60 , metallic behavior, T 1 T ∼constant, was observed at the carbon sites between 20 K and 100 K. Electronic density of states at the Fermi level, N ( E F ), in I 2.29 C 60 was estimated to be smaller than 0.12 of that in K 3 C 60 , assuming a relationship between N ( E F ) and T 1 T for normal metals.