C-13 NMR IN IODINE AND POTASSIUM INTERCALATED C-60 SOLID

Iodine intercalated C60, I2.29C60, was studied by C-13 NMR above 160 K. A sharp NMR signal and a strong temperature-dependent spin-lattice relaxation time, T1, indicated a presence of C60 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 T1 (40 +/- 5 sec at room temperature). In K3C60, metallic behavior, T1 T approximately 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 I2.29C60 was estimated to be smaller than 0.12 of that in K3C60, assuming a relationship between N(E(F)) and T1T for normal metals.