NMR INVESTIGATION ON MOLECULAR-DYNAMICS OF C-60 AND C-70 SOLIDS

C-13-NMR was employed to study C60 molecular dynamics in pure C60 crys tals prepared by sublimation technique and by evaporation of CS2-solut ion of C60. The C60 molecular dynamics in the CS2-grown crystal with o rthorhombic (OR) structure was significantly changed by heat-treatment s. This behavior was assigned to a structural conversion of OR to FCC (face centered cubic) by heat-treatment and also to annealing effect o f defects in the crystal. C70 molecular dynamics was also studied in P ure C70 crystal. The C70 molecular rotation was found to be more restr icted than those of C60 molecule in the crystals. It was suggested tha t an anisotropic molecular rotation is dominant below approximately 28 0K in the time scale of NMR line width (approximately 20musec).