ROTATIONAL-DYNAMICS OF SOLID C-70 MONITORED BY POSITIVE MUON SPIN LABELS

We report the results of an avoided-level-crossing muon spin resonance study of a muonated radical Of C70 between 73 and 310 K. The temperat ure-dependent averaging of the anisotropic hyperfine interaction of th e polarized muon spin label is interpreted in terms of the reorientati onal dynamics of the fullerene. Uniaxial rotation about the long molec ular axis appears likely even at 73 K. Reorientational disorder then s ets in gradually at 160 K with a small anisotropy persisting across th e phase transition in the vicinity of 270 K into the plastic phase.