Reorientational dynamics of C60 in the solid state. An avoided level-crossing muon spin resonance study Original Research Article

The dynamics of the muonium (Mu) adduct to C60 in the crystalline state have been investigated using avoided level crossing muon spin resonance (ALC-μSR). The motion of C60 in the orientationally ordered phase (T < 260 K) is well described by a spherical diffusion or isotropic jump-reorientation motion with an Arrhenius activation energy of 176(1) meV and a frequency factor of 2.95(13) × 10−12 s. This is in striking contrast to the behaviour of MuC70 adducts whose reorientational motion fits well in a pseudo-static model with a temperature dependent order parameter.