Molecular dynamics of μ+-C60 radical in solid C60

The molecular dynamics and electronic structure of the mu(+)-C60 radical in crystalline C60 are studied using muon spin rotation and relaxation. At room temperature mu(+)-C60 appears to be in a state of quasi-free rotation. At the critical temperature TS = 260 K the local electronic structure and molecular dynamics change discontinuously as expected for a first-order phase transition. The correlation times for reorientation are remarkably close to those determined by recent NMR experiments on C60, suggesting that the molecular dynamics of mu(+)-C60 are strongly coupled to those of its C60 neighbors. (Author)