MOLECULAR-DYNAMICS OF MU+-C60 RADICAL IN SOLID C60

The molecular dynamics and electronic structure of the mu+-C60 radical in crystalline C60 have been studied using muon spin rotation and relaxation. At room temperature mu+-C60 appears to be in a state of quasifree rotation. At the critical temperature T(S) = 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.