Longitudinal field repolarization studies of reorientational dynamics in the fullerenes C₆₀ and C₇₀

LFμSR studies on the pure fullerenes C₆₀ and C₇₀ show temperature dependent features associated with the reorientational behaviour of the fullerenyl radicals MuC₆₀ and MuC₇₀ in the crystalline host substrate. If not excluded from the experimental setup, molecular oxygen undergoes spin exchange reactions with the radicals. The data for C₆₀ correspond to a situation effectively static at 150 K and fully averaged to isotropy at 300 K, while for C₇₀ the data conspicuously do not conform to the predictions of the pseudostatic model employed in ALC-μSR studies.