Novel Dynamic Behavior ofCeC82at Low Temperature

Dynamic motion of $\mathrm{Ce}{\mathrm{C}}_{82}$ in the forms of powder and $o$-dichlorobenzene solution is discussed based on time-differential perturbed angular correlation measurements. The observed angular correlations show the presence of two different chemical species of $\mathrm{Ce}{\mathrm{C}}_{82}$. The temperature dependence of the reorientational correlation time abruptly changes at specific temperatures, implying the freezing of the molecular rotation. The data at low temperatures reveal that Ce stays at a certain site for one of the species, whereas for the other the atom has an intramolecular dynamic motion.