Dynamic and electronic properties of $\mathrm{Ce}@{\mathrm{C}}_{80}:$ Comparative studies by the time-differential perturbed angular correlation technique with ${}^{140}\mathrm{Ce}$ $\left({\leftarrow }^{140}\mathrm{L}\mathrm{a}\right)$ probes in graphite and diamond

Dynamic and electronic properties of ${\mathrm{Ce}\mathrm{@}\mathrm{C}}_{80}$ as a ${\beta }^{-}$ decay product of ${}^{140}{\mathrm{La}\mathrm{@}\mathrm{C}}_{80}$ were investigated by means of time-differential perturbed angular correlation measurements with ${}^{140}\mathrm{Ce}$ as the probe. Thermal motion of solid state ${\mathrm{Ce}\mathrm{@}\mathrm{C}}_{80}$ with the activation energy of $3.7\pm 2.3{\mathrm{kJ}\mathrm{}\mathrm{mol}}^{\mathrm{-}1}$ was observed at high temperature. Below the freezing temperature of the molecular motion at around 142 K, intramolecular motion of the encaged Ce atom was still observed. Dynamics of endohedral Ce fullerenes are discussed in comparison with previously reported data on ${\mathrm{Ce}\mathrm{@}\mathrm{C}}_{82}$ and ${\mathrm{CeLa}\mathrm{@}\mathrm{C}}_{80}.$ Regarding electronic property of the encaged Ce, comparative studies with the same probes implanted in graphite and diamonds evidently suggest that encaged Ce atoms in fullerene cages possess a $4f$ electron taking the state of ${\mathrm{Ce}}^{3+}$ after ${\beta }^{-}$ particle emission from the excited ${}^{140}\mathrm{La}$ nuclei.