Orientational Dynamics of the ${\mathrm{Sc}}_3$ Trimer in ${\mathrm{C}}_{82}$: An EPR Study

Electron paramagnetic resonance experiments on endohedral ${\mathrm{Sc}}_3$ in ${\mathrm{C}}_{82}$ show 22 hyperfine coupling split transitions with unusually large linewidths. Both the nuclear hyperfine coupling and the linewidths are found to be strongly temperature dependent. The data show that the three Sc ions are equivalent, and strongly suggest that they form a trimer which rapidly reorients within the ${\mathrm{C}}_{82}$ cage. A simple model is proposed which is in good agreement with the data.