Molecular orientational dynamics inK3C60probed by two-dimensional nuclear magnetic resonance

We characterize the orientational dynamics of ${\mathrm{C}}_{60}^{3\mathrm{-}}$ anions in ${\mathrm{K}}_3$ ${\mathrm{C}}_{60}$, using two-dimensional NMR exchange spectroscopy. We find an activated temperature dependence for the reorientation rate between 195 and 220 K, with ${\mathit{E}}_{\mathit{a}}$=460±60 meV. Molecular reorientation proceeds via small (<44°) rotational jumps, implying that ${\mathrm{K}}_3$ ${\mathrm{C}}_{60}$ is more highly orientationally disordered than previously proposed.