Rovibrational Motion of CO in SolidC60

Solid ${\mathrm{C}}_{60}$ can be intercalated with CO gas in a 1:1 ratio. The rovibrational motion of CO in these samples is studied as a function of temperature by IR and NMR spectroscopy. The observed spectra indicate a gradual transition from nearly free motion of CO at room temperature to hindered motion at low temperature, with only tunneling between symmetry equivalent orientations remaining. The observations are augmented by theory, and details on the local environment of the CO molecules are extracted.