An infrared study on CO intercalated in solid C60

The infrared (IR) absorbance spectra of CO intercalated in solid C-60 have been measured as a function of temperature. The spectra show a gradual transition from a nearly free rotation of the CO molecules to a situation where their rotational motion is severely hindered. The hindering of the rotational motion of CO caused by the surrounding C-60 molecules is found to be comparable to that observed for CO dissolved in a liquid. Good agreement is found between quantum mechanically calculated spectra and the measured IR spectra. The intermolecular van der Waals vibrations of a CO molecule rattling in the octahedral site of the C-60 lattice have been observed at low temperatures. The IR spectra of CO intercalated in C-70 are measured and compared to those observed for CO intercalated in C-60. (C) 1999 American Institute of Physics. [S0021-9606(99)00904-6].