Dynamics of CO molecules in solid C60 as a function of cavity size

The rovibrational motion of CO intercalated in the octahedral site of solid C-60 is monitored as a function of pressure via infrared (IR) absorption spectroscopy. The increased hindering of the motion of the CO molecule, when the pressure is tuned from ambient to 32 kbar, is reflected in a dramatic change in the observed IR spectra. A large part of the transition from translationally and rotationally free molecules in a box to rigidly oriented molecules can thus be studied experimentally, and accurately described theoretically.