Far-infrared investigation of C-60 high-pressure-high-temperature polymersand dimer

We report high-resolution far-infrared transmission measurements on 2D rhom bohedral and 1D orthorhombic high-pressure-high-temperature C-60 polymers a nd the doubly-bonded dimer, between 20 and 650 cm(-1). Symmetry-breaking of the linked C-60 balls is evident in splittings and activations of intramol ecular modes. We find overall good agreement with predictions of group theo ry for the reduced-symmetry point groups of the R-polymer and Dimer. An ove rabundance of activated modes between 500 and 600 cm(-1) in the O-polymer m akes a confirmation of its symmetry more tentative. In all three structures , a strong multiplet near 610 cm(-1) suggests a very large splitting or fre quency shift of an I-h C-60 fundamental mode, implying that a weak perturba tion model cannot adequately describe the vibrational properties of bonded fullerenes.