The fullerene C(60) can be converted into two different structures by high pressure and temperature. They are metastable and revert to pristine C(60) on reheating to 300 degrees C at ambient pressure. For synthesis temperatures between 300 degrees and 400 degrees C and pressures of 5 gigapascals, a nominal face-centered-cubic structure is produced with a lattice parameter a(o) = 13.6 angstroms. When treated at 500 degrees to 800 degrees C at the same pressure, C(60) transforms into a rhombohedral structure with hexagonal lattice parameters of a(o) = 9.22 angstroms and c(o) = 24.6 angstroms. The intermolecular distance is small enough that a chemical bond can form, in accord with the reduced solubility of the pressure-induced phases. Infrared, Raman, and nuclear magnetic resonance studies show a drastic reduction of icosahedral symmetry, as might occur if the C(60) molecules are linked.

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Inelastic light scattering studies of La2Cu04, both pure and doped with lead, over the energy range 0-1 eV have revealed the presence of high-frequency Aig scattering components, in the spectral region 3500-6000 cm, while also providing the complete line shape for the previously reported spin-pair mode of Big symmetry. Two main bands, broad and overlapping, are observed in this region with maxima near 3500 and 5200 cm '. The various spectral features show diAerent resonance behavior. We suggest that a model based upon coupled spin and charge excitations will be required to describe these spectra.