Résumé:

Inelastic neutron scattering investigations of the orthorhombic (O), tetragonal (T), and rhomboliedral (R) pressure-polymerized phases of C-60 as well as the pressure-dimerized state give evidence for differences in the responses of low-energy excitations between these phases. These differences are assigned to changes in low-energy interball modes dynamics as a function of the structure of pressure-polyutmerized phases. Far-infrared transmittance measurements complete the information of the low-frequency vibrational dynamics of these phases. The temperature dependence of these low-frequency excitations reveals a strong anharmonicity and possible phase transitions.