We report measurements of the optical absorption spectrum of solid ${\mathrm{C}}_{60}$ in the pressure range from 0 to 40 GPa. At low pressure we find a linear shift of the absorption edge of -0.14 eV/GPa eV. Above 20 GPa, the fullerenes transform irreversibly to amorphous carbon; we find no evidence of transparency greater than that of amorphous carbon produced by other means.

• Received 13 October 1992

DOI:https://doi.org/10.1103/PhysRevB.47.4146