Raman spectroscopy and x-ray diffraction measurements onC60compressed in a diamond anvil cell

Abstract

Using Raman spectroscopy, we present evidence for pressure-induced phase transitions of ${\mathrm{C}}_{60}$ compressed up to 31.1 GPa in a diamond anvil cell at room temperature. No significant change is observed in the Raman spectra upon release of pressure from 31.1 GPa down to almost ambient; the material retains its high pressure phase present at 31.1 GPa. By using x-ray diffraction measurements with a 300-\ensuremath{\mu}m-diameter collimated x-ray beam, we identify the high-pressure (31.1 GPa) structure of the material. It is found to be a mixture of the body-centered orthorhombic (Immm), rhombohedral $(R3\ifmmode\bar\else\textasciimacron\fi{}m),$ and an unidentified phase.