Spectroscopic characterization of pressure modified C-60

Optical data on pressure-temperature treated C-60 are reported. The material associated with the mixture of rhombohedral and tetragonal phases was synthesized under pressure of 3 GPa when treatment temperature was only a little lower than the high-temperature limit of C-60 stability. The substance exhibits very rich infrared and Raman spectra as well as luminescence spectra of an unusual shape. They show that vibrational transitions in the prepared carbon architecture substantially deviate from icosahedral symmetry of buckyballs and exhibit a similarity with lattice phonons in graphite. It may originate from mixing of C-60 modes and vibrations of a layer structure on deformed and weakly bound fullerene molecules. The luminescence spectra reveal three distinct electronic states located below 1.80 eV. One of them responsible for the emission peak at 1.74 eV is very characteristic for the pressure modified fullerene. The data should be useful for the accurate determination of structural changes in C-60 induced by pressure.