ESR study of high-pressure phases of C-60 fullerene

Face-centered cubic and rhombohedral phases of pressure-temperature treated Csa were investigated bg ESR spectroscopy in the 5 to 550 K temperature range. It was found that the ESR spectra of the former differ only slightly from those of the starting C-60 powder. The intensity of the ESR signal from this phase reduces upon heating the specimens above 480 K. In contrast, the rhombohedral phase shows an intense narrow ESR line which obeys the Curie law and does not change much upon heating. The origin of paramagnetic centers in the high-pressure phases of C-60 and their relationship to the structure of the substances are discussed.