FREE AND LOCALIZED EXCITONS IN THE LUMINESCENCE SPECTRUM OF C-60 CRYSTALS AT HIGH-PRESSURE

The luminescence spectra of C-60 Single crystals are studied at T cong ruent to 10 K and pressure up to 4.0 GPa. It is observed that as the p ressure increases, one fine-structure band in the spectrum intensifies sharply and dominates at pressures P greater than or equal to 1.7 GPa . The pressure shift of this band is much larger than the shift of oth er bands in the spectrum, and its magnitude correlates with the pressu re dependence of the band gap. It is shown that this band could be due to radiative recombination of free Frenkel excitons. (C) 1998 Amenica n Institute of Physics.