Electronic spectra of the crystalline polymers of C60:: Photoluminescence study at high pressure

Specific details of the electronic spectra of perfect crystalline polymers of C-60 were studied by means of the photoluminescence spectra measurements at normal conditions and at high pressure up to 4 GPa. The structure of the photoluminescence spectra, the intensity distribution between the principal bands and the pressure-induced shift of the bands differ considerably among the pristine C-60, linear orthorhombic and planar tetragonal and rhombohedral polymeric phases of C-60. Unlike the planar polymers of C-60, the linear orthorhombic polymer exhibits irreversible changes in the photoluminescence spectrum under simultaneous application of high pressure and laser irradiation. The changes observed in the photoluminescence spectra of the planar polymeric phases of C-60, as compared to the pristine material, are discussed in relation to the corresponding changes in the calculated electronic structure of the pristine C-60 and its polymeric phases. The observed photoluminescence spectral structure along with the pressure behavior of the photoluminescence spectra are very sensitive to the structure of the polymers as well as to the C-60 cage deformations and can be used to effectively characterize the various polymeric phases of C-60.