Polarized IR studies of C60F18 single crystals

Optical investigations of C60F18 single crystals using polarized IR radiation have been carried out. The spectral dependence versus polarization angle was established and, together with small linewidths (similar to 5-7 cm(-1)), indicated that the crystal was one-domained with a slight disorder in arrangement of electrical dipole moments. For the first time almost total alignment of molecular dipole moments was established for 300 K. Calculations of the IR spectra for an isolated C60F18 molecule and comparison with the experimental curves have allowed to determine molecules' orientation with respect to the crystal edge. Besides, the temperature dependence of the IR spectra was obtained. The experimentally observed feature in the dependence of linewidth versus temperature at 150-200 K may be connected both with a full ordering of molecules, and alternatively, with an influence of crystal lattice vibrations. (c) 2006 Elsevier B.V. All rights reserved.