Spectral features of polarized light absorption and anisotropy of a local field in the D-ho discotic

The polarized IR absorption spectra of monodomain planar-oriented films of a discotic liquid crystal D-ho are obtained for the first time. The spectra l effects induced by the resonance dipole-dipole interaction of molecules, which have been predicted earlier, were observed. It was found that molecul ar excitations in isotropic and liquid-crystal phases are mixed due to loca l-filed effects and this mixing affects the relative intensity and dichrois m of the absorption bands. New methods were suggested for measuring the loc al-field parameters in the D-ho phase from intensities and positions of the polarized absorption bands taking into account the mixing of molecular exc itations. The two-dimensional crystal lattice of molecular columns was show n to reduce the local-field anisotropy of this phase. (C) 2000 MAIK "Nauka/ Interperiodica".