Experimental solution of the local-field problem in discotic liquid crystals

Polarized light-absorption spectra are obtained for single-domain planar-or iented samples of the discotic D-ho. Previously predicted spectral effects induced by resonant dipole-dipole interactions of the molecules are observe d. New methods for determining the parameters of the local field in the D-h o phase are developed which take into account the mixing of the molecular e xcitations. It is shown that the two-dimensional crystalline ordering of th e molecular columns decreases the anisotropy of the local field for this ph ase. (C) 1999 American Institute of Physics. [S0021-3640(99)00613-1].