NEW METHODS FOR STUDYING THE ORIENTATION ORDER OF UNIAXIAL MOLECULAR FILMS ON THE BASE OF OPTICAL DATA

Aver'yanov, E. M. LIQUID CRYSTALS AND THEIR APPLICATION DOI: 10.18083/LCAppl.2020.1.41

The components epsilon((l,2)j )(omega) of the dielectric function epsilon(j) (omega) = epsilon(lj) (omega) + i epsilon(2j) (omega) for uniaxial molecular film in the region of an isolated absorption band of the light polarized along (j = parallel to) and across (j = perpendicular to) the film optical axis were considered. The connection of the components with the orientation order parameter S of the dipole moments of molecular transitions corresponding to a given absorption band was established. New methods for determining S are developed. They are confirmed for the organic semiconductor PTCDA film of nanoscale thickness with the known dependences epsilon((l,2)j )(omega) in the transparency and low frequencyelectron absorption regions. The effect of the orientation order and anisotropy of dynamic dipole-dipole intermolecular interactions (local-field effects) on the maxima position of the epsilon(2j)(omega) bands was shown.