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Title: Mixing of molecular excitation in a uniaxial liquid crystal

The influence of the mixing of molecular excitations due to local-field effects on the dielectric and spectral properties of uniaxial liquid crystals is investigated. The general properties of the spectrum of transverse optical excitations of the medium, viz, the sum rules for the oscillator strengths, frequencies, and damping constants of the dielectric function resonances, are established. The restricted applicability of the idea of a back ground polarizability (dielectric function) in the analysis of the mixing of molecular excitations is demonstrated. Mixing is taken into account in deriving new dispersion formulas for the imaginary and real parts of the dielectric tensor, which differ significantly from those used in the literature. A range of applicability has been established for the latter. Qualitative and quantitative interpretations of controversial experimental data for an extensive list of objects are given. The occurrence of mixing of dipole-active molecular vibrations, whose intensity has been found to be strongest for polyphilic objects that form nonchiral ferroelectric phases, has been demonstrated for molecular liquids and uniaxial liquid crystals from various chemical classes for the first time. The mixing of molecular excitations is considered as a possible mechanism for {open_quotes}polarization catastrophe{close_quotes} in liquid crystals having a soft mode in hthespectrummore » of transverse optical modes of vibration for the high-temperature phase. 53 refs., 1 fig.« less
Authors:
 [1]
  1. L.V. Kirenskii Inst. of Physics, Krasnoyarsk (Russian Federation)
Publication Date:
OSTI Identifier:
121681
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Experimental and Theoretical Physics; Journal Volume: 81; Journal Issue: 1; Other Information: PBD: Jul 1995
Country of Publication:
United States
Language:
English
Subject:
66 PHYSICS; LIQUID CRYSTALS; MIXING; DIELECTRIC PROPERTIES; EXCITATION; OSCILLATOR STRENGTHS; RADIATION EFFECTS; THERMODYNAMICS; OPTICAL PROPERTIES