Optical Properties of Molecular Aggregates. II. Classical Theory of the Refraction, Absorption, and Optical Activity of Solutions and Crystals

Abstract

Classical theory is used to derive the optical parameters (refraction, extinction coefficient, reflectivity, rotation, and ellipticity) of a macroscopic sample containing aggregated monomer chemical units. The samples considered are dilute solutions of molecular aggregates or polymer molecules, and molecular crysstals. In this theory, each electronic transition of a monomer is represented by an electronic and a magnetic oscillator with complex polarizabilities which are evaluated empirically from the absorption and optical activity of unaggregated monomers. The complex refractive index for a refracted wave in the sample is obtained from Maxwell's equations and the electric and magnetic polarizations, taking into account Coulomb interactions between the oscillators. The optical parameters at any frequency are evaluated from the refractive indices for linearly or circularly polarized light. The results agree, in the same order of approximation, with those derived by several quantum theories. Sum rules are derived for the conservation of the monomer oscillator strengths and rotational strengths in the aggregates.