Theoretical Approach to the Measurement of the Induced Linear Dichroism of Rigid Macromolecules

A comprehensive theory is developed in terms of the principal molar extinction coefficients (epsilon(ii)) of rigid, isolated, rodlike macromolecules when subjected to orienting force fields. The theory embraces the conventional transverse parallel and perpendicular arrangements and the novel longitudinal dichroism method where the light beam and applied field traverse the system concomitantly. Both transverse and longitudinal measurements are considered when the initial light beam. is unpolarized. It is shown that unpolarized light yields as much molecular information as the polarized methods used hitherto. Equations also are given in terms of a single repeating chromophore (epsilon(0)) as if at a specific direction (alpha) to the molecular backbone.