APPARENT CIRCULAR DICHROISM OF ORIENTED SYSTEMS

Measurements of circular dichroism (CD) are usually carried out by the method of Grosjean and Legrand. The CD spectrum of an oriented system obtained by this method can differ considerably from the true spectrum because of the effects of linear dichroism (LD) and birefringence. This paper examines the relationship between true and apparent CD spectra for an anisotropic uniaxial specimen having its optic axis perpendicular to the direction of the light beam. Among the features of the apparent CD spectrum are underestimation of CD, red and blue shifts, and small spurious bands. The method may readily be adapted to the measurement of the LD of an optically active oriented system, and the apparent LD spectrum should differ in only a minor way from the true spectrum. Several examples of apparent CD spectra are provided by calculations which proceed from assumed forms of the true CD and LD spectra. © 1969, American Chemical Society. All rights reserved.