Electronic circular and linear dichroism

Circular dichroism (CD) is the difference in absorption of light left and right circularly polarized, and linear dichroism (LD) is the difference in absorption of light linearly polarized parallel and perpendicular to an orientation axis. These polarized light spectroscopy techniques can be used to determine structural information about polymeric systems. CD spectra give information about the asymmetric character of the molecules in a solution, whereas LD gives data on relative orientations of subunits of oriented polymeric system. This article outlines what the techniques are, from where the signals originate and illustrates spectra that can be obtained and how they can be analyzed.