Linear Dichroism Spectroscopy: Theory

Abstract

Synonyms Linear dichroism spectroscopy

Definition LD is defined as the difference in absorption of two linearly polarized light beams that are polarized at right angles to one another and to the direction of propagation:

LD = A// – A⊥ (1) This notation is normally reserved for uniaxial samples with // denoting the direction of the unique axis. So, although most LD experiments have (or are assumed to have) effective uniaxial orientation, it is better when deriving equations to use the more general definition

LD = AZ – AY (2) where AZ is the absorbance of Z-polarized light, and similarly AY. {X, Y, Z} form what is known as a laboratory-fixed axis system since they are used to identify macroscopic aspects of the experiment. We shall use {x, y, z} for the molecule-fixed axis system where z is the molecular orientation axis. For any one molecule the two axis systems are... Show more