Light, circularly-polarized

Circular dichroism (CD) is a spectroscopic method which depends on the fact that certain molecules interact differently with right and left circularly polarized light. Circularly polarized light is chiral, that is, occurs in two nonsuperimposable forms which are mirror images of one another, and is described further below. To discriminate between the two chiral forms of light, a molecule must be chiral, which includes the vast majority of biological molecules. 

A common feature of enantiomeric forms of the drug is rotation of plane of polarized light with the same angle to the left or to the right. This rotation comes from absorption of one of the two components of linear polarization of light (circular polarization dextro- or levorotatory). 

An interesting aspect of two-photon spectroscopy is that some polarization infonnation is obtainable even for randomly oriented molecules in solution by studymg the effect of the relative polarization of die two photons. This is readily done by comparing linearly and circularly polarized light. Transitions to A states will absorb linearly polarized light more strongly than circularly polarized light. The reverse is true of transitions to B ... 

Figure B1.3.A.9. Diagram depicting the angles used in scattermg experiments employing linearly and circularly polarized light. The subscripts i and s refer to the incident and scattered beam respectively.

For a circularly polarized light experiment, one can measure the cross sections for either right (r) or left (1) polarized scattered light. Suppose that right polarized light is made incident on a Raman active sample. The general expressions for the Raman cross sections are [176]... 

C2.15.2 a right circularly polarized wave is illustrated. As tire wave propagates, Eq sweeps out a circle in tire x-y plane. It is clear tliat, given a well characterized light source, tliere are many attributes we can attempt to control (wavelengtli, polarization, etc.) tire question is how to generate well-characterized light ... 

Figure C2.15.2. Right circularly polarized light. As tire wave propagates tire resultant E sweeps out a circle in tire x-y plane.

The macroscopic optical analysis of these effects requires the introduction of two complex indexes of refraction for the ferromagnetic material, one for lefr-circu-larly polarized light and another for right-circularly polarized light, which to first order, are given by... 

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