The Onuki-Doi Theory of Form Birefringence and Dichroism

In a fluctuating system, both the electric field, E, and the dielectric tensor, e, will undergo random oscillations described by equations (4.42) and (4.43). A solution is sought for this equation so that the mean electric field in the sample is of the form 

Alternatively, equation (4.82) can be averaged and then Fourier transformed to 

The first term, (e), is the intrinsic part of the dielectric tensor, e., and will lead 

If the fluctuations in the dielectric tensor are primarily due to isotropic concentration fluctuations, then using equation (4.49), 

From the above expressions, the form birefringence and dichioism can be calculated. The form dichroism, in particular, has the simple interpretation of being the anisotropy in the second-moment tensor of the structure factor. It is also evident that the form dichroism appears at a higher order in the wave number than the form birefringence. 

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The Onuki-Doi Theory of Form Birefringence and Dichroism 75 which, when compared with (4.83), gives the result that... 

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