Scattering by an assembly of identical anisotropic polarizable elements

2 Scattering by an assembly of identical anisotropic polarizable elements 

When the polarizable elements are anisotropic, in each site j, the polarizable element has its own orientation. 

In the expression giving the cross-section associated with an initial state I 

Let us calculate (fco, 0), the average of Xi v(ko 0) over orientations. The diagonal (/ = /) and non-diagonal (/ /) terms will be treated separately 

The calculation of the first term is given by eqn (6.3.78). Let us examine the term y, / /. We admit that the averaging over the orientations concerns only the factor Tr Tt o T rv and we shall show that the average is independent of the indices j and / then we shall be able to factorize the exponential as in the isotropic case. 

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