Scattered intensity in the zero angle limit

At q = 0, the expressions of the cross-section per unit volume (7.2.5) and of the scattered intensity (7.2,54) are divergent. It is proper to consider here the finite quantities 

Taking (7.3.8) into account and considering that the monomer concentration is Crf = V, we can also write 

in the zero angle limit, the scattered intensity is related to the mean square fluctuations of the number of molecules (and also of the number of monomers) in the irradiated volume. 

1 Scattering by a homogeneous solute in the zero-angle limit The solute is homogeneous if all the monomers are the same. 

The fluctuation of the number of links per chain is determined separately. In fact, we showed that [see (7.3.1) and (7.3.2)] 

---