Dynamic Structure Factor of a Diffusing Particle

2 Dynamic Structure Factor of a Diffusing Particle More often than not, the particles move according to the diffusion equation. The transition probability is given by Eq. 3.30. Then 

I gfr) I is an exponentially decaying function with a decay constant of Dk. It is customary to first introduce the decay rate F of gi(r) by 

When the suspension is not spherical or, in general, is a particle with an internal structure such as a linear polymer chain, the decay rate deviates from the one given by Eq. 3.43 at higher scattering angles. The diffusion coefficient defined in the low k limit refers to the overall displacement of the molecule, i.e., the motion for the center of mass. 

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