Brownian motion of macromolecules in solution. Inelastic dynamic light scattering

Brownian motion of macromolecules in solution. Inelastic (dynamic) light scattering 

More rigorous consideration of light scattering phenomenon by colloidal or polymer solutions should account for the time effects due to the Brownian motion of their structural elements. 

In Rayleigh-Debye s approximation (subsection 2.1.2), the density correlation function (the dynamic form factor) S q,t) = (p(q,t) p (q,0)) (cf. Kquations 2.3 38,-39) acts as form factor (Debye s function) (Equation 2.1-64). 

The first mode can be regarded as a pulsation when a coil alternately stretches and shrinks (de Gennes, 1968). 

To calculate S(q,t) of a macromolecule, the microscopic density of segments at the point r at the instant t is introduced (Gotlib et al., 1986) 

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