Abstract

In dynamic light scattering the intensity correlation function is calculated by means of a correlator from the measured scattered fluctuating intensity. Subsequently the intermediate scattering function, or its Fourier transform the dynamic structure factor, can be extracted from the correlation function. This by now classical method has, as any experimental technique, its own limitations. One of the limitations becomes apparent when the intensity correlation function possesses an algebraic tail. It is observed for example in colloidal or polymeric systems undergoing a glass transition^1-3. Then it is possible, but difficult to extract the true intermediate scattering function of the system, even though the system is considered in equilibrium. Non-stationary systems or systems behaving chaotically in time pose a real problem. For a non-stationary system the zero frequency divergence in the power spectrum of the fluctuating intensity precludes any quantitative analysis by means of correlation functions, since an infinite time range should be covered. Examples are the formation of a glass or a gel, and turbulence.

© 1996 Optical Society of America