Dynamic light scattering from static and dynamic fluctuations in inhomogeneous media

General equations for photon-correlation functions measured by dynamic-light-scattering on inhomogeneous, non-ergodic systems are presented. In contrast to previous studies on the same subject, our derivation includes the most general case that is free from any assumption on the nature of dynamic fluctuations. The present treatment provides a guideline for applying a dynamic-light-scattering technique to investigate dynamic properties of disordered systems in their most general situation where not only static but also dynamic properties depend on position. The well known Siegert relation and Pusey-van Megen equation are shown to be derivable as a special case in our general treatment. Application of the derived equations to real polymeric gel systems is discussed. As further developments, our formulation will be of use in studies of phase transitions and critical phenomena in complex systems.