Theory of depolarized molecular light scattering

The theoretical studies on depolarized molecular light scattering are reviewed. Chapter 2 is devoted to the phenomenological theories, mainly the relaxation theories of M. A. Leontovich and S. M. Rytov. The general symmetry properties of the scattering cross sections are treated. The theory of the depolarized component $I_{VH}(\omega)$ is presented in detail on the basis of the fluctuation-dissipation theorem, with account taken of two internal relaxation parameters. This theory permits one to explain the experimentally observed fine structure of the tail of the Rayleigh line. A generalization of the theory for taking account of the antisymmetric part of the tensor of the dielectric-constant fluctuations is discussed. Chapter 3 is devoted to statistical-mechanical methods. The development is traced of ideas on the molecular mechanisms of scattering and depolarization of light, and methods are treated of determining the scattering cross sections in terms of the characteristics of individual particles or groups of them. The results of Mori's linear reaction theory are briefly presented, and it is used to establish the form of the equations that determine the evolution of the parameters that enter into the scattering cross section. It is shown that the statistical theories give results that agree with the phenomenological theory of S. M. Rytov, and they permit one to give a molecular-kinetic interpretation of the relaxation parameters that figure in it.