On the Theory of Excitons in Liquids. II. A Classical Model of Polarization Waves in a Simple Liquid

Recent studies of the localized excited states of condensed matter have been almost exclusively concerned with the properties of crystalline solids. In this paper we construct an analysis of the exciton states of a particular disordered system, namely a simple liquid. We present a model which is an extension of the model previously used by Fano and which allows the construction of a general theory of polarization waves in which the structure of the liquid appears explicitly. Some particular cases of the general form of the dispersion relation of polarization waves are worked out in detail both in the longitudinal and transverse cases. Finally, the possible mechanisms of damping of the exciton waves are briefly discussed.