Light scattering in one-component liquids

Light scattering in one-component liquids (including the region of critical opalescence) is of great importance in solving a number of problems discussed in this book. 

Dynamic light scattering in one-component liquid is the beginning of the consideration of this phenomenon as well as of the investigative method. 

The intensity of light scattered from a fluid system increases enormously, and the fluid takes on a cloudy or opalescent appearance as the gas-liquid critical point is approached. In binary solutions the same phenomenon is observed as the critical consolute point is approached. This phenomenon is called critical opalescence.31 It is due to the long-range spatial correlations that exist between molecules in the vicinity of critical points. In this section we explore the underlying physical mechanism for this phenomenon in one-component fluids. The extension to binary or ternary solutions is not presented but some references are given. 

Near the critical temperatures of both lower and upper consolute boundaries, the spatial correlations of densities within the liquid-phase sfructure extend over longer-than-usual distances. Near-critical liquids display, for this reason, unusually intense scattering of visible light ( critical opalescence ), but this phenomenon is in no sense unique to surfactant solutions. Critical opalescence is universally observed near critical points, even in one-component systems such as carbon dioxide, water, and so forth [68]. 

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