STATIC AND DYNAMIC LIGHT-SCATTERING OF COLLOIDAL GASES, LIQUIDS AND CRYSTALS

Static and dynamic light-scattering measurements are made for colloida l-crystals, -liquids and -gases of silica spheres, 103 nm in diameter, in the exhaustively deionized suspension and in the presence of sodiu m chloride. Sharp peaks in the scattering curve are observed, for the first time, for the colloidal crystals in very diluted aqueous suspens ion. The product of the effective diffusion coefficient and the scatte red light intensity is found constant over the whole range of the scat tering angle measured for the colloidal crystals and liquids. Three an d two dynamic processes have been extracted separately from time profi les of autocorrelation function of colloidal crystals and liquids, res pectively from Marquadt histogram analysis. Decay curves of colloidal gases are characterized by a single translational diffusion coefficien t, D-0. D-0 of the gases is always lower than the calculation from the Stokes-Einstein equation with the true diameter of spheres, and incre ases as ionic concentration increases. These experimental results emph asize the important role of the expanded electrical double layers on t he diffusive properties in the colloidal crystals, liquids and gases.