Structure of marginal and fully developed colloidal liquids

The structures of three colloidal liquids at their triple points are studie d. The interparticle attraction in these liquids, induced by the depletion effect of free polymer, has variable range. In one case, the liquid state i s "marginal"-in the phase diagram the critical point lies nearly on the lin e of triple coexistence. Structure factors of the liquids, measured by anew application of two-color dynamic light scattering, show that their local s tructures are similar, while long-range fluctuations increase as the liquid s become more marginal. [S0031-9007(98)08136-8].