8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Wed 711:10-14:00P5.5Long-time dynamics of confined colloidal suspensionsJose Luis Arauz-Lara, 1 Beatriz Bonilla-Capilla, 1 and Angeles Ramirez-Saito 11 Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, Zona Centro 78000,San Luis Potosi, MexicoThe long-time collective dynamics of quasi-two-dimensional colloidal suspensions is measured byoptical microscopy. The system consists of charged polystyrene spheres suspended in water andconfined between two parallel plates. Time-dependent pair correlation functions, such as the twodimensionalvan Hove functions and the corresponding dynamic structure factors, are measured fora range of particle concentrations. The van Hove function, which is the radial correlation functionat time t = 0, is observed to evolve in time decreasing its initial structure and becoming flat at longtimes, i. e. , at times when the interparticle correlation is lost. In these systems, the evolution ofthe self- and distinct-part of the van Hove function can be followed independently. Thus, we candetermine the time scale where both quantities start to overlap, establishing a criterion to separateshort from long time scales.5