Experimental observation of single-file diffusion of Brownian particles

The self-diffusion of particles restricted to one-dimensional channels is termed single-filc difTusion if individual particles are unable to pass each otlicr. We cmploy thc interference pattern of two coherent lascr hcaii~s lo confinc clcclricall y charged polystyrene colloids in parallel "optical channels" formed by light forces arid study the particle Q -H. Wci . C. Rcchinycr (X) . P. 1,cidcrcr diffusion within these channels by Faculty of Phys~cs University of Konslauz optical. microscopy. For small chanPostfach M676. D-78457 Konstanz nel spacings the particles can elecCitirnanb trically couplc bclwccn adjacent channels and their mcan squarc displacement along these channels at long ohscrvatioi~ timcs r is proportional to t . For large channel spacings, however, where the coupling of particles is largely reduced, we find thc rncan square displacement to be proportional to P ?.which signifies the occurrence of single-file