Brownian dynamics of a sphere between parallel walls

We describe direct imaging measurements of a colloidal sphere's diffusion b etween two parallel surfaces. The dynamics of this deceptively simple hydro dynamically coupled system have proved difficult to analyze. Comparison wit h approximate formulations of a confined sphere's hydrodynamic mobility rev eals good agreement with both a leading-order superposition approximation a s well as a more general all-images stokeslet analysis.