Shaded regions are forbidden by sphere-wall contact, given the fit estimates for the wall locations. We determined the absolute positions of the glass walls by observing the influence of a steady Poiseuille flow on the particle's motion. Typical examples at the midplane of the slit pore appear in Fig. The peaks' drifts, plotted in Fig. Fitting to Eq.
Errors primarily reflect the experimental uncertainty of in the increment between tweezer locations.
Without loss of generality, we set and measure starting heights from the lower glass surface. The evolution of the distributions' widths over time, shown in Fig. Results are summarized in Fig. 3 . The sphere's diffusivity is strongly suppressed near either wall, and falls well below even along the midplane. Height dependence of the in-plane diffusion coefficient for a Brownian sphere in a slit pore.