FIGURE 5.

Experimental spatial maps for the polystyrene beads. (a) Two different sizes of polystyrene beads were used in a single experiment: 200 nm and 500 nm. The beads were in separate microcapillary tubes oriented at an angle with respect to the optical axis and mounted on a homemade microscope sample chamber. Yellow box represents field of view of microscope. (b) Spatial map of the decay rates in the field of view. Note the faster diffusion of the 200-nm beads, as expected. (c) Spatial map of the mobile fractions, obtained using TH Eq. 56, in the same field of view. A zero on the scale implies that most of the scattering centers are immobile whereas unity implies all of the scattering centers are mobile. Both sizes of the beads show a large mobile fraction: for the 200-nm beads, β_avg = 0.63 and for the 500-nm beads, β_avg = 0.42. The 200-nm beads show a smaller spread of the degree of mobility than the 500-nm beads.