LOCALIZED DYNAMIC LIGHT-SCATTERING - PROBING SINGLE-PARTICLE DYNAMICSAT THE NANOSCALE

We developed an experimental technique which probes the dynamics of a single colloidal particle over many decades in time, with spatial reso lution of a few nanometers. By scattering a focused laser beam from a particle observed in an optical microscope, we measure its fluctuation s via the temporal autocorrelation function of the scattered intensity g(t). This technique is demonstrated by applying it to a single Brown ian particle in an optical trap of force constant k. The decay times o f g(t), which are related to the particle position autocorrelation fun ction, scale as k(-1), as expected from theory.