Nondiffusive Brownian motion of deformable particles: breakdown of the "long-time tail".

We study the nondiffusive Brownian motion of both rigid and deformable mesoscopic particles by cross-correlated dynamic light scattering with microsecond temporal resolution. Whereas rigid particles show the classical long-time tail prediction, the transition to diffusive motion of deformable particles presents a striking behavior not explained by the existing hydrodynamic treatments. This observation can be interpreted in terms of a damped oscillatory deformational motion on time scales of the order of the Brownian time. Finally, we show that the nondiffusive Brownian motion depends on the specific flexibility of the particles.