Dynamic probe of dust wakefield interactions using constrained collisions.

The magnitude and the structure of the ion-wakefield potential below a negatively charged dust particle levitated in the plasma-sheath region have been determined. Attractive and repulsive components of the interaction force were extracted from a trajectory analysis of low-energy dust collisions in a well-defined electrostatic potential, which constrained the dynamics of the collisions to be one dimensional. The peak attraction was on the order of 100 fN. The structure of the ion-wakefield-induced attractive potential was significantly different from a screened-Coulomb repulsive potential.