Structure of the ion wakefield in dusty plasmas

The magnitude and structure of the ion wakefield potential below a single negatively charged dust particle levitated in the plasma sheath region were measured using a test particle. Attractive and repulsive components of the interaction force were extracted from a trajectory analysis of low-energy collisions between different mass particles in a well-defined electrostatic potential that constrained the dynamics of the collisions to one dimension. As the vertical spacing between the particles increased, the peak attractive force decreased and the width of the potential increased. For the largest vertical separations measured in this study, the lower particle does not form a vertical pair with the upper particle but rather has an equilibrium position offset from the bottom of the parabolic potential confining well.