Dynamics and orientational order of a charged granular fluid

The dynamics and orientational order of a charged quasi-2D granular system at low packing fractions are examined experimentally. We find significant orientational order that does not vary monotonically. We also find a correlation between the orientational order parameter \6\ and the system's dynamics as characterized by typical relaxation times obtained from the self-intermediate scattering function and from the mean squared displacement. These effects are explained in terms of the interplay between electrostatic repulsions and separations between shells of neighbors, and the role of collisions.