3-DIMENSIONAL STRUCTURE IN A CRYSTALLIZED DUSTY PLASMA

Direct imaging of the three-dimensional structure of a system of parti cles suspended in a dusty plasma reveals coexisting bcc and simple-hex agonal crystal structures. The coexistence is attributed to a bistabil ity which appears in a recent theory predicting an attractive region i n the plasma down stream of a particle in an ion flow. Bath structures are polycrystalline, and they have short-range translational but quas i-long-range orientational order within a grain. This ordering is char acteristic of the two-dimensional hexatic phase, but the existence of grain boundaries is not.