Laser-excited waves in a plasma crystal

The radiation pressure of a chopped laser beam is used to excite low-freque ncy (f = 0.4-5 Hz) waves in plasma crystals. The first system studied is a linear chain of spherical plastic particles of 9.47 mu m diameter. The seco nd system is a single-layer crystal with hexagonal structure made of the sa me kind of particles. The measured dispersion and damping of longitudinal c ompressional waves is compared with a model for dust lattice waves in a sys tem of particles interacting by Yukawa-type potentials. From the best fit t he shielding factor is determined. The finding that the measured shielding length is comparable with the interparticle distance is supported by Monte Carlo simulations.