Laser-generated waves and wakes in rotating ion crystals

Locally excited plasma waves are generated in a Coulomb crystal by pushing with radiation pressure on a rotating cloud of laser-cooled Be-9(+) ions. The waves form a stationary wake that is directly imaged through the dependence of the ion fluorescence on Doppler shifts, and theoretical calculations in a slab geometry are shown to accurately reproduce these images. The technique demonstrates a new method of exciting and studying waves in cold ion clouds.