First experimental investigations of spherical three-dimensional plasma crystals consisting of hundreds or thousands of micrometer-sized polymer particles suspended in a radio-frequency gas discharge are described. These “Coulomb balls” are not subject to the formation of dust-free regions (voids) and have an unusual structure of nested crystalline shells. While small systems are in a solid phase, large systems show melting effects.

• Received 10 May 2004

DOI:https://doi.org/10.1103/PhysRevLett.93.165004