Experimental studies on vertical oscillations of few particle vertical structures are described. One and two particle strings were subjected to two types of vertically driven oscillations. The first was electrode driven, which excites the structure as a whole, while the second was laser driven, which excites one particle in the structure only. The latter experiments are highly original, enabling us to excite two vertical resonances in our two particle structures. From the close agreement between our experimental data and theoretical model, several important physical parameters have been estimated, including the charge ratio and the Debye length.

Abstract-Under suitable conditions, micron-sized dust particles introduced into inductively coupled argon plasma form a stable microscopic crystal lattice, known as a Coulomb (or plasma) crystal. In the experiment described, an external axial magnetic field was applied to various configurations of Coulomb crystal, including small crystal lattices consisting of one to several particles, and large crystal lattices with many hundreds of particles. The crystals were observed to rotate collectively under the influence of the magnetic field. This paper describes the experimental procedures and the preliminary results of this investigation.

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