Oscillations of few particle vertical structures

Experiments on the excitation of vertically aligned particle resonances are presented. A two particle string was driven vertically and horizontally by electrostatically and laser driven oscillations through a range of frequencies. The laser excitation technique allows us to drive one particle and observe the response of another, whereas in earlier experiments single particle systems were excited to vertical resonance. From the close agreement between our model and the experimental resonance curves, the charges of the top and bottom particles were established and a value for the Debye screening length and interparticle forces were estimated