Vibrational Modes and Instabilities of a Dust-Particle Pair in a Complex Plasma

Vibrational modes and instabilities of a dust-particle pair in a terrestrial laboratory complex plasma are investigated by employing an analytical method whereby the plasma wakefield induced by an external electric field is modeled using an image-charge method. It is found that for both horizontally and vertically aligned dust-particle pairs in equilibrium, four normal modes exist. Variations of the confinement parameters cause a single type of instability in the horizontal pair and two types of instabilities in the vertical pair.