Direct experimental observation of binary agglomerates in complex   plasmas
  A defocusing imaging technique has been used as a diagnostic to identify binary agglomerates (dimers) in complex plasmas. Quasi-two-dimensional plasma crystal consisting of monodisperse spheres and binary agglomerates has been created where the agglomerated particles levitate just below the spherical particles without forming vertical pairs. Unlike spherical particles, the defocused images of binary agglomerates show distinct, stationary/periodically rotating interference fringe patterns. The results can be of fundamental importance for future experiments on complex plasmas. 
M. Chaudhuri, V. Nosenko, C. Knapek, U. Konopka, A. V. Ivlev, H. M.   Thomas and G. E. Morfill
physics.plasm-ph cond-mat.soft