A note on the binary interaction potential in complex (dusty) plasmas

The effect of ion-neutral collisions on the potential of interaction between a pair of negatively charged grains in isotropic weakly collisional plasmas is investigated. Two interaction mechanisms are considered: Electric repulsion between like-charged grains and attraction due to the so-called "ion shadow" effect. It is demonstrated that in the presence of collisions, both interaction potentials exhibit Coulomb-like alpha r(-1) decay at large distances. A necessary condition for the existence of long-range attraction is derived. The obtained results are then used to reconsider the possibility of liquid-vapor critical point occurrence in complex plasmas. (C) 2008 American Institute of Physics.