Effects of bound states in the screening of dust particles in plasmas

We study the effects produced by the presence of bound ionic states in the screening of charged grains in plasmas. The study is based on the nonlinear collisionless plasma model with regard to the absorption of plasma particles by grain. It is shown that the bound states are present only in the region limited by a critical distance r(c), which is determined by the asymptotical behavior of the effective potentials inversely proportional to the squared distance. As a result, in the case of very large grain sizes, of the order of three Debye length, the bound ionic states cannot exist at all. The computations evidence that the contributions of the bound states to the effective potentials are insignificant. In the case of small grain sizes, the effective potentials are shown to be very close to those predicted by the linear Debye-Huckel theory. (C) 2002 Elsevier Science B.V All rights reserved.