Nonlinear shielding and electron density enhancement in moderately coupled plasmas

As the plasma coupling grows, the electron density in the vicinity of the central ion increases appreciably, and the atomic reaction rates evaluated with the free Maxwell distribution for weakly coupled plasmas require modifications. The Maxwell-Boltzmann distribution, expressed in terms of the screened ionic potential, provides a simple way to correct for the density change. Several adjustments of the distribution are considered, including the nonlinear shielding, the quantum effect, the charge neutrality condition, and electron-electron correlation. The nonlinear coupling is shown to add to the linearly shielded potential a new component with much stronger shielding and generally reduces the strength of the linear potential. A simple model for the density enhancement is then constructed for moderately coupled plasmas, which may be applied to approximately correct the existing rates which were obtained in the weak coupling limit. (C) 2004 Published by Elsevier B.V.