As the plasma coupling constant g increases, new phenomena start to become appreciable, such as the nonlinear Debye shielding and crystallization. Modelling such plasmas require re-evaluation of atomic reaction rates, most of which have been calculated in the weak coupling limit. In particular, the electron density near the central ion is enhanced, and the rates must reflect this change. However, this is a difficult and time-consuming task, because the distribution function is no longer coordinate independent, as in the free particle Maxwell distribution. For a moderately coupled plasma (MCP) roughly with the coupling constant less than one, it may be possible to develop a simplified procedure to treat this problem. We present a model that may be used to approximately adjust the existing rates evaluated with the free distribution, by multiplying them with the electron density enhancement (EDE) factors, which are presumably dependent on the particular processes involved. The EDE may be estimated by the solution of the collisionless Boltzmann equation, which is nonlinearly coupled to the Maxwell-Poisson equation. We first improve the solution by incorporating the nonlinear shielding effect, the quantum effect near the central ion, the charge neutrality constraint, and the electron-electron correlation. We have found that the nonlinear effect adds a component to the potential which is shorter range than the linear shielding case, while the quantum effect largely modifies the potential, and thus the density, in the close vicinity of the central ion. For MCP, even with all the above adjustments, the distribution may still be made separable in the r and v coordinates. The final simplification involves an adoption of the mean value theorem to replace the r-dependent part by a constant, i.e. r→s, which may be regarded as a parameter. This is a drastic step, but allows to retain the conventional rates. For the particular choice s≈a , where a is the electron sphere radius, for example, we have [1] the EDE factor given by R=exp[Zg exp(-3g)^1/2], where g/sT≈1/at , with the temperature T that includes the threshold shift. This is the same form as that discussed in ref. 1 for the radiative recombination process, but is here extended its application to all other processes. It seems to exhibit the correct g dependence of the EDE, but its sensitibity to parameter s is not yet fully determined. With test calculations and further improvements, R may be a viable way to incorporate the EDE for MCP.

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