Thermodynamic properties and the ionization potential lowering of excited ions in hot and dense plasmas

The present paper is divided into two sections. First, a new cylindrically symmetric atomic model is introduced to describe the influence of the plasma environment on the thermodynamic and atomic properties of ions immersed in hot and dense plasmas (see also Ref. 1, heretoforth referred to as I). In the present paper the authors focus on the description of the basic assumptions of the model and its predictions on the thermodynamic properties, whereas in a subsequent paper this same model is used to calculate the plasma effects on the atomic properties and the emission spectra. Second, this model is used to find the distribution function of the ionization potential lowering imposed on a given ion, the average ionization potential lowering in the plasma and the standard deviation of its fluctuations. The general aim of the model is to account for the distortion of the local microfield on the peripheries of an ion from a spherical to cylindrical symmetry due to the influence of the nearest neighbor. The model is expected to give a more realistic description of the local microfield than spherically symmetric models. In particular, it can describe the nonspherical distortion of the electronic wavefunctions, and the related phenomena, which cannot be described in terms of spherically symmetric models. Moreover, these properties are calculated as function of the distance to the nearest neighbor, thereby providing the tools to calculate not only the average values of the various parameters but their distribution functions as well