Pressure ionization in partition function algebra

The phrase “Pressure Ionization” stands for the progressive disappearance, delocalization or hybridization of bound orbitals of atoms immersed in high-density plasmas. In the ion cell framework, Pressure Ionization is already partly included as orbitals disappear above some density when the one electron energies turn positive or, equivalently, when the average orbital radius becomes larger than the ion cell radius. However, this simple description yields a non-physical steep variation of the average charge, 〈Z〉, when an entire electron shell vanishes at once. To overcome this problem, several authors proposed the introduction of a “pressure ionized effective statistical weights” g∗ = g × π∗ in order to obtain a smooth disappearance of the orbitals. On the other hand, super-configurations and partition functions algebra have been introduced by Bar-Shalom et al. for a statistical, but detailed, description of multi-electron, multi-ionized atoms. In this paper, a method that merges pressure ionization and partition functions algebra is proposed. We also elucidate why both ionization potential lowering and reduction of statistical weights have to be introduced and provide some first results.