Ionization potential depression model with the influence of neighboring ions for warm/hot and dense plasma

TL;DR

This paper develops an advanced ionization potential depression (IPD) model that accounts for neighboring ions' influence in warm/hot dense plasmas, improving accuracy in predicting plasma ionization states and matching experimental data.

Contribution

It introduces a new IPD model incorporating neighboring ions' effects on screening and ionization, extending previous atomic state dependent models.

Findings

Model agrees well with experimental data for Al, Mg, and Si plasmas.

Neighboring ions significantly affect IPD in warm/hot dense plasma conditions.

Extended model improves understanding of plasma ionization balance.

Abstract

For warm or hot and dense plasma, ionization potential depression plays a crucial role in determining the ionization balance and understanding the resulting microscopic plasma properties. However, the applicability of the widely used IPD models is currently limited under WDP conditions, where the influence of neighboring ions on IPD becomes nonnegligible. Neighboring ions can directly influence the screening potential around the target ion, which then changes the ionization potential. Furthermore, similar to solid-state systems, outer atomic orbitals expand into continuous energy bands due to the existence of neighboring ions, and electrons in these continuous bands can travel from target ion into neighboring ions and become delocalized. As a result, even for their total energy E<0, electrons excited into these continuous bands can be considered ionized, and the ionization conditions differ from those in isolated situations. In our previous work with an atomic state dependent screening model, we included the influence of temporarily recombined electron distributions due to inelastic collision processes between plasma electrons and ions, and evident contributions from these electrons to the screening potential were found under WDP conditions. We now further incorporate the direct contributions of neighboring ions to both screening potentials and ionization conditions. This extended framework reveals that the contribution from neighboring ions substantially influences IPD in WDP. The developed model demonstrates good agreement with experiments for Al, Mg, and Si plasmas with a wide range of 70 to 700 eV temperatures and 1 to 3 times the solid density as well as the hollow Al ions measured in the experiment.