Ionization potential depression in dense iron plasmas near solid density

Abstract

In a dense hot plasma, the energy levels of an embedded ion are lowered by the induced screening potential, which is termed as the ionization potential depressions (IPDs) for the continuum levels. Recent experiments on the precision measurements of the IPDs in solid-density plasmas made it feasible to validate the widely used models. Yet, to date, most of the renewed experimental and theoretical verifications were focused on the low Z dense plasmas. In this work, the IPDs of heavier Fe plasmas were studied near solid density using a recently developed self-consistent temperature dependent ion-sphere model. The present results show reasonable agreement with the b4-potential method at some densities and temperatures, yet there exist large discrepancies between our predicted IPDs and those by the widely used simple closed analytical models. Namely, for Fe plasmas in a density range of 1–16 g cm−3 and a temperature range of 100–1000 eV, a simplified modification of Ecker–Kröll model predicts a much higher IPD than our model, whereas the Stewart–Pyatt, the ion-sphere, and the Debye–Hückel models predict much lower IPDs, which indicates the need of further study on the plasma screening potential. The results obtained in this work should be helpful for the astrophysical and inertial-fusion applications where the IPDs are vital parameters in determining the ionization balance.