Effect of the ionization potential depression on electron-impact ionization cross-sections in dense plasmas

The modeling of the emission and absorption spectra of hot dense plasmas out of local thermodynamic equilibrium requires accurate calculations of the cross-sections of the different radiative and collisional processes. In this work, we focus on the electron-impact ionization (EII). As the EII cross-section depends strongly on the ionization energy, and since this energy is very sensitive to the plasma environment, we need to account for plasma density effects such as the ionization potential depression (IPD). The IPD can be calculated by using the formulas of Stewart and Pyatt or Ecker and Kröll. A recent model, based on the classical molecular dynamics method, was developed at Aix-Marseille University. It simulates multi-component plasmas, and accounts for all the charge correlations, providing a distribution of ionization energies for each ion charge. This distribution is a result of the fluctuations of the environment. In this work, we compare calculated IPDs to experimental results obtained at LCLS (Stanford). Following a recent work, we discuss the distribution of the ionization energy in an aluminum plasma, and propose an alternative definition of the cross-section.