Quantum-mechanical calculation of ionization potential lowering in dense plasmas

Abstract

The charged environment within a dense plasma leads to the phenomenon of ionization potential depression (IPD) for ions embedded in the plasma. Accurate predictions of the IPD effect are of crucial importance for modeling atomic processes occurring within dense plasmas. Several theoretical models have been developed to describe the IPD effect, with frequently discrepant predictions. Only recently, first experiments on IPD in Al plasma have been performed with an x-ray free-electron laser (XFEL), where their results were found to be in disagreement with the widely-used IPD model by Stewart and Pyatt. Another experiment on Al, at the Orion laser, showed disagreement with the model by Ecker and Kröll. This controversy shows a strong need for a rigorous and consistent theoretical approach to calculate the IPD effect. Here we propose such an approach: a two-step Hartree-Fock-Slater model. With this parameter-free model we can accurately and efficiently describe the experimental Al data and validate the accuracy of standard IPD models. Our model can be a useful tool for calculating atomic properties within dense plasmas with wide-ranging applications to studies on warm dense matter, shock experiments, planetary science, inertial confinement fusion and studies of non-equilibrium plasmas created with XFELs.

13 pages, 9 figures, to be published in Phys. Rev. X; added references [46,47]

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• Energy loss and friction characteristics of electrons at warm dense matter and non-ideal dense plasma conditions
• Nuclear Excitation by Electron Capture in Excited Ions
• Monte-Carlo approach to calculate the ionization of warm dense matter within particle-in-cell simulations
• First-principles derivation and properties of density-functional average-atom models
• Improved calculations of mean ionization states with an average-atom model
• Transient ionization potential depression in nonthermal dense plasmas at high x-ray intensity
• Investigating Mechanisms of State Localization in Highly-Ionized Dense Plasmas
• Dense plasma opacity via the multiple-scattering method
• A molecular-dynamics approach for studying the non-equilibrium behavior of x-ray-heated solid-density matter
• Predicting Excitation Energies in Warm Dense Matter
• Theoretical investigation of orbital alignment of x-ray-ionized atoms in exotic electronic configurations
• Charge State Distributions in Dense Plasmas
• Impact of free electron degeneracy on collisional rates in plasmas
• Average-atom treatment of relaxation time in X-ray Thomson scattering from warm-dense matter
• Compton spectra of atoms at high x-ray intensity
• Average Atom Model with Siegert States
• Decreasing ultrafast X-ray pulse durations with saturable absorption and resonant transitions