The properties of a bound electron system immersed in a plasma environment are strongly modified by the surrounding plasma. The modification of an essential quantity, the ionization energy, is described by the electronic and ionic self-energies including dynamical screening within the framework of the quantum statistical theory. Introducing the ionic dynamical structure factor as the indicator for the ionic microfield, we demonstrate that ionic correlations and fluctuations play a critical role in determining the ionization potential depression. This is in particular true for mixtures of different ions with large mass and charge asymmetry. The ionization potential depression is calculated for dense aluminum plasmas as well as for a CH plasma and compared to the experimental data and more phenomenological approaches used so far.

New facilities explore warm dense matter (WDM) at extreme conditions where the densities are very high (e.g., carbon up to density of 50 g cm −3 ) so that electrons are degenerate even at 100 eV temperature. Whereas in the non-degenerate region correlation effects such as Debye screening and its improvements are relevant for the ionization potential depression (IPD), new effects have to be considered in degenerate plasmas. In addition to the Fock shift of the self-energies, the boundstate Pauli blocking becomes important with increasing density. Taking these degeneracy effects into account leads to a reduction of the ionization potential and to a higher degree of ionization. Standard approaches to IPD such as Stewart-Pyatt and widely used opacity tables (e.g., OPAL) do not contain Pauli blocking effects for bound states so that they fail to explain experiments with WDM in the high density region. As example, results for the ionization degree of carbon plasmas are presented.

Theoretical modeling of ionization potential depression (IPD) and the related ionization equilibrium in dense plasmas, in particular, in warm/hot dense matter, represents a significant challenge due to ionic coupling and electronic degeneracy effects. Based on the dynamical structure factor (SF), a quantum statistical model for IPD in multi-ionic plasmas is developed, where quantum exchange and dynamical correlation effects in plasma environments are consistently and systematically taken into account in terms of the concept of self-energy. Calculations for IPD values of different chemical elements are performed with the electronic and ionic SFs. The ionic SFs are determined by solving the Ornstein–Zernike equation in combination with the hypernetted-chain closure relation. As a further application of our approach, we present results for the charge state distribution of aluminum plasmas at several temperatures and densities through solving the coupled Saha equations.

We derive a quantum master equation for an atom coupled to a heat bath represented by a charged particle many-body environment. In Born-Markov approximation, the influence of the plasma environment on the reduced system is described by the dynamical structure factor. Expressions for the profiles of spectral lines are obtained. Wave packets are introduced as robust states allowing for a quasi-classical description of Rydberg electrons. Transition rates for highly excited Rydberg levels are investigated. A circular-orbit wave packet approach has been applied, in order to describe the localization of electrons within Rydberg states. The calculated transition rates are in a good agreement with experimental data.PACS number(s): 03.65. Yz, 32.70.Jz, 32.80.Ee, 52.25.Tx arXiv:1601.04086v1 [physics.atom-ph] 15 Jan 2016 c e c n c = 0. In the bath, in general, the formation of bound states such as atoms is also possible. Furthermore, the interaction of the atom is mediated by the Maxwell field which contains, besides the Coulomb interaction with the charged particles, also single-particle states, the photons. The total system is then described by the Hamiltonian