Atomic Cascade Computations

Abstract

Atomic cascades are ubiquitous in nature and they have been explored within very different scenarios, from precision measurements to the modeling of astrophysical spectra, and up to the radiation damage in biological matter. However, up to the present, a quantitative analysis of these cascades often failed because of their inherent complexity. Apart from utilizing the rotational symmetry of atoms and a proper distinction of different physical schemes, a hierarchy of useful approaches is therefore needed in order to keep cascade computations feasible. We here suggest a classification of atomic cascades and demonstrate how they can be modeled within the framework of the Jena Atomic Calculator. As an example, we shall compute within a configuration-average approach the stepwise decay cascade of atomic magnesium, following a 1s inner-shell ionization, and simulate the corresponding (final) ion distribution. Our classification of physical scenarios (schemes) and the hierarchy of computational approaches are both flexible to further refinements as well as to complex shell structures of the atoms and ions, for which the excitation and decay dynamics need to be modeled in good detail.

Many-Electron QED with Redefined Vacuum Approach

“…In recent years, the accuracy of large-scale correlation calculations of transition energies in many-electron atoms and ions drastically improved [2,44,[53][54][55][56]. Various highly efficient computer codes have been developed for this purpose [57][58][59][60][61][62]. In view of this rapid progress, it becomes increasingly important to include the QED effects in these calculations as well.…”

Many-Electron QED with Redefined Vacuum Approach

“…In recent years, the accuracy of large-scale correlation calculations of transition energies in many-electron atoms and ions drastically improved [2,33,[42][43][44][45]. Various highly efficient computer codes have been developed for this purpose [46][47][48][49][50][51]. In view of this rapid progress, it becomes increasingly important to include the QED effects in these calculations as well.…”

Dielectronic recombination strengths and plasma rate coefficients of multiply charged ions

“…The consequent use of these many-electron amplitudes in the setup of the code distinguishes Jac from most other atomic structure codes that are often based on prior decomposition of these amplitudes into various coefficients and radial integrals, well before any implementation or coding is done. The explicit use of these amplitudes has been found useful also for implementing approximate atomic Green functions (Fritzsche & Surzhykov, 2021) as well as a number of atomic cascades (Fritzsche, Palmeri & Schippers, 2021), such as the step-wise decay following inner-shell excitation or the creation of holes by photoexcitation or photoionization; they will enable us also to treat interference phenomena in the future. In this work, we here expand this concept to the formation and stabilization of doubly excited levels and, hence, to the computation of DR plasma rate coefficients for quite general open-shell structures.…”