Multiconfiguration Dirac-Hartree-Fock Calculations with Spectroscopic Accuracy: Applications to Astrophysics

Abstract

Abstract:Atomic data, such as wavelengths, spectroscopic labels, broadening parameters and transition rates, are necessary for many applications, especially in plasma diagnostics, and for interpreting the spectra of distant astrophysical objects. The experiment with its limited resources is unlikely to ever be able to provide a complete dataset on any atomic system. Instead, the bulk of the data must be calculated. Based on fundamental principles and well-justified approximations, theoretical atomic physics derives and implements algorithms and computational procedures that yield the desired data. We review progress and recent developments in fully-relativistic multiconfiguration Dirac-Hartree-Fock methods and show how large-scale calculations can give transition energies of spectroscopic accuracy, i.e., with an accuracy comparable to the one obtained from observations, as well as transition rates with estimated uncertainties of a few percent for a broad range of ions. Finally, we discuss further developments and challenges.

Discrepancies in Atomic Data and Suggestions for Their Resolutions

“…They have performed systematic calculations with the MCDF and MBPT methods to determine the energy levels and A-values to spectroscopic accuracy. However, for this kind of work very large calculations need to be performed for which Jönsson et al [49] have suggested further modifications to the GRASP2K code. Similarly, Safronova et al [50,51] have performed very accurate (and large) calculations for a series of ions, using the CI+MBPT codes, and with single, double and triple excitations of electrons.…”

Atomic Data for Plasma Spectroscopy: The CHIANTI Database, Improvements and Challenges

“…Multiconfiguration Dirac-Hartree-Fock (MCDHF) calculations with the various improvements (see e.g., [43,44]) of Ian Grant's relativistic atomic structure program GRASP are also available. Data for ions in the C, N, B, O, F, Ne, P, Si, S, Mg, Al isoelectronic sequences are now available, see [45] for a review.…”

“…Uncertainties in the radiative rates (oscillator strengths and A-values) can be assessed by comparing the values in the length and velocity forms [45], or more generally comparing the results of different calculations, as done e.g., for Fe XIII [74] and for N IV [75]. Other useful information is provided by laboratory measurements of radiative lifetimes.…”

Experimental and Theoretical Study of the 5s\(^2\)5p\(^3\) and 5s\(^5\)p\(^4\) Configurations in Sb-like Cerium

“…Relativistic calculations were performed using the GRASP2018 package [6]. Further details of the package can be found elsewhere [10]. Ce VIII calculations have been done parity-wise i.e., even and odd states were determined separately in the extended optimization level (EOL) scheme.…”