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The multi-configuration Dirac-Hartree-Fock method and active space approach are used to investigate the energy levels, hyperfine structure constants, and transition probabilities of a neutral silicon atom. The contributions of Breit interactions and quantum electrodynamics correction are considered. Compared with other theoretical and experimental values of energy levels, our values are in good agreement; the discrepancies of the majority of energy levels calculated are within 1% of experimental values, and the energy levels calculated are very close to other theoretical values. The number of energy levels we considered is larger than that of any other theoretical calculations. The values of the hyperfine structure constant A of the radioactive 29Si atom that we calculated are in good agreement with experimental values. From these results we can predict the hyperfine structure constant A of other states of 29Si where no other theoretical results are available. The transition probabilities of neutral silicon have also been calculated and discussed. [ABSTRACT FROM AUTHOR]

Precision study of few-electron, high-Z ions is a privileged field for probing high-field, bound-state quantum electrodynamics (BSQED). However, the accuracy of such tests is plagued by nuclear uncertainties, which are often larger than the BSQED effects under investigation. We propose an alternative method with exotic atoms and show that transitions may be found between circular Rydberg states where nuclear contributions are vanishing while BSQED effects remain large. When probed with newly available quantum sensing detectors, these systems offer gains in sensitivity of 1 to 2 orders of magnitude, while the mean electric field largely exceeds the Schwinger limit. [ABSTRACT FROM AUTHOR]

The fully relativistic multiconfiguration Dirac-Fock (MCDF) method is employed to calculate the excitation energies and wavelengths for nine isoelectronic sequences of tungsten ions. In calculations, electron correlations, quantum electrodynamical (QED) effect, and Breit correction are taken into account. The core-valence and valence-valence corrections are analyzed in a systematic way. The core setting was systematically studied for four cases of one electron occupying the outermost s orbital, one electron occupying the outermost p orbital, three electrons occupying the outermost p orbital, and one electron occupying the outermost d orbital. In our research, at least two calculation models are adopted for every tungsten ion. Through analyzing our results, it is found that the following three calculation models can help to get results closer to measured values: ( i) setting the closed shells as core; ( ii) taking core-valence corrections into account when there is only one valence electron; ( iii) taking valence-valence corrections into account when the number of valence electrons is not less than three. The purpose of this paper is to provide some references on configuration selection and configuration interaction in calculations for a multi-electron system of highly charged tungsten ions. [ABSTRACT FROM AUTHOR]

Wavelengths, transition probabilities, and oscillator strengths have been calculated for M-shell electric dipole transitions in Co-, Ni-, Cu-, Zn-, Ga-, Ge-, and Se-like Au ions. The fully relativistic multiconfiguration Dirac–Fock method, taking quantum electrodynamical effects and the Breit correction into account, was used in the calculations. Calculated energy levels of M-shell excited states for Cu-, Zn-, Ga-, Ge-, and Se-like Au ions from the method were compared with available theoretical and experimental results, and good agreement with them was achieved. [ABSTRACT FROM AUTHOR]