Correlation, Breit, and QED effects in spectra of Mg-like ions

Abstract

We calculated spectra of the first six members of the Mg-like isoelectronic sequence using different approximations. The most accurate results were obtained with the configuration interaction + all order method (CI+AO), which provided relative accuracy for transition energies on the level of 0.1%, or better. On this level of accuracy the Breit and QED corrections become important for the systems with nuclear charge Z 20. The retardation part of the Breit interaction and QED corrections for the partial waves with l = 0 are still too small to be important.

Fock-space relativistic coupled-cluster calculation of hyperfine induced $\bf {^1S_0 \rightarrow {^3P^o_0}}$ clock transition in Al$^+$

“…Considering the contributions from the Breit and QED corrections, we observe the largest cumulative contribution of about 0.01% of the total value in the case of 3 P o 0 . This small contribution is in agreement with the previous calculation [29], however, with opposite phase.…”

“…For the other states, errors lie in-between, with the states from configurations 3s 2 and 3s3p more accurate than those from the high energy configurations. Among the previous theory results, the most accurate results are from the CI+AO calculations by Konovalova and collaborators [29] and Safronova and collaborators [11]. The maximum relative error is about 0.14% in each calculations in the case of 3s3d 3 D 2 and 1 P o 1 states, respectively.…”

Configuration Interaction and Many‐Body Perturbation Theory: Application to Scandium, Titanium, and Iodine

“…Because of that, it is more efficient to treat correlations between few valence electrons separately from weaker correlations, which involves core electrons. [3][4][5] However, the size of the valence CI space exponentially grows with the number of valence electrons N v and it becomes impossible to make full CI. This method is realized in the computer package, [2] which can be used to calculate spectra of atoms with several valence electrons and arbitrary number of closed core shells.…”

Precision calculation of energy levels for four-valent Si I

“…During the last two decades this method was used for numerous calculations of many-electron atoms and ions and proved to be very effective for systems with two-three valence electrons (see, e.g. [3,4,5,6]), where this method typically provide an accuracy about 1%, or better. Less often this method was used for systems with four, or more valence electrons [7,8,9,10,11,12] and it is still not clear what accuracy one can expect in this case.…”