MCDHF Calculations and Beam-Foil EUV Spectra of Boron-Like Sodium Ions (Na VII)

Abstract

Atomic data, such as wavelengths and line identifications, are necessary for many applications, especially in plasma diagnostics and for interpreting the spectra of distant astrophysical objects. The number of valence shell electrons increases the complexity of the computational problem. We have selected a five-electron ion, Na 6+(with the boron-like spectrum Na VII), for looking into the interplay of measurement and calculation. We summarize the available experimental work, perform our own extensive relativistic configuration interaction (RCI) computations based on multi-configuration Dirac-Hartree-Fock (MCDHF) wave functions, and compare the results to what is known of the level structure. We then discuss problems with databases that have begun to combine observations and computations.

Extreme-Ultraviolet Beam-Foil Spectra of Na through Cl

“…Compilations and tabulations based on experimental data are always suspected of being incomplete. An effort was therefore undertaken to test this assumption and the quality of modern atomic structure computations [59]. State-of-the-art relativistic configuration interaction (RCI) computations of Na VII (B-like) were to be compared with extended EUV spectra recorded at Bochum.…”

“…Unfortunately this also means that in-spectrum reference lines are available only from the very element under study. The experimental survey spectrum shown in [59] suffers from this problem; the long-wavelength sections of the spectrum (recorded at a different occasion) need to be adjusted in wavelength by an amount different from the short-wavelength section. The spectra shown and discussed below result from improvements beyond the calibration used in the presentation of experimental data in the study by Jönsson et al [59].…”

“…The experimental survey spectrum shown in [59] suffers from this problem; the long-wavelength sections of the spectrum (recorded at a different occasion) need to be adjusted in wavelength by an amount different from the short-wavelength section. The spectra shown and discussed below result from improvements beyond the calibration used in the presentation of experimental data in the study by Jönsson et al [59]. The effort of identifying reference lines and thus tying down the wavelength scale with appropriate accuracy is an ongoing process and has not yet been finished.…”

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

“…To meet this demand, the RMCDHF/RCI and SD-MR calculations for the B-, C-, N-, O-, F-and Ne-like sequences have been extended to hundreds of states in what we refer to as spectrum calculations [45][46][47][48][49][50][51][52]. The range of ions, the targeted configurations and the number of studied states for each sequence are summarized in Table 5.…”

“…The RMCDHF/RCI and SD-MR method has been used to compute tens of thousands of E1, M1, E2, M2 transitions rates for the B-to Si-like sequences [28][29][30][31][32]43,[45][46][47][48][49][50][51][52][54][55][56]. The E1 and E2 rates are internally validated by giving δA/A along with A.…”