DIRAC–FOCK OSCILLATOR STRENGTHS FOR E1 TRANSITIONS IN THE SODIUM ISOELECTRONIC SEQUENCE (Na I–Ca X)

Siegel, W; Migdałek, J.; Kim, Y.-K.

doi:10.1006/adnd.1997.0769

Cited by 28 publications

(19 citation statements)

References 32 publications

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“…These are means of two results obtained by Froese-Fisher & Tachiev (2011) using different theoretical techniques, and a third theoretical result from Siegel et al (1998). These data should be fairly accurate, as there is very good agreement between the three different theoretical results; one is assigned a rating of "A" and the other four "A+" in NIST, indicating uncertainties typically better than ±0.01 dex.…”

Section: Magnesiumsupporting

confidence: 52%

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The elemental composition of the Sun

Scott

Grevesse

Asplund

et al. 2014

A&A

208

160

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Section: Magnesiumsupporting

confidence: 52%

“…3) Chang & Tang (1990). 4) Mean of Siegel et al (1998) and 2 different calculations by Froese-Fisher & Tachiev (2011). 5) Kurucz (2011).…”

mentioning

confidence: 99%

The elemental composition of the Sun

Scott

Grevesse

Asplund

et al. 2014

A&A

208

160

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“…Oscillator strengths ( f -values) were collected mostly from the NIST database (Ralchenko et al 2010). The original sources of the NIST data are Froese Fischer & Tachiev (2010) [Fro], Chang & Tang (1990) [C-T] Butler et al (1993) [But], Siegel et al (1998) [Sie]. Other sources are Aldenius et al (2007) [Ald], Civiš, S. et al (2013) [Civ] and Kurucz & Peytremann (1975) [K-P].…”

Section: Line Broadeningmentioning

confidence: 99%

Mg line formation in late-type stellar atmospheres

Osorio

Barklem

Lind

et al. 2015

A&A

130

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Context. Magnesium is an element of significant astrophysical importance, often traced in late-type stars using lines of neutral magnesium, which is expected to be subject to departures from local thermodynamic equilibrium (LTE). The importance of Mg, together with the unique range of spectral features in late-type stars probing different parts of the atom, as well as its relative simplicity from an atomic physics point of view, makes it a prime target and test bed for detailed ab initio non-LTE modelling in stellar atmospheres. Previous non-LTE modelling of spectral line formation has, however, been subject to uncertainties due to lack of accurate data for inelastic collisions with electrons and hydrogen atoms. Aims. In this paper we build and test a Mg model atom for spectral line formation in late-type stars with new or recent inelastic collision data and no associated free parameters. We aim to reduce these uncertainties and thereby improve the accuracy of Mg non-LTE modelling in late-type stars.Methods. For the low-lying states of Mg i, electron collision data were calculated using the R-matrix method. Hydrogen collision data, including charge transfer processes, were taken from recent calculations by some of us. Calculations for collisional broadening by neutral hydrogen were also performed where data were missing. These calculations, together with data from the literature, were used to build a model atom. This model was then employed in the context of standard non-LTE modelling in 1D (including average 3D) model atmospheres in a small set of stellar atmosphere models. First, the modelling was tested by comparisons with observed spectra of benchmark stars with well-known parameters. Second, the spectral line behaviour and uncertainties were explored by extensive experiments in which sets of collisional data were changed or removed. Results. The modelled spectra agree well with observed spectra from benchmark stars, showing much better agreement with line profile shapes than with LTE modelling. The line-to-line scatter in the derived abundances shows some improvements compared to LTE (where the cores of strong lines must often be ignored), particularly when coupled with averaged 3D models. The observed Mg emission features at 7 and 12 μm in the spectra of the Sun and Arcturus, which are sensitive to the collision data, are reasonably well reproduced. Charge transfer with H is generally important as a thermalising mechanism in dwarfs, but less so in giants. Excitation due to collisions with H is found to be quite important in both giants and dwarfs. The R-matrix calculations for electron collisions also lead to significant differences compared to when approximate formulas are employed. The modelling predicts non-LTE abundance corrections ΔA(Mg) NLTE−LTE in dwarfs, both solar metallicity and metal-poor, to be very small (of order 0.01 dex), even smaller than found in previous studies. In giants, corrections vary greatly between lines, but can be as large as 0.4 dex. Conclusions. Our results emphasise ...

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“…These calculations reached a fair agreement with experiments, but deviated from some ab initio results. Siegel et al (1998) used a semi-empirical model potential approach to compute electric dipole transition oscil-lator strengths for low-lying transitions in the Na isoelectronic sequence (Na i-Ca x). The core polarization effects were explicitly included in the calculations.…”

Section: Previous Work On Atomic Data For Si III and Si Ivmentioning

confidence: 99%

MCDHF and RCI calculations of energy levels, lifetimes, and transition rates in Si III and Si IV

Atalay

Brage

Jönsson

et al. 2019

A&A

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We present extensive multiconfiguration Dirac-Hartree-Fock and relativistic configuration interaction calculations including 106 states in doubly ionized silicon (Si iii) and 45 states in triply ionized silicon (Si iv), which are important for astrophysical determination of plasma properties in different objects. These calculations represents an important extension and improvement of earlier calculations especially for Si iii. The calculations are in good agreement with available experiments for excitation energies, transition properties, and lifetimes. Important deviations from the NIST-database for a selection of perturbed Rydberg series are discussed in detail.

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DIRAC–FOCK OSCILLATOR STRENGTHS FOR E1 TRANSITIONS IN THE SODIUM ISOELECTRONIC SEQUENCE (Na I–Ca X)

Cited by 28 publications

References 32 publications

The elemental composition of the Sun

The elemental composition of the Sun

Mg line formation in late-type stellar atmospheres

MCDHF and RCI calculations of energy levels, lifetimes, and transition rates in Si III and Si IV

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DIRAC–FOCK OSCILLATOR STRENGTHS FOR E1 TRANSITIONS IN THE SODIUM ISOELECTRONIC SEQUENCE (Na I–Ca X)

Cited by 28 publications

References 32 publications

The elemental composition of the Sun

The elemental composition of the Sun

Mg line formation in late-type stellar atmospheres

MCDHF and RCI calculations of energy levels, lifetimes, and transition rates in Si III and Si IV

Contact Info

Product

Resources

About

MCDHF and RCI calculations of energy levels, lifetimes, and transition rates in Si III and Si IV