Infrared transitions and oscillator strengths of Ca and Mg

Civiš, Svatopluk; Ferus, Martin; Chernov, V. E.; Zanozina, E. M.

doi:10.1051/0004-6361/201321052

Cited by 21 publications

(8 citation statements)

References 34 publications

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“…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]. For the Mg i IR lines with no data found in the literature we calculated the f -values using the hydrogenic formula from Guseinov & Mamedov (2012) [Hydro].…”

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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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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“…They used the close-coupling approximation with the R-matrix technique. Moreover, Civiš et al (2013) performed oscillator strength calculations using the quantum defect theory (QDT) in the region of 800-9000 cm −1 . Froese Fischer et al (2006) performed calculations using the multi configuration Hartree-Fock method.…”

Section: Introductionmentioning

confidence: 99%

Experimental and theoretical oscillator strengths of Mg i for accurate abundance analysis

Rhodin

Hartman

Nilsson

et al. 2017

A&A

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Context. With the aid of stellar abundance analysis, it is possible to study the galactic formation and evolution. Magnesium is an important element to trace the α-element evolution in our Galaxy. For chemical abundance analysis, such as magnesium abundance, accurate and complete atomic data are essential. Inaccurate atomic data lead to uncertain abundances and prevent discrimination between different evolution models. Aims. We study the spectrum of neutral magnesium from laboratory measurements and theoretical calculations. Our aim is to improve the oscillator strengths ( f -values) of Mg i lines and to create a complete set of accurate atomic data, particularly for the near-IR region.Methods. We derived oscillator strengths by combining the experimental branching fractions with radiative lifetimes reported in the literature and computed in this work. A hollow cathode discharge lamp was used to produce free atoms in the plasma and a Fourier transform spectrometer recorded the intensity-calibrated high-resolution spectra. In addition, we performed theoretical calculations using the multiconfiguration Hartree-Fock program ATSP2K.Results. This project provides a set of experimental and theoretical oscillator strengths. We derived 34 experimental oscillator strengths. Except from the Mg i optical triplet lines (3p 3 P• 0,1,2 -4s 3 S 1 ), these oscillator strengths are measured for the first time. The theoretical oscillator strengths are in very good agreement with the experimental data and complement the missing transitions of the experimental data up to n = 7 from even and odd parity terms. We present an evaluated set of oscillator strengths, gf, with uncertainties as small as 5%. The new values of the Mg i optical triplet line (3p 3 P• 0,1,2 -4s 3 S 1 ) oscillator strength values are ∼0.08 dex larger than the previous measurements.

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“…According to our earlier work (Civiš et al 2012a,b,c,e;2013a, 2014, the most prominent lines in this domain are due to transitions between the g-, h-, or i-Rydberg states, which are neither reported on in the literature nor listed in the atomic databases. Our aim is to present new knowledge on these high-l Ne i states.…”

Section: Introductionmentioning

confidence: 85%

FTIR laboratory measurement of Ne i Rydberg states in 1.43−14.3μm spectral range

Kubelík

Civiš

Pastorek

et al. 2015

A&A

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Context. The Ne i spectrum in the 800−1800 cm −1 (5.55−14.3 μm) domain has not been previously investigated.Aims. To address this spectral gap, we performed high-resolution laboratory measurements of the Ne i emission spectrum over the 800−7000 cm −1 (1.43−14.3 μm) range.Methods. The Ne i laboratory spectra were obtained from a pulsed discharge plasma and recorded using time-resolved Fourier transform spectroscopy. The identification of the spectral lines was performed according to the transition probability values calculated using the quantum defect method.Results. Based on these measurements, we report the wavenumbers of 151 Ne i lines and energy values for 14 Ne i levels that are not listed in the available databases.

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Infrared transitions and oscillator strengths of Ca and Mg

Cited by 21 publications

References 34 publications

Mg line formation in late-type stellar atmospheres

Mg line formation in late-type stellar atmospheres

Experimental and theoretical oscillator strengths of Mg i for accurate abundance analysis

FTIR laboratory measurement of Ne i Rydberg states in 1.43−14.3μm spectral range

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