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Pehlivan Rhodin, A., Hartman, H., Nilsson, H. & Jönsson, P. (2024). Accurate and experimentally validated transition data for Si I and Si II. Astronomy and Astrophysics, 682, Article ID A184.
Open this publication in new window or tab >>Accurate and experimentally validated transition data for Si I and Si II
2024 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 682, article id A184Article in journal (Refereed) Published
Abstract [en]

Aims. The aim of this study is to provide radiative data for neutral and singly ionised silicon, in particular for the first experimental oscillator strengths for near-infrared Si I lines. In addition, we aim to perform atomic structure calculations both for neutral and singly ionised silicon while including lines from highly excited levels.

Methods. We performed large-scale atomic structure calculations with the relativistic multiconfiguration Dirac-Hartree-Fock method using the GRASP2K package to determine log(𝑔ƒ) values of Si I and Si II lines, taking into account valence-valence and core-valence electron correlation. In addition, we derived oscillator strengths of near-infrared Si I lines by combining the experimental branching fractions with radiative lifetimes from our calculations. The silicon plasma was obtained from a hollow cathode discharge lamp, and the intensity-calibrated high-resolution spectra between 1037 and 2655 nm were recorded by a Fourier transform spectrometer.

Results. We provide an extensive set of accurate experimental and theoretical log(𝑔ƒ) values. For the first time, we derived 17 log(𝑔ƒ) values of Si I lines in the infrared from experimental measurements. We report data for 1500 Si I lines and 500 Si II lines. The experimental uncertainties of our ƒ-values vary between 5% for the strong lines and 25% for the weak lines. The theoretical log(𝑔ƒ) values for Si I lines in the range 161 nm to 6340 nm agree very well with the experimental values of this study and complete the missing transitions involving levels up to 3s23p7s (61 970 cm−1). In addition, we provide accurate calculated log(𝑔ƒ) values of Si II lines from the levels up to 3s27f (122 483 cm−1) in the range 81 nm to 7324 nm.

Place, publisher, year, edition, pages
EDP Sciences, 2024
Keywords
atomic data, methods: laboratory: atomic, methods: numerical, techniques: spectroscopic
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:mau:diva-66915 (URN)10.1051/0004-6361/202245686 (DOI)001178184800003 ()2-s2.0-85186144682 (Scopus ID)
Available from: 2024-04-25 Created: 2024-04-25 Last updated: 2024-04-25Bibliographically approved
Burheim, M., Hartman, H. & Nilsson, H. (2023). Experimental oscillator strengths of Al I lines for near-infrared astrophysical spectroscopy. Astronomy and Astrophysics, 672, Article ID A197.
Open this publication in new window or tab >>Experimental oscillator strengths of Al I lines for near-infrared astrophysical spectroscopy
2023 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 672, article id A197Article in journal (Refereed) Published
Abstract [en]

Context. Elemental abundances can be determined from stellar spectra, making it possible to study galactic formation and evolution. Accurate atomic data is essential for the reliable interpretation and modeling of astrophysical spectra. In this work, we perform laboratory studies on neutral aluminium. This element is found, for example, in young, massive stars and it is a key element for tracing ongoing nucleosynthesis throughout the Galaxy. The near-infrared (NIR) wavelength region is of particular importance, since extinction in this region is lower than for optical wavelengths. This makes the NIR wavelength region a better probe for highly obscured regions, such as those located close to the Galactic center.

Aims. We investigate the spectrum of neutral aluminium with the aim to provide oscillator strengths (f-values) of improved accuracy for lines in the NIR and optical regions (670–4200 nm).

Methods. Measurements of high-resolution spectra were performed using a Fourier transform spectrometer and a hollow cathode discharge lamp. The f-values were derived from experimental line intensities combined with published radiative lifetimes.

Results. We report oscillator strengths for 12 lines in the NIR and optical spectral regions, with an accuracy between 2 and 11%, as well as branching fractions for an additional 16 lines.

 

Place, publisher, year, edition, pages
EDP Sciences, 2023
Keywords
atomic data, methods: laboratory: atomic, techniques: spectroscopic
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:mau:diva-60505 (URN)10.1051/0004-6361/202245394 (DOI)000976785300010 ()2-s2.0-85156225882 (Scopus ID)
Funder
Swedish Research Council, 2016-04185
Available from: 2023-06-12 Created: 2023-06-12 Last updated: 2023-10-26Bibliographically approved
Hartman, H., Burheim, M., Nilsson, H., Li, W. & Jönsson, P. (2021). Laboratory Atomic Astrophysics for near-infrared Stellar Spectroscopy. In: : . Paper presented at The 20.5th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun (CS20.5).
Open this publication in new window or tab >>Laboratory Atomic Astrophysics for near-infrared Stellar Spectroscopy
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2021 (English)Conference paper, Poster (with or without abstract) (Other academic)
Abstract [en]

Astronomical infrared observations are of increasing importance for stellar spectroscopy. The analysis of element abundance relies on high-quality observations, stellar models, and ultimately on accurate atomic data. With the growing number of near-IR astronomical observations and surveys, the absence of highaccuracy data is becoming apparent and a severe limiting factor.We run a program to take up the task to provide evaluated, high-accuracy atomic data for important transitions in the near-infrared spectral region, mainly 1-5 microns. A combinations of both experimental and theoretical techniques is used, to provide complete sets of data with a low uncertainty. FTS measurements of a discharge are combined with laser induced fluorescence techniques, and GRASP2k and ATSP2k atomic structure calculations for the theoretical values.

National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:mau:diva-47283 (URN)10.5281/zenodo.4564259 (DOI)
Conference
The 20.5th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun (CS20.5)
Projects
https://mau.se/forskning/projekt/experimental-and-computational-atomic-astrophysics/
Funder
Swedish Research Council, 2016-04185
Available from: 2021-12-07 Created: 2021-12-07 Last updated: 2023-10-26Bibliographically approved
Nilsson, H., Engström, L., Lundberg, H., Hartman, H., Palmeri, P. & Quinet, P. (2019). Experimental and theoretical lifetimes and transition probabilities for spectral lines in Nb II (ed.). Astronomy and Astrophysics, 627, Article ID A102.
Open this publication in new window or tab >>Experimental and theoretical lifetimes and transition probabilities for spectral lines in Nb II
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2019 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 627, article id A102Article in journal (Refereed) Published
Abstract [en]

Aims. We have measured and calculated lifetimes of high lying levels in Nb II, and derived absolute transition probabilities by combining the lifetimes with experimental branching fractions. Methods. The lifetimes were measured using time-resolved laser-induced fluorescence in a two-photon and two-step excitation scheme. The branching fractions were measured in intensity calibrated spectra from a hollow cathode discharge, recorded with a Fourier transform spectrometer. The calculations were performed with the relativistic Hartree-Fock method including core polarization. Results. We report experimental lifetimes of 13 levels in the 4d(3)(F-4)5d and 4d(3)(F-4)6s subconfigurations, at an energy around 70 000 cm(-1). By combining the lifetimes with experimental branching fractions absolute transition probabilities of 59 lines are derived. The experimental results are compared with calculated values.

Place, publisher, year, edition, pages
EDP Sciences, 2019
Keywords
atomic data, methods: laboratory: atomic, techniques: spectroscopic
National Category
Natural Sciences
Identifiers
urn:nbn:se:mau:diva-2463 (URN)10.1051/0004-6361/201935614 (DOI)000474334300003 ()2-s2.0-85069513869 (Scopus ID)30119 (Local ID)30119 (Archive number)30119 (OAI)
Available from: 2020-02-27 Created: 2020-02-27 Last updated: 2023-11-01Bibliographically approved
Nilsson, H., Andersson, J., Engström, L., Lundberg, H. & Hartman, H. (2019). Experimental transition probabilities for 4p-4d spectral lines in V II (ed.). Astronomy and Astrophysics, 622, Article ID A154.
Open this publication in new window or tab >>Experimental transition probabilities for 4p-4d spectral lines in V II
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2019 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 622, article id A154Article in journal (Refereed) Published
Abstract [en]

Aims. We aim to measure lifetimes of levels belonging to the 3d(3)(F-4)4d subconfiguration in V II, and derive absolute transition probabilities by combining the lifetimes with experimental branching fractions. Methods. The lifetimes were measured using time-resolved laser-induced fluorescence in a two-photon excitation scheme. The branching fractions were measured in intensity calibrated spectra from a hollow cathode discharge lamp, recorded with a Fourier transform spectrometer. Results. We report lifetimes for 13 levels at an energy around 73 000 cm(-1). Absolute transition probabilities of 78 lines are derived by combining the lifetimes and branching fractions. The experimental values are compared with theoretical data from the literature.

Place, publisher, year, edition, pages
EDP Sciences, 2019
Keywords
atomic data, line: identification, methods: laboratory: atomic, techniques: spectroscopic
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:mau:diva-2356 (URN)10.1051/0004-6361/201834795 (DOI)000458360400001 ()2-s2.0-85061742278 (Scopus ID)29443 (Local ID)29443 (Archive number)29443 (OAI)
Available from: 2020-02-27 Created: 2020-02-27 Last updated: 2023-11-01Bibliographically approved
Pehlivan-Rhodin, A., Hartman, H., Nilsson, H. & Jönsson, P. (2017). Experimental and theoretical oscillator strengths of Mg i for accurate abundance analysis (ed.). Astronomy and Astrophysics, 598(A102), Article ID A102.
Open this publication in new window or tab >>Experimental and theoretical oscillator strengths of Mg i for accurate abundance analysis
2017 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 598, no A102, article id A102Article in journal (Refereed) Published
Abstract [en]

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 -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 di erent 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 Mgi 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 Mgi optical triplet lines (3p 3Po0;1;2 - 4s 3S1), 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 Mgi optical triplet line (3p 3Po0 ;1;2 - 4s 3S1) oscillator strength values are 0.08 dex larger than the previous measurements.

Place, publisher, year, edition, pages
EDP Sciences, 2017
Keywords
atomic data, laboratory methods, spectroscopic techniques, oscillator strengths
National Category
Natural Sciences
Identifiers
urn:nbn:se:mau:diva-16046 (URN)10.1051/0004-6361/201629849 (DOI)000394465000101 ()2-s2.0-85012225001 (Scopus ID)23700 (Local ID)23700 (Archive number)23700 (OAI)
Available from: 2020-03-30 Created: 2020-03-30 Last updated: 2024-04-25Bibliographically approved
Pehlivan Rhodin, A., Belmonte, T., Engström, L., Lundberg, H., Nilsson, H., Hartman, H., . . . Palmeri, P. (2017). Lifetime measurements and oscillator strengths insingly ionized scandium and the solar abundance of scandium (ed.). Monthly notices of the Royal Astronomical Society, 472(3), 3337-3353
Open this publication in new window or tab >>Lifetime measurements and oscillator strengths insingly ionized scandium and the solar abundance of scandium
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2017 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 472, no 3, p. 3337-3353Article in journal (Refereed) Published
Abstract [en]

The lifetimes of 17 even-parity levels (3d5s, 3d4d, 3d6s, and 4p$^2$) in the region 57743-77837 cm$^{-1}$ of singly ionised scandium (\ion{Sc}{ii}) were measured by two-step time-resolved laser induced fluorescence spectroscopy. Oscillator strengths of 57 lines from these highly excited upper levels were derived using a hollow cathode discharge lamp and a Fourier transform spectrometer. In addition, Hartree--Fock calculations where both the main relativistic and core-polarisation effects were taken into account were carried out for both low- and high-excitation levels. There is a good agreement for most of the lines between our calculated branching fractions and the measurements of Lawler and Dakin (1989) in the region 9000-45000 cm$^{-1}$ for low excitation levels and with our measurements for high excitation levels in the region 23500-63100 cm$^{-1}$. This, in turn, allowed us to combine the calculated branching fractions with the available experimental lifetimes to determine semi-empirical oscillator strengths for a set of 380 E1 transitions in \ion{Sc}{ii}. These oscillator strengths include the weak lines that were used previously to derive the solar abundance of scandium. The solar abundance of scandium is now estimated to $\log~\epsilon_\odot = 3.04\pm0.13$ using these semi-empirical oscillator strengths to shift the values determined by Scott et al. (2015). The new estimated abundance value is in agreement with the meteoritic value ($\log~\epsilon_{\text{met}}=3.05\pm0.02$) of Lodders et al. (2009).

Place, publisher, year, edition, pages
Oxford University Press, 2017
Keywords
atomic data, methods laboratory atomic, methods numerical, sun abundances, techniques spectroscopic
National Category
Natural Sciences
Identifiers
urn:nbn:se:mau:diva-16090 (URN)10.1093/mnras/stx2159 (DOI)000413088400067 ()2-s2.0-85052299320 (Scopus ID)24057 (Local ID)24057 (Archive number)24057 (OAI)
Available from: 2020-03-30 Created: 2020-03-30 Last updated: 2024-04-25Bibliographically approved
Palmeri, P., Quinet, P., Lundberg, H., Engström, L., Nilsson, H. & Hartman, H. (2017). Lifetime measurements using two-step laser excitation for high-lying even-parity levels and improved theoretical oscillator strengths in Y II (ed.). Monthly notices of the Royal Astronomical Society, 471(1), 532-540
Open this publication in new window or tab >>Lifetime measurements using two-step laser excitation for high-lying even-parity levels and improved theoretical oscillator strengths in Y II
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2017 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 471, no 1, p. 532-540Article in journal (Refereed) Published
Abstract [en]

We report new time-resolved laser-induced fluorescence lifetime measurements for 22 highly excited even-parity levels in singly ionized yttrium (Y II). To populate these levels belonging to the configurations 4d6s, 5s6s 4d5d, 5p2, 4d7s and 4d6d, a two-step laser excitation technique was used. Our previous pseudo-relativistic Hartree–Fock model (Bi´emont et al. 2011) was improved by extending the configuration interaction up to n = 10 to reproduce the new experimental lifetimes. A set of semi-empirical oscillator strengths extended to transitions falling in the spectral range λλ194–3995 nm, depopulating these 22 even-parity levels in Y II, is presented and compared to the values found in the Kurucz’s data base (Kurucz 2011).

Place, publisher, year, edition, pages
Oxford University Press, 2017
Keywords
atomic data, atomic processes, methods: numerical, methods: experimental
National Category
Natural Sciences
Identifiers
urn:nbn:se:mau:diva-2447 (URN)10.1093/mnras/stx1619 (DOI)000408211700033 ()2-s2.0-85052536714 (Scopus ID)24058 (Local ID)24058 (Archive number)24058 (OAI)
Available from: 2020-02-27 Created: 2020-02-27 Last updated: 2024-02-06Bibliographically approved
Hartman, H., Engström, L., Lundberg, H., Nilsson, H., Quinet, P., Fivet, V., . . . Blagoev, K. (2017). Radiative data for highly excited 3d84d levels in Ni II from laboratory measurements and atomic calculations (ed.). Astronomy and Astrophysics, 600, Article ID A108.
Open this publication in new window or tab >>Radiative data for highly excited 3d84d levels in Ni II from laboratory measurements and atomic calculations
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2017 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 600, article id A108Article in journal (Refereed) Published
Abstract [en]

Aims: This work reports new experimental radiative lifetimes and calculated oscillator strengths for transitions from 3d84d levels of astrophysical interest in singly ionized nickel. Methods: Radiative lifetimes of seven high-lying levels of even parity in Ni II (98 400-100 600 cm-1) have been measured using the time-resolved laser-induced fluorescence method. Two-step photon excitation of ions produced by laser ablation has been utilized to populate the levels. Theoretical calculations of the radiative lifetimes of the measured levels and transition probabilities from these levels are reported. The calculations have been performed using a pseudo-relativistic Hartree-Fock method, taking into account core polarization effects. Results: A new set of transition probabilities and oscillator strengths has been deduced for 477 Ni II transitions of astrophysical interest in the spectral range 194-520 nm depopulating even parity 3d84d levels. The new calculated gf-values are, on the average, about 20% higher than a previous calculation and yield lifetimes within 5% of the experimental values.

Place, publisher, year, edition, pages
EDP Sciences, 2017
Keywords
atomic data, methods laboratory atomic, techniques spectroscopic
National Category
Natural Sciences
Identifiers
urn:nbn:se:mau:diva-15980 (URN)10.1051/0004-6361/201629615 (DOI)000400754000073 ()2-s2.0-85017395371 (Scopus ID)24063 (Local ID)24063 (Archive number)24063 (OAI)
Available from: 2020-03-30 Created: 2020-03-30 Last updated: 2024-02-05Bibliographically approved
Quinet, P., Fivet, V., Palmeri, P., Engström, L., Hartman, H., Lundberg, H. & Nilsson, H. (2016). Experimental radiative lifetimes for highly excited states and calculated oscillator strengths for lines of astrophysical interest in singly ionized cobalt (Co II) (ed.). Monthly notices of the Royal Astronomical Society, 462(4), 3912-3917
Open this publication in new window or tab >>Experimental radiative lifetimes for highly excited states and calculated oscillator strengths for lines of astrophysical interest in singly ionized cobalt (Co II)
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2016 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 462, no 4, p. 3912-3917Article in journal (Refereed) Published
Abstract [en]

This work reports new experimental radiative lifetimes and calculated oscillator strengths for transitions of astrophysical interest in singly ionized cobalt. More pre- cisely, nineteen radiative lifetimes in Co+ have been measured with the time-resolved laser-induced fluorescence technique using one- and two-step excitations. Out of these, seven belonging to the high lying 3d7(4F)4d configuration in the energy range 90697 - 93738 cm 1 are new, and the other twelve from the 3d7(4F)4p configuration with energies between 45972 and 49328 cm 1 are compared with previous measurements. In addition, a relativistic Hartree-Fock model including core-polarization e ects has been employed to compute transition rates. Supported by the good agreement between theory and experiment for the lifetimes, new reliable transition probabilities and os- cillator strengths have been deduced for 5080 Co ii transitions in the spectral range 114- 8744 nm.

Place, publisher, year, edition, pages
Oxford University Press, 2016
Keywords
atomic data, atomic processes
National Category
Natural Sciences
Identifiers
urn:nbn:se:mau:diva-16059 (URN)10.1093/mnras/stw1900 (DOI)000385231600033 ()2-s2.0-84994479817 (Scopus ID)21247 (Local ID)21247 (Archive number)21247 (OAI)
Available from: 2020-03-30 Created: 2020-03-30 Last updated: 2023-10-27Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-0375-6076

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