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1. Collision-induced satellite in the blue wing of the Balmer-beta line and consequences on the Balmer series

Author: F. Spiegelman, N. F. Allard, J. F. Kielkopf, Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques Laboratoire (LCPQ), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Fédération de recherche « Matière et interactions » (FeRMI), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Institut d'Astrophysique de Paris (IAP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), and University of Louisville
Subjects: molecular data, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Computer Science::Information Retrieval, FOS: Physical sciences, Astrophysics::Solar and Stellar Astrophysics, line: profiles, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Solar and Stellar Astrophysics (astro-ph.SR), white dwarfs
Abstract: In this paper we emphasize the non-Lorentzian behavior of the Balmer series in helium-dominated DBA white dwarf stars for which the decades-old problem exists for the determination of the hydrogen abundance. In a very recent work, we have shown that quasi-molecular line satellites due to H-He and H-H collisions are responsible for the asymmetrical shape of the Lyman-alpha lines observed with the Cosmic Origin Spectrograph (COS) and that a similar asymmetry exists for the Balmer-alpha line profiles. In continuation with very recent work, where the n=2, 3 potential energies and transition dipole moments from the ground state were determined, here, we present accurate H-He potential energies and electronic transition dipole moments concerning the molecular states correlated with H(n=4)+He and their transition dipole moments with the states correlated with H(n=2)+He. Those new data are used to provide a theoretical investigation of the collisional effects in the blue wing of the Balmer-beta line of H perturbed by He. Because of the general trend characterizing the repulsive Sigma states of the potential energies involved in the Balmer series, the amplitude in the core of the line is decreasing very fast with the order of the series when the helium density gets as large as 10^21 cm^-3. This study is undertaken by applying a unified theory of spectral line broadening that is valid at very high helium densities found in DZA white dwarf stars. The treatment includes collision-induced (CI) line satellites due to asymptotically forbidden transitions, and it explains the asymmetry observed in their spectra., 7pages, 8 figures. arXiv admin note: text overlap with arXiv:2201.00878
Published: 2022
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2. Collisional effects in the blue wing of the Balmer-alpha line

Author: S. Bourdreux, John F. Kielkopf, N. F. Allard, Fernand Spiegelman, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Institut d'Astrophysique de Paris (IAP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), University of Louisville, Laboratoire de Chimie et Physique Quantiques Laboratoire (LCPQ), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Fédération de recherche « Matière et interactions » (FeRMI), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), and Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)
Subjects: FOS: Physical sciences, Alpha (ethology), Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, spectrum, symbols.namesake, star, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010306 general physics, white dwarf, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Line (formation), Physics, Wing, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Balmer series, Astronomy and Astrophysics, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, symbols, spectral line
Abstract: In order to investigate the near wing of the Lyman-alpha line, accurate line profile calculations and molecular data are both required due to the existence of a close line satellite responsible for its asymmetrical shape. Lyman-alpha lines observed with the Cosmic Origin Spectograph (COS) on the Hubble Space Telescope ( HST) show this peculiarity in the spectra of DBA and DA white dwarf stars. A similar asymmetrical shape in the blue wing can be predicted in the Balmer-alpha line of H perturbed by He and H atoms. In continuation with a very recent work on the Lyman-alpha line, where the n=2 potential energies and transition dipole moments from the ground state were determined, we present new accurate H-He potential energies and electronic transition dipole moments involving the molecular states correlated with H(n=3)+He and their transition dipole moments with the states correlated with H(n=2)+He. Those new data and existing molecular data for H(n=2,3)-H are used to provide a theoretical investigation of the collisional effects in the blue wing of the Balmer-alpha line of H perturbed by He and H atoms. We note the consequences for the Balmer-alpha line shape in the physical conditions found in the cool atmosphere of DZA white dwarfs where helium densities may be as high as 10^21 cm-3. This study is undertaken with a unified theory of spectral line broadening valid at very high helium densities., 9 pages, 12 figures
Published: 2021
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3. Collisional effects in the blue wing of Lyman-alpha

Author: John F. Kielkopf, N. F. Allard, Fernand Spiegelman, Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques Laboratoire (LCPQ), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Fédération de recherche « Matière et interactions » (FeRMI), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)
Subjects: molecular data, Hydrogen, Atomic Physics (physics.atom-ph), FOS: Physical sciences, chemistry.chemical_element, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Resonance (particle physics), Physics - Atomic Physics, 0103 physical sciences, atomic data, Coulomb, 010306 general physics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), white dwarfs, Line (formation), Physics, White dwarf, Sigma, line: profiles, Astronomy and Astrophysics, Dipole, chemistry, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Atomic physics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Degeneracy (mathematics)
Abstract: Spectral observations below Lyman-α are now obtained with the Cosmic Origin Spectrograph (COS) on the Hubble Space Telescope. It is therefore necessary to provide an accurate treatment of the blue wing of the Lyman-α line that enables correct calculations of radiative transport in DA and DBA white dwarf stars. On the theoretical front, we very recently developed very accurate H-He potential energies for the hydrogen 1s, 2s, and 2p states. Nevertheless, an uncertainty remained about the asymptotic correlation of the Σ states and the electronic dipole transition moments. A similar difficulty occurred in our first calculations for the resonance broadening of hydrogen perturbed by collisions with neutral H atoms. The aim of this paper is twofold. First, we clarify the question of the asymptotic correlation of the Σ states, and we show that relativistic contributions, even very tiny, may need to be accounted for a correct long-range and asymptotic description of the states because of the specific 2s 2p Coulomb degeneracy in hydrogen. This effect of relativistic corrections, inducing small splitting of the 2s and 2p states of H, is shown to be important for the Σ-Σ transition dipole moments in H-He and is also discussed in H-H. Second, we use existent (H-H) and newly determined (H-He) accurate potentials and properties to provide a theoretical investigation of the collisional effects on the blue wing of the Lyman-α line of H perturbed by He and H. We study the relative contributions in the blue wing of the H and He atoms according to their relative densities. We finally achieve a comparison with recent COS observations and propose an assignment for a feature centered at 1190 Å.
Published: 2021
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4. H-He collision-induced satellite in the Lyman alpha profile of DBA white dwarf stars

Author: Grégoire Guillon, John F. Kielkopf, Roberto Linguerri, Majdi Hochlaf, Siyi Xu, Ivan Hubeny, Muneerah Mogren Al Mogren, N. F. Allard, Bilel Mehnen, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Department of Physics and Astronomy [Louisville], University of Louisville, Gemini Observatory, parent, Laboratoire Interdisciplinaire Carnot de Bourgogne [Dijon] (LICB), Université de Bourgogne (UB)-Université de Technologie de Belfort-Montbeliard (UTBM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Instrumentation, Simulation et Informatique Scientifique (COSYS-LISIS), Université Gustave Eiffel, King Saud University [Riyadh] (KSU), and University of Arizona
Subjects: ATOMIC DATA, LINE: PROFILE, Ab initio, chemistry.chemical_element, BASIS-SET, LINE, EXCITED-STATE, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Spectral line, Physics - Atomic Physics, WHITE DWARF, 0103 physical sciences, Radiative transfer, ABSORPTION, Astrophysics::Solar and Stellar Astrophysics, AB-INITIO CALCULATION, Physics::Atomic Physics, ELECTRONIC-TRANSITION MOMENT, 010306 general physics, STARS: ATMOSPHERE, 010303 astronomy & astrophysics, Helium, Line (formation), POTENTIAL-ENERGY CURVE, Physics, [PHYS]Physics [physics], BALMER-ALPHA, White dwarf, Astronomy and Astrophysics, MOLECULAR DATA, Potential energy, Dipole, chemistry, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, ATOMIC PROCESS, SHAPE, [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], Atomic physics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: The spectra of helium-dominated white dwarf stars with hydrogen in their atmosphere present a distinctive broad feature centered around 1160~\AA\/ in the blue wing of the Lyman-$\alpha$ line. It is extremely apparent in WD 1425+540 recently observed with HST COS. With new theoretical line profiles based on ab initio atomic interaction potentials we show that this feature is a signature of a collision-induced satellite due to an asymptotically forbidden transition. This quasi-molecular spectral satellite is crucial to understanding the asymmetrical shape of Lyman-$\alpha$ seen in this and other white dwarf spectra. Our previous work predicting this absorption feature was limited by molecular potentials that were not adequate to follow the atomic interactions with spectroscopic precision to the asymptotic limit of large separation. A new set of potential energy curves and electronic dipole transition moments for the lowest electronic states of the H--He system were developed to account accurately for the behavior of the atomic interactions at all distances, from the chemical regime within 1~\AA\/ out to where the radiating H atoms are not significantly perturbed by their neighbors. We use a general unified theory of collision-broadened atomic spectral lines to describe a rigorous treatment of hydrogen Lyman-$\alpha$ with these potentials and present a new study of its broadening by radiative collisions of hydrogen and neutral helium. These results enable ab initio modeling of radiative transport in DBA white dwarf atmospheres., Comment: 9 pages, 7 figures
Published: 2020
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5. The nearby magnetic cool DZ white dwarf PM J08186-3110

Author: Stephane Vennes, Adela Kawka, Thierry Leininger, N. F. Allard, Florent Xavier Gadéa, International Centre for Radio Astronomy Research (ICRAR), The University of Western Australia (UWA)-Government of Western Australia-Curtin University [Perth], Planning and Transport Research Centre (PATREC)-Planning and Transport Research Centre (PATREC), Mathematical Sciences Institute (MSI), Australian National University (ANU), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Groupe Méthodes et outils de la chimie quantique (LCPQ) (GMO), Laboratoire de Chimie et Physique Quantiques Laboratoire (LCPQ), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Fédération de recherche « Matière et interactions » (FeRMI), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)
Subjects: chemistry.chemical_element, FOS: Physical sciences, Astrophysics, 01 natural sciences, Spectral line, Atmosphere, symbols.namesake, 0103 physical sciences, Dispersion (optics), Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Helium, ComputingMilieux_MISCELLANEOUS, Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Physics, [PHYS]Physics [physics], Zeeman effect, 010308 nuclear & particles physics, Magnesium, White dwarf, Astronomy and Astrophysics, Magnetic field, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, Astrophysics - Solar and Stellar Astrophysics, chemistry, 13. Climate action, Space and Planetary Science, symbols, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: We present an analysis of photometric, spectroscopic and spectropolarimetric data of the nearby, cool, magnetic DZ white dwarf PM J08186-3110. High dispersion spectra show the presence of Zeeman splitted spectral lines due to the presence of a surface average magnetic field of 92 kG. The strong magnesium and calcium lines show extended wings shaped by interactions with neutral helium in a dense, cool helium-rich atmosphere. We found that the abundance of heavy elements varied between spectra taken ten years apart but we could not establish a time-scale for these variations; such variations may be linked to surface abundance variations in the magnetized atmosphere. Finally, we show that volume limited samples reveal that about 40% of DZ white dwarfs with effective temperatures below 7000 K are magnetic., Comment: Accepted for publication in MNRAS
Published: 2020
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6. Blue line wings of resonance lines of potassium and sodium perturbed by molecular hydrogen and rare gases

Author: Grégoire Guillon, J. F. Kielkopf, H. Berriche, V. A. Alekseev, F. Spiegelman, N. F. Allard, University of Louisville, Institut d'Astrophysique de Paris (IAP), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), St Petersburg State University (SPbU), Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC), Université de Bourgogne (UB), Université de Monastir - University of Monastir (UM), American University of Ras Alkhaimah (AURAK), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)
Subjects: History, 010304 chemical physics, Chemistry, Potassium, Sodium, Hydrogen molecule, Inorganic chemistry, Resonance, chemistry.chemical_element, 01 natural sciences, Computer Science Applications, Education, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, 0103 physical sciences, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, Line (formation)
Abstract: International audience
Published: 2017
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7. New study of the line profiles of sodium perturbed by H2

Author: Thierry Leininger, Fernand Spiegelman, P. Mollière, N. F. Allard, Institut d'Astrophysique de Paris (IAP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Groupe Méthodes et outils de la chimie quantique (LCPQ) (GMO), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse)
Subjects: profiles, molecular data, Opacity, Brown dwarf, FOS: Physical sciences, Astrophysics, 01 natural sciences, Spectral line, Atmosphere, Planet, 0103 physical sciences, Hot Jupiter, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Line (formation), Earth and Planetary Astrophysics (astro-ph.EP), Physics, 010304 chemical physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astronomy and Astrophysics, Exoplanet, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, brown dwarfs, Astrophysics - Earth and Planetary Astrophysics
Abstract: The opacity of alkali atoms, most importantly of Na and K, plays a crucial role in the atmospheres of brown dwarfs and exoplanets. We present a comprehensive study of Na–H2 collisional profiles at temperatures from 500 to 3000 K, the temperatures prevailing in the atmosphere of brown dwarfs and Jupiter-mass planets. The relevant H2 perturber densities reach several 1019 cm−3 in hot (Teff ≳ 1500 K) Jupiter-mass planets and can exceed 1020 cm−3 for more massive or cooler objects. Accurate pressure-broadened profiles that are valid at high densities of H2 should be incorporated into spectral models. Unified profiles of sodium perturbed by molecular hydrogen were calculated in the semi-classical approach using up-to-date molecular data. New Na–H2 collisional profiles and their effects on the synthetic spectra of brown dwarfs and hot Jupiters computed with petitCODE are presented.
Published: 2019
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8. Study of the parameters of the He(3 3S)-He(2 3P) line *

Author: N. F. Allard, Nelly Bonifaci, and André Denat
Subjects: Materials science, chemistry, Excited state, Optical physics, chemistry.chemical_element, Emission spectrum, Plasma, Atomic physics, Atomic and Molecular Physics, and Optics, Spectral line, Helium, Corona discharge, Line (formation)
Abstract: We have observed emission spectrum in dense plasmas of helium excited by a corona discharge at 706.69 nm. In continuation of an analysis of spectra obtained in gaseous helium at 300 K, we report on a study of the line parameters of the observed spectra. We discuss the major importance of temperature and perturber density in the broadening, shift and asymmetry measured from calculated profiles within a unified line shape semi-classical theory. The comparison is done with existing data derived from experimental spectra at 300 K. The theoretical work is extended at lower temperatures down to 40 K.
Published: 2011
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9. K–H 2 line shapes for the spectra of cool brown dwarfs

Author: John F. Kielkopf, N. F. Allard, Fernand Spiegelman, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut d'Astrophysique de Paris (IAP), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Department of Physics and Astronomy [Louisville], University of Louisville, Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)
Subjects: Physics, Opacity, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Brown dwarf, Resonance, Astronomy and Astrophysics, Astrophysics, Effective temperature, Stellar classification, 01 natural sciences, Spectral line, Space and Planetary Science, Planet, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 010306 general physics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Line (formation), line: profiles / brown dwarfs
Abstract: International audience; Observations of cooler and cooler brown dwarfs show that the contribution from broadening at many bars pressure is becoming important. The opacity in the red optical to near-IR region under these conditions is dominated by the extremely pressure-broadened wings of the alkali resonance lines, in particular, the K I resonance doublet at 0.77 µm. Collisions with H 2 are preponderant in brown dwarf atmospheres at an effective temperature of about 1000 K; the H 2 perturber densities reach several 10 19 even in Jupiter-mass planets and exceed 10 20 for super-Jupiters and older Y dwarfs. As a consequence, it appears that when the far wing absorption due to alkali atoms in a dense H 2 atmosphere is significant, accurate pressure broadened profiles that are valid at high densities of H 2 should be incorporated into spectral models.
Published: 2016
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10. Theoretical profiles of the Mg + resonance lines perturbed by collisions with He

Author: N. F. Allard, John F. Kielkopf, Grégoire Guillon, V. A. Alekseev, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut d'Astrophysique de Paris (IAP), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Laboratoire Interdisciplinaire Carnot de Bourgogne (LICB), Université de Bourgogne (UB)-Centre National de la Recherche Scientifique (CNRS), St Petersburg State University (SPbU), University of Louisville, Galaxies, Etoiles, Physique, Instrumentation ( GEPI ), Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université Paris Diderot - Paris 7 ( UPD7 ) -Centre National de la Recherche Scientifique ( CNRS ), Institut d'Astrophysique de Paris ( IAP ), Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire Interdisciplinaire Carnot de Bourgogne ( LICB ), Université de Bourgogne ( UB ) -Centre National de la Recherche Scientifique ( CNRS ), St Petersburg State University ( SPbU ), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB)
Subjects: Opacity, [ PHYS.ASTR ] Physics [physics]/Astrophysics [astro-ph], Ab initio, chemistry.chemical_element, Astrophysics, 01 natural sciences, Resonance (particle physics), Metal, 0103 physical sciences, stars: atmospheres, Astrophysics::Solar and Stellar Astrophysics, 010306 general physics, 010303 astronomy & astrophysics, Helium, Astrophysics::Galaxy Astrophysics, Line (formation), white dwarfs, Physics, Stellar atmosphere, White dwarf, Astronomy and Astrophysics, line: profiles, chemistry, 13. Climate action, Space and Planetary Science, visual_art, visual_art.visual_art_medium, Astrophysics::Earth and Planetary Astrophysics, Atomic physics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: International audience; The effects of collision broadening by He are central to understanding the opacity of cool stellar atmospheres. Aims. DZ white dwarfs show metal lines which are, in many cases, believed to come from some rocky material, a remnant of a former exoplanetary system. The analysis of the Mg + resonance lines is a valuable method to determine the chemical abundances in these systems. Methods. Unified profiles of the strongest of the UV lines of Mg + have been calculated in the semi-classical approach using very recent ab initio potential energies. Results. We present the first theoretical line profile calculations of the resonance lines of Mg + that have been perturbed by helium in physical conditions of atmospheres in helium-rich white dwarfs with metal traces.
Published: 2016
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11. K–H2 quasi-molecular absorption detected in the T-dwarf $\mathsf{\varepsilon}$ Indi Ba

Author: F. Allard, N. F. Allard, D. Homeier, J. Kielkopf, M. J. McCaughrean, and F. Spiegelman
Subjects: Physics, Photosphere, Brown dwarf, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Spectral line, Atmosphere, Gravitation, 13. Climate action, Space and Planetary Science, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 010306 general physics, Absorption (electromagnetic radiation), 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Line (formation), Visible spectrum
Abstract: T-type dwarfs present a broad and shallow absorption feature centred around 6950 A in the blue wing of the K doublet at 0.77 micron which resembles in depth and shape the satellite absorption predicted by detailed collisional broadening profiles. In our previous work, the predicted line satellite position was however somewhat too blue compared to the observed feature. In this paper we investigate whether new calculations of the energy surfaces of the potentials in the K-H_2 system, including spin-orbit coupling, result in a closer coincidence of the satellite with the observed position. We also investigate the extent to which CaH absorption bands contribute to the feature. We present model atmospheres and synthetic spectra, including gravitational settling for an improved description of depth-dependent abundances of refractory elements, and based on new K-H_2 line profiles using improved interaction potentials. By comparison with a high signal-to-noise optical spectrum of the T1 dwarf epsilon Indi Ba, we find that these new models do reproduce the observed feature, while CaH does not contribute for the atmospheric parameters considered. We also find that CaH is settled out so deep into the atmosphere that even turbulent vertical mixing would appear insufficient to bring significant amounts of CaH to the photosphere in dwarfs later than ~L5. We conclude that previous identification of the feature at this location in T and late L dwarf spectra with CaH was erroneous, as expected on physical grounds: calcium condenses onto grains in early L dwarfs and thus should have settled out of the photosphere in cooler brown dwarfs. This finding revokes one observational verification for the cloud-clearing theory: a gradual clearing of the cloud cover in early T dwarfs.
Published: 2007
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12. Laboratory Detection of the Lyβ 1150 Å Quasi-molecular Satellite Seen in Far Ultraviolet Spectroscopic Explorer Observations of the White Dwarf G226-29

Author: N. F. Allard, J. Huber, John F. Kielkopf, Department of Physics, University of Louisville, Institut d'Astrophysique de Paris (IAP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), and Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics, Hydrogen, Absorption spectroscopy, Stellar atmosphere, Astronomy, White dwarf, chemistry.chemical_element, Astronomy and Astrophysics, Molecular orbital theory, Plasma, Astrophysics, Spectral line, chemistry, Space and Planetary Science, Astrophysics::Solar and Stellar Astrophysics, Physics::Atomic Physics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Absorption (electromagnetic radiation)
Abstract: International audience; We report a laboratory measurement of the 1150 Å collision-induced quasi-molecular satellite of Lybeta. It was first identified in Far Ultraviolet Spectroscopic Explorer observations of the cool DA white dwarf G226-29. The satellite, predicted by theoretical calculations of the complete profile of the hydrogen Lyalpha and Lybeta lines, arises from transitions occurring during close collisions of hydrogen atoms. Fits of model atmospheres with these profiles to observed spectra provide accurate constraints on stellar temperature and gravity. The comparison here of the far-ultraviolet absorption spectrum of a laser-produced hydrogen plasma with the theoretical absorption profiles and a model of the plasma confirms the underpinning atomic and molecular theory.
Published: 2004
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13. Far Ultraviolet Spectroscopic ExplorerObservation of the Ultramassive White Dwarf PG 1658+441

Author: J. Dupuis, Pierre Chayer, Guillaume Hébrard, Stephane Vennes, N. F. Allard, Institut d'Astrophysique de Paris (IAP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), and Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS)
Subjects: Stars: Individual: Alphanumeric: PG 1658+441, Physics, Stars: White Dwarfs, Solar mass, Far ultraviolet, Line: Profiles, Balmer series, White dwarf, Stars: Abundances, Astronomy and Astrophysics, Astrophysics, symbols.namesake, [SDU]Sciences of the Universe [physics], Space and Planetary Science, symbols, Fuse (electrical), Satellite, Ultraviolet: Stars
Abstract: International audience; We present an analysis of the Far Ultraviolet Spectroscopic Explorer (FUSE) spectrum of the ultramassive (M=1.31 Msolar), magnetic (Bs=2.3 MG) white dwarf PG 1658+441. The far-ultraviolet (FUV) spectrum exhibits very broad Lyman lines and quasi-molecular Lyβ satellites, but weak Lyγ satellites may also be present. PG 1658+441 is the hottest white dwarf known to show these satellite features. We fit the Lyman lines with stellar models and obtain atmospheric parameters consistent with a published analysis of the Balmer lines. By averaging results obtained for the different FUSE segments, we determine Teff=29,620+/-500 K and logg=9.31+/-0.07. The models match the data over large portions of the spectrum, but discrepancies remain near the satellite features. Finally, no trace elements have been identified in the FUV spectrum, and we provide abundance upper limits for C, N, Si, and P.
Published: 2003
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14. Study of the far wing of the Balmer α line of hydrogen perturbed by collisions with protons

Author: N. F. Allard, John F. Kielkopf, and A. Decrette
Subjects: Physics, Electron density, Hydrogen, chemistry.chemical_element, Balmer series, Hydrogen atom, Atomic and Molecular Physics, and Optics, Spectral line, Spectral line shape, Ion, symbols.namesake, chemistry, symbols, Physics::Atomic Physics, Atomic physics, Nuclear Experiment, Line (formation)
Abstract: The theory of the Balmer α line of atomic hydrogen perturbed by collisions with protons predicts quasi-molecular satellites in the line wing due to H-H+ collisions. Measurements of the spectrum of a laser-produced plasma confirm the existence of the strongest of these features.
Published: 2002
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15. Blue satellites on He lines due to He-He collisions

Author: Benjamin Deguilhem, Florent Xavier Gadéa, John F. Kielkopf, Antonio Monari, N. F. Allard, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Institut d'Astrophysique de Paris (IAP), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Groupe Méthodes et outils de la chimie quantique (LCPQ) (GMO), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)
Subjects: Physics, [PHYS]Physics [physics], media_common.quotation_subject, Stellar atmosphere, Astronomy and Astrophysics, Astrophysics, Stellar classification, 01 natural sciences, Potential energy, Asymmetry, Spectral line, Wavelength, Space and Planetary Science, 0103 physical sciences, [CHIM]Chemical Sciences, Stellar structure, 010306 general physics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, Line (formation), media_common
Abstract: The shape and broadening of He lines affects radiative transport in dense, He-rich, stellar atmospheres. At wavelengths inaccessible for direct observation, we rely on theoretical calculations of self-broadening to support stellar structure and spectral modeling. In this work, we examine lines of He due to 1s–2p and 2p–3s transitions. The line profiles are analyzed in terms of a unified theory of spectral line broadening using ab initio potential energies that have been recently determined. For temperatures up to 20 000 K, the linear dependence of width and shift on gas density and the non-linear dependence on temperature of the Lorentzian core of the resonance line are described. Beyond the conventional symmetrical Lorentzian core, we show that they are asymmetrical and have significant additional contributions on the short wavelength side. This blue asymmetry is a consequence of maxima in the corresponding He2 potential energy difference curves at short and intermediate internuclear distance. Over a limited range of density and temperature, laboratory measurements in the visible and near infrared can be used to validate the potentials that underlie the spectral line profile theory, which is useful for modeling spectra over the extreme ranges of temperature and density encountered in stellar and planetary atmospheres.
Published: 2013
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16. Absorption spectra of Na atoms in dense He

Author: John F. Kielkopf, Frank Stienkemeier, N. F. Allard, Fernand Spiegelman, Akira Nakayama, Institut d'Astrophysique de Paris (IAP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)
Subjects: [PHYS]Physics [physics], Materials science, Absorption spectroscopy, Ab initio, chemistry.chemical_element, 01 natural sciences, Atomic and Molecular Physics, and Optics, Spectral line, chemistry, 0103 physical sciences, Atom, Physics::Atomic and Molecular Clusters, Atomic physics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010306 general physics, 010303 astronomy & astrophysics, Quasistatic process, Path integral Monte Carlo, Helium, Line (formation)
Abstract: International audience; We present an analysis of Na-He collisional profiles at high density and very low temperature in a unified line shape semi-classical theory which contains the impact as well the quasistatic limits. Clearly understanding the variation of shape of the two fine-structure components of the 3s−3p line with increasing helium density allows us to understand experimental spectra of a Na atom attached to He nanodroplets. We compare our collisional approach to path integral Monte Carlo calculations using the same ab initio Na-He molecular potentials.
Published: 2013
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17. Study of absorption on the wings of sodium resonance line perturbed by molecular hydrogen

Author: Fernand Spiegelman, N. F. Allard, V. A. Alekseev, Institut d'Astrophysique de Paris (IAP), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)
Subjects: History, Chemistry, Sodium, Brown dwarf, Ab initio, chemistry.chemical_element, 01 natural sciences, Exoplanet, Computer Science Applications, Education, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Atomic physics, 010306 general physics, Absorption (electromagnetic radiation), Unified field theory, 010303 astronomy & astrophysics, Resonance line, Line (formation)
Abstract: International audience; The unified theory line profiles for neutral Na perturbed by H2 are obtained using new set of ab initio potentials calculated for several collision geometries. The results are of interest for modeling exoplanet and brown dwarf atmospheres.
Published: 2012
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18. Comparative Study of Emission Spectra of He(3S)-He(2P) at 706 and 728 nm Due to the Triplet and Singlet Transitions

Author: Florent Xavier Gadea, Antonio Monari, N. F. Allard, Benjamin Deguilhem, Institut d'Astrophysique de Paris (IAP), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Groupe Méthodes et outils de la chimie quantique (LCPQ) (GMO), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)
Subjects: History, Work (thermodynamics), Chemistry, 0103 physical sciences, Emission spectrum, Singlet state, Atomic physics, 010306 general physics, 010303 astronomy & astrophysics, 01 natural sciences, Computer Science Applications, Education, Line (formation)
Abstract: International audience; This study of the self-broadening of the 728 nm He line is performed in order to establish similarities and differences to the self-broadening of the triplet 3s-2p line at 706 nm. In a previous work we presented the first calculations of He-He collisional profiles at 706nm due to the triplet 3s-2p transition in a unified line shape semi-classical theory using ab-initio molecular potentials. The excellent agreement between experimental and theoretical determinations of the near wing of the line profiles established the accuracy of the interaction potentials. New ab-initio potentials for the singlet 3s-2p transitions allow us to extend our previous study to the line at 728 nm.
Published: 2012
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19. Multiple perturber effects in the far red wing of Lyman α line

Author: N. F. Allard, J. F. Kielkopf, Marco Antonio Gigosos, and Manuel Ángel González
Subjects: Physics, Wing, Autocorrelation, Brown dwarf, Astrophysics::Solar and Stellar Astrophysics, White dwarf, Far-red, Astrophysics, Effective temperature, Blue dwarf, Black dwarf
Abstract: A small fraction of the DA white dwarf are known to have rather low effective temperature. It is of considerable interest to determine line profiles in these extreme physical conditions. In such cool white dwarfs the perturber density is so high that the one perturber approximation breaks down and the collisional effects must be treated by using the autocorrelation formalism in order to take account the simultaneous collisions with more than one perturbing atom.
Published: 2008
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20. New line profiles of sodium and potassium perturbed by helium for brown dwarf and very cool white dwarf stars

Author: M. Christova, N. F. Allard, J. F. Kielkopf, D. Homeier, F. Allard, Marco Antonio Gigosos, Manuel Ángel González, Department of Applied Physics, Technical University of Sofia, Institut d'Astrophysique de Paris (IAP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Physique stellaire et galactique, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Department of Physics and Astronomy, University of Louisville, Leibniz-Institut für Astrophysik Potsdam (IAP), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Gigosos, Marco Antonio, Gonzalez, and Manuel Angel
Subjects: Physics, Sodium, Potassium, Hydrogen molecule, Brown dwarf, chemistry.chemical_element, Astronomy, White dwarf, Astrophysics, Stellar classification, chemistry, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Blue dwarf, Astrophysics::Galaxy Astrophysics, Helium
Abstract: International audience; The optical spectra of L- and T-type dwarfs exhibit a continuum dominated by the far wings of the absorption profiles of the Na 3s-3p and K 4s-4p doublet perturbed by molecular hydrogen and helium. We report on our work on new calculations of line profiles of Na and K perturbed by He for the conditions prevailing in brown dwarf atmospheres and very cool white dwarfs.
Published: 2008
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21. Balmer α and Lyman β Emitted by a Laser-Produced Plasma

Author: J. F. Kielkopf and N. F. Allard
Subjects: symbols.namesake, Chemistry, Pinch, symbols, Balmer series, Plasma diagnostics, Electron, Plasma, Atomic physics, Spectral line, Order of magnitude, Line (formation)
Abstract: A laser‐produced plasma in hydrogen is being used to study the shift, shape and width of the Balmer α and Lyman β spectral lines emitted by the n = 3 state of atomic hydrogen perturbed by H+ and electrons. Recent measurements at densities up to 1020 cm−3 show that the Balmer α center shifts monotonically to the red with increasing density. The largest shifts seen, of the order of 200 A, occur with shift‐to‐width ratios of up to 0.25. At densities below 1019 cm−3 the shift‐to‐width ratio is an order of magnitude smaller, in agreement with published gas‐liner pinch plasma experiments, but the laser‐plasma explores an order of magnitude higher density. The broad core profiles are consistent with unified line shape theory calculations based on exact H2+ potentials. Balmer α exhibits satellites, some of which are close to the unperturbed line center, and are expected to influence the shift and shape of the line at high H+ density. The satellites may influence the line shift at the highest densities observed. L...
Published: 2002
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22. A collision-induced satellite in the Lyman Beta profile due to H-H collisions

Author: Peter Schmelcher, I. Drira, John F. Kielkopf, and N. F. Allard
Subjects: Physics, Chemical Physics (physics.chem-ph), Hydrogen, Energetic neutral atom, Atomic Physics (physics.atom-ph), Stellar atmosphere, chemistry.chemical_element, FOS: Physical sciences, Plasma, Astrophysics::Cosmology and Extragalactic Astrophysics, Physics - Plasma Physics, Atomic and Molecular Physics, and Optics, Physics - Atomic Physics, Ion, Plasma Physics (physics.plasm-ph), Physics - Atmospheric and Oceanic Physics, Electric dipole moment, chemistry, Physics - Chemical Physics, Beta (plasma physics), Atmospheric and Oceanic Physics (physics.ao-ph), Physics::Atomic Physics, Atomic physics, Line (formation)
Abstract: We present a theoretical profile of the Lyman Beta line of atomic hydrogen perturbed by collisions with neutral hydrogen atoms and protons. We use a general unified theory in which the electric dipole moment varies during a collision. A collision-induced satellite appears on Lyman Beta, correlated to the B''\barB 1Sigma+u - X 1Sigma+g asymptotically forbidden transition of H_2. As a consequence, the appearance of the line wing between Lyman Alpha and Lyman Beta is shown to be sensitive to the relative abundance of hydrogen ions and neutral atoms, and thereby to provide a temperature diagnostic for stellar atmospheres and laboratory plasmas., Comment: 8 pages, 4 figures, acc.f.publ.European Physical Journal D
Published: 2000
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23. The ZZ Ceti instability strip revisited

Author: N. F. Allard and Detlev Koester
Subjects: Physics, Space and Planetary Science, Astronomy, QB1-991, Astronomy and Astrophysics, Astrophysics, Instability strip
Published: 2000
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24. Effect of the variation of electronic dipole moment on theoretical spectra: application to the λ Bootis stars

Author: M. Gerbaldi, R. Faraggiana, N. F. Allard, I. Drira, R. Kurucz, and John F. Kielkopf
Subjects: Physics, Dipole, Stars, Moment (physics), Radiative transfer, Stellar atmosphere, Astrophysical plasma, Astrophysics, Atomic physics, Variation (astronomy), Spectral line
Published: 1999
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25. Quasi-molecular satellites in the Lyman β profile: application to the white dwarf stars

Author: N. F. Allard, John F. Kielkopf, and I. Drira
Subjects: Physics, Astronomy, White dwarf, Astrophysical plasma, Astrophysics, Massive compact halo object, Stellar classification
Published: 1999
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26. Lyman series profiles: From laser-plasmas to white dwarf stars

Author: N. F. Allard and J. F. Kielkopf
Subjects: Physics, Lyman series, Transition dipole moment, White dwarf, Astronomy, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Spectral line, Stars, symbols.namesake, Radiative transfer, symbols, Astrophysics::Solar and Stellar Astrophysics, Astrophysical plasma, Physics::Atomic Physics, Emission spectrum, Astrophysics::Galaxy Astrophysics
Abstract: The low energy interactions of neutral and ionized hydrogen atoms are fundamental processes which also have important applications to the diagnostics of laboratory and astrophysical plasmas. Satellites in the far wings of Lyman α and Lyman β have been identified as ultraviolet absorption features in the spectra of white dwarf and λ Bootis stars, and they are seen in the emission spectra of plasmas produced when a pulsed laser excites a target H2 gas. The observed Lyman series profiles agree with unified line shape theory which includes variation of the dipole transition moment during the radiative collision.
Published: 1999
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27. Emission profiles of K-He exciplexes in cold helium gas

Author: N F Allard
Subjects: History, Range (particle radiation), Helium gas, chemistry.chemical_element, Alkali metal, Computer Science Applications, Education, chemistry, Excited state, Atom, Physics::Atomic and Molecular Clusters, Physics::Atomic Physics, Emission spectrum, Atomic physics, Helium, Line (formation)
Abstract: Emission spectra of exciplexes composed of a light alkali atom in the first excited state and 4He atoms have been observed in cryogenic gas in the spectral range from the atomic D lines to 6300 cm−1. A unified semi-classical theory of line broadening has been used to determine the total profile from the center to the far wings of emission profiles of potassium perturbed by helium at low temperatures and high He density. The agreement of the theoretical peak positions of K*Hen exciplexes compared to the experimental determinations is fairly good. Such comparisons provide a critical test of the calculated molecular potentials and the relevance of the theoretical approach which has been used.
Published: 2012
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28. Physical interpretation of the blue shift of spectra obtained by corona discharge in liquid helium

Author: N F Allard
Subjects: History, Work (thermodynamics), Chemistry, Liquid helium, Spectral line, Computer Science Applications, Education, Blueshift, law.invention, law, Electric discharge, Atomic physics, Quasistatic process, Corona discharge, Line (formation)
Abstract: We discuss the major importance of temperature and perturber density in the broadening and shift of the He 706 nm triplet 3s-2p transition within a unified line shape semi-classical theory which contains the impact as well the quasistatic limits. In a previous paper we presented the first calculations of He-He collisional profiles for this transition using ab-initio molecular potentials. The excellent agreement between our theoretical determination of the near wing of the line profiles and reported experimental spectra of a corona discharge in gaseous He at 300 K established the validity of our interpretation of the spectra and the accuracy of the interaction potentials. In liquid He, the experimental line profiles are formed under conditions where two or more perturbers are likely to act simultaneously. Such phenomena determine the character of a spectral line at high perturber density. In this work we show that it is possible to determine the physical conditions of temperature and pressure from the experimental spectra of an electric discharge in liquid He. We show that at 4 K the theoretical line shift is negative in disagreement with an incorrect analysis reported in a recent paper and also presented at this conference.
Published: 2012
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29. Theoretical and laboratory spectra of sodium perturbed by molecular hydrogen

Author: J. P. Beaulieu, John F. Kielkopf, Giovanna Tinetti, N. F. Allard, Fernand Spiegelman, Institut d'Astrophysique de Paris (IAP), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), University College of London [London] (UCL), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)
Subjects: Physics, Opacity, Extrapolation, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Resonance (particle physics), Spectral line, Dipole, Orders of magnitude (time), Space and Planetary Science, 0103 physical sciences, Radiative transfer, Astrophysics::Earth and Planetary Astrophysics, Atomic physics, 010306 general physics, 010303 astronomy & astrophysics, Line (formation)
Abstract: International audience; We present new unified theory line profiles of neutral Na perturbed by H2. We used a priori Na-H2 potentials, transition dipole moments and validated pseudo-potentials as input to the line shape, and evaluated the profiles for temperatures and densities appropriate for modeling exoplanet and brown dwarf atmospheres. The theory for the resonance lines was compared with new laboratory spectra of sodium to test the validity of the potentials and resulting profiles. The Lorentzian function commonly used to approximate a collisional line profile in radiative transfer calculations is shown to be inadequate, except within a few halfwidths of the line center. In the far wing, the opacity caused by collisions may be several orders of magnitude greater than the extrapolation of the Lorentzian core.
Published: 2012
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30. Profiles for density and temperature dependence of the far red wing of the Lyman α line compared

Author: J F Kielkopf and N F Allard
Subjects: Physics, History, Opacity, White dwarf, medicine.disease_cause, Spectral line, Computer Science Applications, Education, Dipole, medicine, Radiative transfer, Astrophysics::Solar and Stellar Astrophysics, Singlet state, Atomic physics, Unified field theory, Ultraviolet
Abstract: A reliable determination of the line profiles of atomic hydrogen for physical conditions of cool white dwarfs requires a unified theory which takes into account both the singlet and triplet transitions contributing to Lyman alpha using accurate interaction potentials and radiative dipole transition moments. We show that multiple perturber effects have to be considered using the autocorrelation formalism. A comparison with experimental laboratory spectra of cool dense plamas also shows that indeed multiple H-perturbers are an important influence in the far wing extending to 3000 A in the ultraviolet. Under cool dense white dwarf atmosphere conditions, multiple perturber collisions for the singlet states contribute more to the ultraviolet opacity than binary collisions of the triplet states.
Published: 2009
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31. Optical and Ultraviolet Analyses of ZZ Ceti Stars and Study of the Atmospheric Convective Efficiency in DA White Dwarfs

Author: Robert Lamontagne, Pierre Bergeron, F. Wesemael, Gilles Fontaine, N. F. Allard, and Rex A. Saffer
Subjects: Physics, Stars, Space and Planetary Science, K-type main-sequence star, Flare star, White dwarf, Astronomy, Astronomy and Astrophysics, Astrophysics, Massive compact halo object, Stellar classification, Blue dwarf, Main sequence
Published: 1995
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32. Observation of the Simultaneous Additive Effect of Several Xenon Perturbers on the Cs6s−9pDoublet

Author: J. F. Kielkopf and N. F. Allard
Subjects: Physics, Xenon, Absorption spectroscopy, chemistry, General Physics and Astronomy, Order (ring theory), chemistry.chemical_element, Absorption (logic), Atomic physics
Abstract: Multiple satellites appear in absorption spectra on both components of the Cs $6s\ensuremath{-}9p$ doublet perturbed by xenon at densities of the order of ${10}^{19}$ atoms/${\mathrm{cm}}^{3}$. The profiles of these perturbed lines computed with the Anderson-Talman theory, and the density dependence of the absorption at the multiple satellite frequencies, definitely identify the origin of the satellites as the combined additive effect of one to four perturbers.
Published: 1979
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33. Determination of Cs(np)-Xe interactions from spectral line profile measurements

Author: J F Kielkopf and N F Allard
Subjects: Physics, Spectrometer, business.industry, media_common.quotation_subject, chemistry.chemical_element, Asymmetry, Atomic and Molecular Physics, and Optics, Spectral line, symbols.namesake, Optics, Xenon, chemistry, Fourier analysis, Caesium, symbols, Atomic physics, business, Doppler effect, media_common, Line (formation)
Abstract: The 6s-7p, 8p and 9p absorption transitions in caesium perturbed by xenon foreign gas at a temperature of approximately 500K and densities up to 1.2*1019 atoms/cm3 have been observed with a high-resolution computer-controlled spectrometer. A Fourier analysis technique to deconvolve the asymmetric line core from instrumental and Doppler effects yields width, shift and asymmetry for the 7p an 8p doublets independent of the instrument and directly comparable with line-broadening calculations. Normalised profiles of the wings of the 7p and 8p transitions, and of the entire 9p contour are also given from measurements at sufficiently high resolution that instrumental effects are negligible. The observed line core-parameters and line profiles are compared with Anderson-Talman lineshape calculations (1956). The authors also note the observation of multiple-perturber satellites as predicted by the Anderson-Talman theory based on the assumption of additivity of the interaction.
Published: 1980
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34. Alkali-rare-gas line profiles in a square-well potential approximation. I. Satellites

Author: N F Allard
Subjects: Rare gas, Physics, Amplitude, Position (vector), Autocorrelation, Finite potential well, Emission spectrum, Atomic physics, Alkali metal, Atomic and Molecular Physics, and Optics, Line (formation)
Abstract: The profiles of the emission lines of Cs perturbed by Xe have been calculated using Anderson and Talman theory (1956). A square-well potential has been chosen which provides an analytical autocorrelation function that allows a great number of precise and fast calculations. Periodic red satellites centred at multiples of the depth of the well, have been found. The variations of their amplitude and position with density and the parameters of the potential are investigated. The present paper is restricted to the study of the satellites but their influence on the main line parameters will be developed in a further paper.
Published: 1978
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35. Unified theory of collisional line profiles: study of the D lines of caesium perturbed by xenon: width, shift, asymmetry and satellites

Author: Y D Biraud, N F Allard, and S Sahal-Brechot
Subjects: Physics, media_common.quotation_subject, chemistry.chemical_element, Asymmetry, Atomic and Molecular Physics, and Optics, Formalism (philosophy of mathematics), Xenon, chemistry, Quantum electrodynamics, Caesium, Atomic physics, Unified field theory, Anisotropy, media_common
Abstract: A unified theory of collisional line profiles has been applied to the case of the D1 and D2 lines of caesium perturbed by xenon for which experiments are available. A Lennard-Jones potential has been used and interaction anisotropy has been included. It is shown that Hund's c case is valid, which allows us to simplify the formalism. For intermediate pressures the computed profiles show multiple satellites whose reality is corroborated by an experimental filtered profile. The asymmetry parameter is shown to be a good choice to use for testing interatomic potentials.
Published: 1974
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36. Collision-broadened spectral line profiles in the limit of high perturber density

Author: N. F. Allard, A. Chevillot, and Y. G. Biraud
Subjects: Physics, symbols.namesake, Fourier transform, Mathematical model, Fourier analysis, Autocorrelation, symbols, Limit (mathematics), Atomic physics, Collision, Spectral line, Line (formation)
Abstract: In the present research we have used a Fourier spectral analysis to study line profiles due to strong atom-atom interactions in the limit of high perturber density. The presence of multiple satellites in this case is well explained. Moreover, for decreasing interactions and densities we may extrapolate our results and explain the disappearance of the satellites. The use of ``a crude potential shape''\char22{}here a square-well\char22{}proves to be sufficient to explain the presence of multiple satellites and determine the necessary physical conditions for their appearance.
Published: 1988

37. Analysis of Helium-rich White Dwarfs Polluted by Heavy Elements in the Gaia Era.

Author: S. Coutu, P. Dufour, P. Bergeron, S. Blouin, E. Loranger, N. F. Allard, and B. H. Dunlap
Subjects: HEAVY elements, WHITE dwarf stars, SUPERGIANT stars, PARALLAX, ASTRONOMICAL surveys, ATMOSPHERIC models
Abstract: We present an analysis of 1023 DBZ/DZ(A) and 319 DQ white dwarf stars taken from the Montreal White Dwarf Database. This represents a significant increase over the previous comprehensive studies on these types of objects. We use new trigonometric parallax measurements from the Gaia second data release, together with photometry from the Sloan Digital Sky Survey, Pan-STARRS, Gaia, or BVRI from the literature, which allow the determination of the mass for the majority of the objects in our sample. We use the photometric and spectroscopic techniques with our recently improved model atmospheres code, which include high-density effects, to accurately determine the effective temperature, surface gravity, and heavy-element abundances for each object. We study the abundance of hydrogen in DBZ/DZ white dwarfs and the properties of the accreted planetesimals. We explore the nature of the second sequence of DQ stars using proper motions from Gaia and highlight evidence of crystallization in massive DQ stars. We also present mass distributions for both spectral types. Finally, we discuss the implications of our findings in the context of the spectral evolution of white dwarfs and provide the atmospheric parameters for each star. [ABSTRACT FROM AUTHOR]
Published: 2019
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38. A New Generation of Cool White Dwarf Atmosphere Models. IV. Revisiting the Spectral Evolution of Cool White Dwarfs.

Author: S. Blouin, P. Dufour, C. Thibeault, and N. F. Allard
Subjects: WHITE dwarf stars, ATMOSPHERIC models, ATMOSPHERIC composition, BIOLOGICAL evolution, INTERSTELLAR medium, PARALLAX
Abstract: As a result of competing physical mechanisms, the atmospheric composition of white dwarfs changes throughout their evolution, a process known as spectral evolution. Because of the ambiguity of their atmospheric compositions and the difficulties inherent to the modeling of their dense atmospheres, no consensus exists regarding the spectral evolution of cool white dwarfs (Teff < 6000 K). In the previous papers of this series, we presented and observationally validated a new generation of cool white dwarf atmosphere models that include all the necessary constitutive physics to accurately model those objects. Using these new models and a homogeneous sample of 501 cool white dwarfs, we revisit the spectral evolution of cool white dwarfs. Our sample includes all spectroscopically identified white dwarfs cooler than 8300 K for which a parallax is available in Gaia DR2 and photometric observations are available in Pan-STARRS1 and 2MASS. Except for a few cool carbon-polluted objects, our models allow an excellent fit to the spectroscopic and photometric observations of all objects included in our sample. We identify a decrease of the ratio of hydrogen- to helium-rich objects between 7500 and 6250 K, which we interpret as the signature of convective mixing. After this decrease, hydrogen-rich objects become more abundant up to 5000 K. This puzzling increase, reminiscent of the non-DA gap, has yet to be explained. At lower temperatures, below 5000 K, hydrogen-rich white dwarfs become rarer, which rules out the scenario in which the accretion of hydrogen from the interstellar medium dominates the spectral evolution of cool white dwarfs. [ABSTRACT FROM AUTHOR]
Published: 2019
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39. Line Profiles of the Calcium I Resonance Line in Cool Metal-polluted White Dwarfs.

Author: S. Blouin, N. F. Allard, T. Leininger, F. X. Gadéa, and P. Dufour
Subjects: *WHITE dwarf stars, *ATMOSPHERIC models, *RESONANCE, *SPECTRAL lines, *HEAVY elements, *MOLECULAR magnetic moments
Abstract: Metal-polluted white dwarfs (DZ stars) are characterized by a helium-rich atmosphere contaminated by heavy elements traces originating from accreted rocky planetesimals. As a detailed spectroscopic analysis of those objects can reveal the composition of the accreted debris, there is a great interest in developing accurate DZ atmosphere models. However, the coolest DZ white dwarfs are challenging to model due to the fluidlike density of their atmospheres. Under such extreme conditions, spectral absorption lines are heavily broadened by interactions with neutral helium, and it is no longer justified to use the conventional Lorentzian profiles. In this work, we determine the theoretical profiles of the Ca i resonance line (the most prominent spectral line for the coolest DZ white dwarfs) in the dense atmospheres of cool DZ white dwarfs. To do so, we use a unified theory of collisional line profiles and accurate ab initio potential energies and transition dipole moments for the CaHe molecule. We present the resulting profiles for the full range of temperatures and helium densities relevant for the modeling of cool, metal-polluted white dwarfs (from 3000 to 6000 K and from 1021 to 1023 cm−3). We also implement these new profiles in our atmosphere models and show that they lead to improved fits to the Ca i resonance line of the coolest DZ white dwarfs. [ABSTRACT FROM AUTHOR]
Published: 2019
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40. A New Generation of Cool White Dwarf Atmosphere Models. III. WD J2356–209: Accretion of a Planetesimal with an Unusual Composition.

Author: S. Blouin, P. Dufour, N. F. Allard, S. Salim, R. M. Rich, and L. V. E. Koopmans
Subjects: WHITE dwarf stars, STELLAR atmospheres, ACCRETION (Astrophysics), PLANETESIMALS, STELLAR spectra, ASTRONOMICAL photometry
Abstract: WD J2356−209 is a cool metal-polluted white dwarf whose visible spectrum is dominated by a strong and broad sodium feature. Although it was discovered nearly two decades ago, no detailed and realistic analysis of this star had yet been realized. In the absence of atmosphere models taking into account the nonideal high-density effects arising at the photosphere of WD J2356−209, the origin of its unique spectrum had remained nebulous. We use the cool white dwarf atmosphere code presented in the first paper of this series to finally reveal the secrets of this peculiar object and details about the planetesimal that polluted its atmosphere. Thanks to the improved input physics of our models, we find a solution that is in excellent agreement with the photometric observations and the visible spectrum. Our solution reveals that the photosphere of WD J2356−209 has a number density ratio of , which is the highest ever found in a white dwarf. Since we do not know how long ago the accretion episode stopped (if it has), we cannot precisely determine the composition nor the mass of the accreted planetesimal. Nevertheless, all scenarios considered indicate that its composition is incompatible with that of chondrite-like material and that its mass was at least 1021 g. [ABSTRACT FROM AUTHOR]
Published: 2019
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41. A New Generation of Cool White Dwarf Atmosphere Models. II. A DZ Star with Collision-induced Absorption.

Author: S. Blouin, P. Dufour, N. F. Allard, and M. Kilic
Subjects: WHITE dwarf stars, DWARF stars, NOVAE (Astronomy), MAGELLANIC clouds, DWARF galaxies
Abstract: In the first paper of this series, we presented our upgraded cool white dwarf atmosphere code. In this second paper, we use our new models to analyze SDSS J080440.63+223948.6 (J0804+2239), the first DZ star to show collision-induced absorption (CIA). This object provides a crucial test for our models, since previous versions of our code were unable to simultaneously fit the metal absorption lines and the CIA. We find an excellent fit to both the spectroscopic and photometric data, which further validates the improved constitutive physics of our models. We also show that the presence of metal lines allows lift of the degeneracy between high and low hydrogen abundances that usually affects the fits of white dwarfs with CIA. Finally, we investigate the potential impact of spectroscopically undetected metals on the photometric solutions of DC stars. [ABSTRACT FROM AUTHOR]
Published: 2018
Full Text: View/download PDF

42. A New Generation of Cool White Dwarf Atmosphere Models. I. Theoretical Framework and Applications to DZ Stars.

Author: S. Blouin, P. Dufour, and N. F. Allard
Subjects: WHITE dwarf stars, ATMOSPHERIC models, HELIUM, HEAVY elements, SPECTRAL energy distribution
Abstract: The photospheres of the coolest helium-atmosphere white dwarfs are characterized by fluidlike densities. Under those conditions, standard approximations used in model atmosphere codes are no longer appropriate. Unfortunately, the majority of cool He-rich white dwarfs show no spectral features, giving us no opportunities to put more elaborate models to the test. In the few cases where spectral features are observed (such as in cool DQ or DZ stars), current models completely fail to reproduce the spectroscopic data, signaling shortcomings in our theoretical framework. In order to fully trust parameters derived solely from the energy distribution, it is thus important to at least succeed in reproducing the spectra of the few coolest stars exhibiting spectral features, especially since such stars possess even less extreme physical conditions due to the presence of heavy elements. In this paper, we revise every building block of our model atmosphere code in order to eliminate low-density approximations. Our updated white dwarf atmosphere code incorporates state-of-the-art constitutive physics suitable for the conditions found in cool helium-rich stars (DC and DZ white dwarfs). This includes new high-density metal-line profiles, nonideal continuum opacities, an accurate equation of state, and a detailed description of the ionization equilibrium. In particular, we present new ab initio calculations to assess the ionization equilibrium of heavy elements (C, Ca, Fe, Mg, and Na) in a dense helium medium and show how our improved models allow us to achieve better spectral fits for two cool DZ stars, Ross 640 and LP 658-2. [ABSTRACT FROM AUTHOR]
Published: 2018
Full Text: View/download PDF

43. Blue line wings of resonance lines of potassium and sodium perturbed by molecular hydrogen and rare gases.

Author: J F Kielkopf, N F Allard, V A Alekseev, F Spiegelman, G Guillon, and H Berriche
Published: 2017
Full Text: View/download PDF

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