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14 pages, 333 KiB

Open AccessFeature PaperArticle

Quantum and Semiclassical Stark Widths for Ar VII Spectral Lines

by Rihab Aloui, Haykel Elabidi, Sylvie Sahal-Bréchot and Milan S. Dimitrijević

Atoms 2018, 6(2), 20; https://doi.org/10.3390/atoms6020020 - 16 Apr 2018

Cited by 15 | Viewed by 3085

Abstract

We present in this paper the results of a theoretical study of electron impact broadening for several lines of the Ar VII ion. The results have been obtained using our quantum mechanical method and the semiclassical perturbation one. Results are presented for electron [...] Read more.

We present in this paper the results of a theoretical study of electron impact broadening for several lines of the Ar VII ion. The results have been obtained using our quantum mechanical method and the semiclassical perturbation one. Results are presented for electron density 10¹⁸ cm⁻³ and for electron temperatures ranging from

2 \times 10^{4}

to

5 \times 10^{5}

K required for plasma modeling. Our results have been compared to other semiclassical ones obtained using different sources of atomic data. A study of the strong collisions contributions to line broadening has been performed. The atomic structure and collision data used for the calculations of line broadening are also calculated by our codes and compared to available theoretical results. The agreement found between the two calculations ensures that our line broadening procedure uses adequate structure and collision data. Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

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7 pages, 1266 KiB

Open AccessArticle

Doppler Broadening of Spectral Line Shapes in Relativistic Plasmas

by Mohammed Tayeb Meftah, Hadda Gossa, Kamel Ahmed Touati, Keltoum Chenini and Amel Naam

Atoms 2018, 6(2), 16; https://doi.org/10.3390/atoms6020016 - 4 Apr 2018

Cited by 3 | Viewed by 4881

Abstract

In this work, we report some relativistic effects on the spectral line broadening. In particular, we give a new Doppler broadening in extra hot plasmas that takes into account the possible high velocity of the emitters. This suggests the use of an appropriate [...] Read more.

In this work, we report some relativistic effects on the spectral line broadening. In particular, we give a new Doppler broadening in extra hot plasmas that takes into account the possible high velocity of the emitters. This suggests the use of an appropriate distribution of the velocities for the emitters. Indeed, the Juttner-Maxwell distribution of the velocities is more adequate for relativistic velocities of the emitters when the latter are in plasma with an extra high temperature. We find an asymmetry in the Doppler line shapes unlike the case of the traditional Doppler effect. Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

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7 pages, 750 KiB

Open AccessFeature PaperArticle

Stark Broadening of Se IV, Sn IV, Sb IV and Te IV Spectral Lines

by Milan S. Dimitrijević, Zoran Simić, Roland Stamm, Joël Rosato, Nenad Milovanović and Cristina Yubero

Atoms 2018, 6(1), 10; https://doi.org/10.3390/atoms6010010 - 7 Mar 2018

Cited by 8 | Viewed by 3347

Abstract

Stark broadening parameters, line width and shift, are needed for investigations, analysis and modelling of astrophysical, laboratory, laser produced and technological plasmas. Especially in astrophysics, due to constantly increasing resolution of satellite borne spectrographs, and large terrestrial telescopes, data on trace elements, which [...] Read more.

Stark broadening parameters, line width and shift, are needed for investigations, analysis and modelling of astrophysical, laboratory, laser produced and technological plasmas. Especially in astrophysics, due to constantly increasing resolution of satellite borne spectrographs, and large terrestrial telescopes, data on trace elements, which were previously insignificant, now have increasing importance. Using the modified semiempirical method of Dimitrijević and Konjević, here, Stark widths have been calculated for 2 Se IV, 6 Sn IV, 2 Sb IV and 1 Te IV transitions. Results have been compared with existing theoretical data for Sn IV. Obtained results will be implemented in the STARK-B database, which is also a part of Virtual atomic and molecular data center (VAMDC). Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

6 pages, 272 KiB

Open AccessArticle

Contribution of Lienard-Wiechert Potential to the Electron Broadening of Spectral Lines in Plasmas

by Mohammed Tayeb Meftah, Khadra Arif, Keltoum Chenini, Kamel Ahmed Touati and Said Douis

Atoms 2018, 6(1), 6; https://doi.org/10.3390/atoms6010006 - 8 Feb 2018

Cited by 1 | Viewed by 3354

Abstract

Lienard-Wiechert or retarded electric and magnetic fields are produced by moving electric charges with respect to a rest frame. In hot plasmas, such fields may be created by high velocity free electrons. The resulting electric field has a relativistic expression that depends on [...] Read more.

Lienard-Wiechert or retarded electric and magnetic fields are produced by moving electric charges with respect to a rest frame. In hot plasmas, such fields may be created by high velocity free electrons. The resulting electric field has a relativistic expression that depends on the ratio of the free electron velocity to the speed of light in vacuum c. In this work, we consider the semi-classical dipole interaction between the emitter ions and the Lienard-Wiechert electric field of the free electrons and compute its contribution to the broadening of the spectral line shape in hot and dense plasmas. Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

8 pages, 280 KiB

Open AccessFeature PaperArticle

The Application of the Cut-Off Coulomb Model Potential for the Calculation of Bound-Bound State Transitions

by Nenad M. Sakan, Vladimir A. Srećković, Zoran J. Simić and Milan S. Dimitrijević

Atoms 2018, 6(1), 4; https://doi.org/10.3390/atoms6010004 - 12 Jan 2018

Cited by 1 | Viewed by 3441

Abstract

In this contribution, we present results of bound state transition modeling using the cut-off Coulomb model potential. The cut-off Coulomb potential has proven itself as a model potential for the dense hydrogen plasma. The main aim of our investigation include further steps of [...] Read more.

In this contribution, we present results of bound state transition modeling using the cut-off Coulomb model potential. The cut-off Coulomb potential has proven itself as a model potential for the dense hydrogen plasma. The main aim of our investigation include further steps of improvement of the usage of model potential. The results deal with partially ionized dense hydrogen plasma. The presented results covers

N_{e} = 6.5 \times 10^{18} {cm}^{- 3}

,

T = 18,000 K

and

N_{e} = 1.5 \times 10^{19} {cm}^{- 3}

,

T = 23,000 K,

where the comparison with the experimental data should take place, and the theoretical values for comparison. Since the model was successfully applied on continuous photoabsorption of dense hydrogen plasma in the broad area of temperatures and densities, it is expected to combine both continuous and bound-bound photoabsorption within single quantum mechanical model with the same success. Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

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877 KiB

Open AccessFeature PaperArticle

Nonlinear Spectroscopy of Alkali Atoms in Cold Medium of Astrophysical Relevance

by Dmitry K. Efimov, Martins Bruvelis, Nikolai N. Bezuglov, Milan S. Dimitrijević, Andrey N. Klyucharev, Vladimir A. Srećković, Yurij N. Gnedin and Francesco Fuso

Atoms 2017, 5(4), 50; https://doi.org/10.3390/atoms5040050 - 6 Dec 2017

Cited by 9 | Viewed by 4046

Abstract

The time-dependent population dynamics of hyperfine (HF) sublevels of

n^{2} p_{3 / 2}

atomic states upon laser excitation in a cold medium of alkali atoms is examined. We demonstrate some peculiarities of the absorption HF multiplet formation in D2-line resulting [...] Read more.

The time-dependent population dynamics of hyperfine (HF) sublevels of

n^{2} p_{3 / 2}

atomic states upon laser excitation in a cold medium of alkali atoms is examined. We demonstrate some peculiarities of the absorption HF multiplet formation in D2-line resulting from a long interaction time (∼200

μ

s) interaction between light and Na (

n = 3

) and Cs (

n = 6

) atoms in a cold and slow sub-thermal (

T \sim 1

K) beam. We analytically describe a number of D2-line-shape effects that are of interest in spectroscopic studies of cold dusty white dwarfs: broadening by optical pumping, intensity redistribution within components of D2-line HF multiplet for partially closed transitions and asymmetry of absorption lines induced by AC Stark shifts for cyclic transitions. Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

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220 KiB

Open AccessFeature PaperArticle

Regularities and Systematic Trends on Zr IV Stark Widths

by Zlatko Majlinger, Milan S. Dimitrijević and Zoran Simić

Atoms 2017, 5(4), 49; https://doi.org/10.3390/atoms5040049 - 1 Dec 2017

Cited by 3 | Viewed by 2772

Abstract

Regularities and systematic trends among the Stark widths of 18 Zr IV spectral lines obtained by modified semiempirical approach have been discussed. Also we compared those calculated Stark broadening parameters with estimates according to Cowley, Purić et al. and Purić and Šćepanović and [...] Read more.

Regularities and systematic trends among the Stark widths of 18 Zr IV spectral lines obtained by modified semiempirical approach have been discussed. Also we compared those calculated Stark broadening parameters with estimates according to Cowley, Purić et al. and Purić and Šćepanović and checked the possibility to find some new estimates. It is demonstrated as well that the formula of Cowley (1971) overestimates Stark widths, obtained by using modified semiempirical method, with the increase of angular orbital momentum quantum number due to its neglection. It is also found that the results obtained by using formula for simple estimates of Purić et al. (1991) are in agreement with the modified semiempirical results within the estimated error bars of both methods, while the estimates using formula of Purić and Šćepanović (1999) are in strong disagreement which increases with the increase of angular orbital momentum quantum number. Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

5446 KiB

Open AccessFeature PaperArticle

Rosetta Mission: Electron Scattering Cross Sections—Data Needs and Coverage in BEAMDB Database

by Bratislav P. Marinković, Jan Hendrik Bredehöft, Veljko Vujčić, Darko Jevremović and Nigel J. Mason

Atoms 2017, 5(4), 46; https://doi.org/10.3390/atoms5040046 - 17 Nov 2017

Cited by 10 | Viewed by 4771

Abstract

The emission of [O I] lines in the coma of Comet 67P/Churyumov-Gerasimenko during the Rosetta mission have been explained by electron impact dissociation of water rather than the process of photodissociation. This is the direct evidence for the role of electron induced processing [...] Read more.

The emission of [O I] lines in the coma of Comet 67P/Churyumov-Gerasimenko during the Rosetta mission have been explained by electron impact dissociation of water rather than the process of photodissociation. This is the direct evidence for the role of electron induced processing has been seen on such a body. Analysis of other emission features is handicapped by a lack of detailed knowledge of electron impact cross sections which highlights the need for a broad range of electron scattering data from the molecular systems detected on the comet. In this paper, we present an overview of the needs for electron scattering data relevant for the understanding of observations in coma, the tenuous atmosphere and on the surface of 67P/Churyumov-Gerasimenko during the Rosetta mission. The relevant observations for elucidating the role of electrons come from optical spectra, particle analysis using the ion and electron sensors and mass spectrometry measurements. To model these processes electron impact data should be collated and reviewed in an electron scattering database and an example is given in the BEAMD, which is a part of a larger consortium of Virtual Atomic and Molecular Data Centre—VAMDC. Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

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2388 KiB

Open AccessFeature PaperArticle

Active Galactic Nuclei Search

by Sergey Kotov and Sergey Dodonov

Atoms 2017, 5(4), 45; https://doi.org/10.3390/atoms5040045 - 10 Nov 2017

Cited by 1 | Viewed by 3587

Abstract

We present the first results of medium-band photometric observations on the 1m Schmidt Telescope of Byurakan Astrophysical Observatory (Armenia). The object sample was created in the SA68 field. The medium-band filter set (13 filters with FWHM = 250 Å + 5 broadband SDSS [...] Read more.

We present the first results of medium-band photometric observations on the 1m Schmidt Telescope of Byurakan Astrophysical Observatory (Armenia). The object sample was created in the SA68 field. The medium-band filter set (13 filters with FWHM = 250 Å + 5 broadband SDSS filters) allowed us to create low-resolution spectra of each object in the SA68 field. We compared them with the template spectra to select AGNs and to determine their photometric redshifts. Our sample consists of 330 objects with 0.5–5.1 redshift range and complete up to 23.0 AB magnitude. The comparison of our sample with SDSS DR10 and BOSS + MMT QSO showed that sufficiently more objects in the 3.2–5.1 redshift range were found. Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

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917 KiB

Open AccessFeature PaperArticle

A New Analysis of Stark and Zeeman Effects on Hydrogen Lines in Magnetized DA White Dwarfs

by Ny Kieu, Joël Rosato, Roland Stamm, Jelena Kovačević-Dojcinović, Milan S. Dimitrijević, Luka Č. Popović and Zoran Simić

Atoms 2017, 5(4), 44; https://doi.org/10.3390/atoms5040044 - 6 Nov 2017

Cited by 15 | Viewed by 4845

Abstract

White dwarfs with magnetic field strengths larger than 10 T are understood to represent more than 10% of the total population of white dwarfs. The presence of such strong magnetic fields is clearly indicated by the Zeeman triplet structure visible on absorption lines. [...] Read more.

White dwarfs with magnetic field strengths larger than 10 T are understood to represent more than 10% of the total population of white dwarfs. The presence of such strong magnetic fields is clearly indicated by the Zeeman triplet structure visible on absorption lines. In this work, we discuss the line broadening mechanisms and focus on the sensitivity of hydrogen lines on the magnetic field. We perform new calculations in conditions relevant to magnetized DA stellar atmospheres using models inspired from magnetic fusion plasma spectroscopy. A white dwarf spectrum from the Sloan Digital Sky Survey (SDSS) database is analyzed. An effective temperature is provided by an adjustment of the background radiation with a Planck function, and the magnetic field is inferred from absorption lines presenting a Zeeman triplet structure. An order-of-magnitude estimate for the electron density is also performed from Stark broadening analysis. Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

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567 KiB

Open AccessFeature PaperArticle

Models of Emission-Line Profiles and Spectral Energy Distributions to Characterize the Multi-Frequency Properties of Active Galactic Nuclei

by Giovanni La Mura, Marco Berton, Sina Chen, Abhishek Chougule, Stefano Ciroi, Enrico Congiu, Valentina Cracco, Michele Frezzato, Sabrina Mordini and Piero Rafanelli

Atoms 2017, 5(4), 43; https://doi.org/10.3390/atoms5040043 - 6 Nov 2017

Cited by 1 | Viewed by 4357

Abstract

The spectra of active galactic nuclei (AGNs) are often characterized by a wealth of emission lines with different profiles and intensity ratios that lead to a complicated classification. Their electromagnetic radiation spans more than 10 orders of magnitude in frequency. In spite of [...] Read more.

The spectra of active galactic nuclei (AGNs) are often characterized by a wealth of emission lines with different profiles and intensity ratios that lead to a complicated classification. Their electromagnetic radiation spans more than 10 orders of magnitude in frequency. In spite of the differences between various classes, the origin of their activity is attributed to a combination of emitting components, surrounding an accreting supermassive black hole (SMBH), in the unified model. Currently, the execution of sky surveys, with instruments operating at various frequencies, provides the possibility to detect and to investigate the properties of AGNs on very large statistical samples. As a result of the spectroscopic surveys that allow the investigation of many objects, we have the opportunity to place new constraints on the nature and evolution of AGNs. In this contribution, we present the results obtained by working on multi-frequency data, and we discuss their relations with the available optical spectra. We compare our findings with the AGN unified model predictions, and we present a revised technique to select AGNs of different types from other line-emitting objects. We discuss the multi-frequency properties in terms of the innermost structures of the sources. Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

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493 KiB

Open AccessFeature PaperArticle

The Screening Characteristics of the Dense Astrophysical Plasmas: The Three-Component Systems

by Ljubinko M. Ignjatović, Vladimir A. Srećković and Milan S. Dimitrijević

Atoms 2017, 5(4), 42; https://doi.org/10.3390/atoms5040042 - 2 Nov 2017

Cited by 4 | Viewed by 3397

Abstract

As the object of investigation, astrophysical fully ionized electron-ion plasma is chosen with positively charged ions of two different kinds, including the plasmas of higher non-ideality. The direct aim of this work is to develop, within the problem of finding the mean potential [...] Read more.

As the object of investigation, astrophysical fully ionized electron-ion plasma is chosen with positively charged ions of two different kinds, including the plasmas of higher non-ideality. The direct aim of this work is to develop, within the problem of finding the mean potential energy of the charged particle for such plasma, a new model, self-consistent method of describing the electrostatic screening. Within the presented method, such extremely significant phenomena as the electron-ion and ion-ion correlations are included in the used model. We wish to draw attention to the fact that the developed method is suitable for astrophysical applications. Here we keep in mind that in outer shells of stars, the physical conditions change from those that correspond to the rare, practically ideal plasma, to those that correspond to extremely dense non-ideal plasma. Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

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1035 KiB

Open AccessFeature PaperArticle

Using the Pairs of Lines Broadened by Collisions with Neutral and Charged Particles for Gas Temperature Determination of Argon Non-Thermal Plasmas at Atmospheric Pressure

by Cristina Yubero, Antonio Rodero, Milan S. Dimitrijevic, Antonio Gamero and Maria Del Carmen García

Atoms 2017, 5(4), 41; https://doi.org/10.3390/atoms5040041 - 23 Oct 2017

Cited by 4 | Viewed by 3993

Abstract

The spectroscopic method for gas temperature determination in argon non-thermal plasmas sustained at atmospheric pressure proposed recently by Spectrochimica Acta Part B 129 14 (2017)—based on collisional broadening measurements of selected pairs of argon atomic lines, has been applied to other pairs of [...] Read more.

The spectroscopic method for gas temperature determination in argon non-thermal plasmas sustained at atmospheric pressure proposed recently by Spectrochimica Acta Part B 129 14 (2017)—based on collisional broadening measurements of selected pairs of argon atomic lines, has been applied to other pairs of argon atomic lines, and the discrepancies found in some of these results have been analyzed. For validation purposes, the values of the gas temperature obtained using the different pairs of lines have been compared with the rotational temperatures derived from the OH ro-vibrational bands, using the Boltzmann-plot technique. Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

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4023 KiB

Open AccessFeature PaperArticle

Detailed Investigation of the Electric Discharge Plasma between Copper Electrodes Immersed into Water

by Roman Venger, Tetiana Tmenova, Flavien Valensi, Anatoly Veklich, Yann Cressault and Viacheslav Boretskij

Atoms 2017, 5(4), 40; https://doi.org/10.3390/atoms5040040 - 23 Oct 2017

Cited by 17 | Viewed by 4308

Abstract

A phenomenological picture of pulsed electrical discharge in water is produced by combining electrical, spectroscopic, and imaging methods. The discharge is generated by applying ~350 μs long 100 to 220 V pulses (values of current from 400 to 1000 A, respectively) between the [...] Read more.

A phenomenological picture of pulsed electrical discharge in water is produced by combining electrical, spectroscopic, and imaging methods. The discharge is generated by applying ~350 μs long 100 to 220 V pulses (values of current from 400 to 1000 A, respectively) between the point-to-point copper electrodes submerged into the non-purified tap water. Plasma channel and gas bubble occur between the tips of the electrodes, which are initially in contact with each other. The study includes detailed experimental investigation of plasma parameters of such discharge using the correlation between time-resolved high-speed imaging, electrical characteristics, and optical emission spectroscopic data. Radial distributions of the electron density of plasma is estimated from the analysis of profiles and widths of registered H_α and H_β hydrogen lines, and Cu I 515.3 nm line, exposed to the Stark mechanism of spectral lines’ broadening. Estimations of the electrodes’ erosion rate and bubbles’ size depending on the electrical input parameters of the circuit are presented. Experimental results of this work may be valuable for the advancement of modeling and the theoretical understanding of the pulse electric discharges in water. Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

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2320 KiB

Open AccessFeature PaperArticle

Stark-Zeeman Line Shape Modeling for Magnetic White Dwarf and Tokamak Edge Plasmas: Common Challenges

by Joël Rosato, Ny Kieu, Ibtissem Hannachi, Mohammed Koubiti, Yannick Marandet, Roland Stamm, Milan S. Dimitrijević and Zoran Simić

Atoms 2017, 5(4), 36; https://doi.org/10.3390/atoms5040036 - 4 Oct 2017

Cited by 7 | Viewed by 4292

Abstract

The shape of atomic spectral lines in plasmas contains information on the plasma parameters, and can be used as a diagnostic tool. Under specific conditions, the plasma located at the edge of tokamaks has parameters similar to those in magnetic white dwarf stellar [...] Read more.

The shape of atomic spectral lines in plasmas contains information on the plasma parameters, and can be used as a diagnostic tool. Under specific conditions, the plasma located at the edge of tokamaks has parameters similar to those in magnetic white dwarf stellar atmospheres, which suggests that the same line shape models can be used. A problem common to tokamak and magnetic white dwarfs concerns the modeling of Stark broadening of hydrogen lines in the presence of an external magnetic field and the related Zeeman effect. In this work, we focus on a selection of issues relevant to Stark broadening in magnetized hydrogen plasmas. Various line shape models are presented and discussed through applications to ideal cases. Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

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456 KiB

Open AccessFeature PaperArticle

Line Shape Modeling for the Diagnostic of the Electron Density in a Corona Discharge

by Joël Rosato, Nelly Bonifaci, Zhiling Li and Roland Stamm

Atoms 2017, 5(4), 35; https://doi.org/10.3390/atoms5040035 - 28 Sep 2017

Cited by 4 | Viewed by 3659

Abstract

We present an analysis of spectra observed in a corona discharge designed for the study of dielectrics in electrical engineering. The medium is a gas of helium and the discharge was performed at the vicinity of a tip electrode under high voltage. The [...] Read more.

We present an analysis of spectra observed in a corona discharge designed for the study of dielectrics in electrical engineering. The medium is a gas of helium and the discharge was performed at the vicinity of a tip electrode under high voltage. The shape of helium lines is dominated by the Stark broadening due to the plasma microfield. Using a computer simulation method, we examine the sensitivity of the He 492 nm line shape to the electron density. Our results indicate the possibility of a density diagnostic based on passive spectroscopy. The influence of collisional broadening due to interactions between the emitters and neutrals is discussed. Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

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8034 KiB

Open AccessFeature PaperArticle

Effect of Turbulence on Line Shapes in Astrophysical and Fusion Plasmas

by Ibtissem Hannachi, Mutia Meireni, Paul Génésio, Joël Rosato, Roland Stamm and Yannick Marandet

Atoms 2017, 5(4), 34; https://doi.org/10.3390/atoms5040034 - 25 Sep 2017

Viewed by 3850

Abstract

We look at the effect of wave collapse turbulence on a hydrogen line shape in plasma. An atom immersed in plasma affected by strong Langmuir turbulence may be perturbed by a sequence of wave packets with a maximum electric field magnitude that is [...] Read more.

We look at the effect of wave collapse turbulence on a hydrogen line shape in plasma. An atom immersed in plasma affected by strong Langmuir turbulence may be perturbed by a sequence of wave packets with a maximum electric field magnitude that is larger than the Holtsmark field. For such conditions, we propose to calculate the shape of the hydrogen Lyman α Lyman β and Balmer α lines with a numerical integration of the Schrödinger equation coupled to a simulation of a sequence of electric fields modeling the effects of the Langmuir wave. We present and discuss several line profiles of Lyman and Balmer lines. Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

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1210 KiB

Open AccessFeature PaperArticle

Quasar Black Hole Mass Estimates from High-Ionization Lines: Breaking a Taboo?

by Paola Marziani, Ascensión Del Olmo, Mary Loli Martínez-Aldama, Deborah Dultzin, Alenka Negrete, Edi Bon, Natasa Bon and Mauro D’Onofrio

Atoms 2017, 5(3), 33; https://doi.org/10.3390/atoms5030033 - 20 Sep 2017

Cited by 9 | Viewed by 4457

Abstract

Can high ionization lines such as CIV

λ

1549 provide useful virial broadening estimators for computing the mass of the supermassive black holes that power the quasar phenomenon? The question has been dismissed by several workers as a rhetorical one because blue-shifted, non-virial [...] Read more.

Can high ionization lines such as CIV

λ

1549 provide useful virial broadening estimators for computing the mass of the supermassive black holes that power the quasar phenomenon? The question has been dismissed by several workers as a rhetorical one because blue-shifted, non-virial emission associated with gas outflows is often prominent in CIV

λ

1549 line profiles. In this contribution, we first summarize the evidence suggesting that the FWHM of low-ionization lines like H

β

and MgII

λ

2800 provide reliable virial broadening estimators over a broad range of luminosity. We confirm that the line widths of CIV

λ

1549 is not immediately offering a virial broadening estimator equivalent to the width of low-ionization lines. However, capitalizing on the results of Coatman et al. (2016) and Sulentic et al. (2017), we suggest a correction to FWHM CIV

λ

1549 for Eddington ratio and luminosity effects that, however, remains cumbersome to apply in practice. Intermediate ionization lines (IP ∼ 20–30 eV; AlIII

λ

1860 and SiIII]

λ

1892) may provide a better virial broadening estimator for high redshift quasars, but larger samples are needed to assess their reliability. Ultimately, they may be associated with the broad-line region radius estimated from the photoionization method introduced by Negrete et al. (2013) to obtain black hole mass estimates independent from scaling laws. Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

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2918 KiB

Open AccessFeature PaperArticle

Stark Broadening from Impact Theory to Simulations

by Roland Stamm, Ibtissem Hannachi, Mutia Meireni, Laurence Godbert-Mouret, Mohammed Koubiti, Yannick Marandet, Joël Rosato, Milan S. Dimitrijević and Zoran Simić

Atoms 2017, 5(3), 32; https://doi.org/10.3390/atoms5030032 - 20 Sep 2017

Cited by 3 | Viewed by 3780

Abstract

Impact approximation is widely used for calculating Stark broadening in a plasma. We review its main features and different types of models that make use of it. We discuss recent developments, in particular a quantum approach used for both the emitter and the [...] Read more.

Impact approximation is widely used for calculating Stark broadening in a plasma. We review its main features and different types of models that make use of it. We discuss recent developments, in particular a quantum approach used for both the emitter and the perturbers. Numerical simulations are a useful tool for gaining insight into the mechanisms at play in impact-broadening conditions. Our simple model allows the integration of the Schrödinger equation for an emitter submitted to a fluctuating electric field. We show how we can approach the impact results, and how we can investigate conditions beyond the impact approximation. The simple concepts developed in impact and simulation approaches enable the analysis of complex problems such as the effect of plasma rogue waves on hydrogen spectra. Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

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597 KiB

Open AccessFeature PaperArticle

Radiative and Collisional Molecular Data and Virtual Laboratory Astrophysics

by Vladimir A. Srećković, Ljubinko M. Ignjatović, Darko Jevremović, Veljko Vujčić and Milan S. Dimitrijević

Atoms 2017, 5(3), 31; https://doi.org/10.3390/atoms5030031 - 19 Sep 2017

Cited by 17 | Viewed by 3507

Abstract

Spectroscopy has been crucial for our understanding of physical and chemical phenomena. The interpretation of interstellar line spectra with radiative transfer calculations usually requires two kinds of molecular input data: spectroscopic data (such as energy levels, statistical weights, transition probabilities, etc.) and collision [...] Read more.

Spectroscopy has been crucial for our understanding of physical and chemical phenomena. The interpretation of interstellar line spectra with radiative transfer calculations usually requires two kinds of molecular input data: spectroscopic data (such as energy levels, statistical weights, transition probabilities, etc.) and collision data. This contribution describes how such data are collected, stored, and which limitations exist. Also, here we summarize challenges of atomic/molecular databases and point out our experiences, problems, etc., which we are faced with. We present overview of future developments and needs in the areas of radiative transfer and molecular data. Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

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733 KiB

Open AccessFeature PaperArticle

Stark Widths of Na IV Spectral Lines

by Milan S. Dimitrijević, Zoran Simić, Aleksandar Valjarević and Cristina Yubero

Atoms 2017, 5(3), 29; https://doi.org/10.3390/atoms5030029 - 18 Sep 2017

Viewed by 3438

Abstract

Sodium is a very important element for the research and analysis of astrophysical, laboratory, and technological plasmas, but neither theoretical nor experimental data on Stark broadening of Na IV spectral lines are present in the literature. Using the modified semiempirical method of Dimitrijević [...] Read more.

Sodium is a very important element for the research and analysis of astrophysical, laboratory, and technological plasmas, but neither theoretical nor experimental data on Stark broadening of Na IV spectral lines are present in the literature. Using the modified semiempirical method of Dimitrijević and Konjević, here Stark widths have been calculated for nine Na IV transitions. Na IV belongs to the oxygen isoelectronic sequence, and we have calculated Stark widths belonging to singlets, triplets, and quintuplets, as well as with different parent terms. This is used to discuss similarities within one transition array with different multiplicities and parent terms. Additionally, calculated widths will be implemented in the STARK-B database (http://stark-b.obspm.fr) which is also a part of the Virtual Atomic and Molecular Data Center (VAMDC—http://www.vamdc.org/). Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

228 KiB

Open AccessFeature PaperArticle

Semiclassical Stark Broadening Parameters of Ar VII Spectral Lines

by Milan S. Dimitrijević, Aleksandar Valjarević and Sylvie Sahal-Bréchot

Atoms 2017, 5(3), 27; https://doi.org/10.3390/atoms5030027 - 8 Sep 2017

Cited by 1 | Viewed by 3173

Abstract

Using the semi-classical perturbation approach in the impact approximation, full width at half maximum and shift have been determined for eight spectral lines of Ar VII, for broadening by electron-, proton-, and He III-impacts. The results are provided for temperatures from 20,000 K [...] Read more.

Using the semi-classical perturbation approach in the impact approximation, full width at half maximum and shift have been determined for eight spectral lines of Ar VII, for broadening by electron-, proton-, and He III-impacts. The results are provided for temperatures from 20,000 K to 500,000 K, and for an electron density of

10^{18}

cm

^{- 3}

. The obtained results will be included in the STARK-B database, which is also in the virtual atomic and molecular data center (VAMDC). Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

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Open AccessFeature PaperArticle

Stark Widths of Ar II Spectral Lines in the Atmospheres of Subdwarf B Stars

by Rafik Hamdi, Nabil Ben Nessib, Sylvie Sahal Bréchot and Milan S. Dimitrijević

Atoms 2017, 5(3), 26; https://doi.org/10.3390/atoms5030026 - 7 Sep 2017

Cited by 16 | Viewed by 3556

Abstract

Stark broadening parameters are of interest for many problems in astrophysics and laboratory plasmas investigation. Ar II spectral lines are observed in many kinds of stellar atmospheres such as the atmospheres of B-Type stars and subdwarf B stars. In this work, we present [...] Read more.

Stark broadening parameters are of interest for many problems in astrophysics and laboratory plasmas investigation. Ar II spectral lines are observed in many kinds of stellar atmospheres such as the atmospheres of B-Type stars and subdwarf B stars. In this work, we present theoretical Stark widths for Ar II spectral lines. We use the impact semiclassical perturbation approach. Our results are compared with the available experimental values. Finally, the importance of the Stark broadening mechanism is studied in atmospheric conditions of subdwarf B stars. Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

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Open AccessFeature PaperReview

Symmetric Atom–Atom and Ion–Atom Processes in Stellar Atmospheres

by Vladimir A. Srećković, Ljubinko M. Ignjatović and Milan S. Dimitrijević

Atoms 2018, 6(1), 1; https://doi.org/10.3390/atoms6010001 - 21 Dec 2017

Cited by 6 | Viewed by 3886

Abstract

We present the results of the influence of two groups of collisional processes (atom–atom and ion–atom) on the optical and kinetic properties of weakly ionized stellar atmospheres layers. The first type includes radiative processes of the photodissociation/association and radiative charge exchange, the second [...] Read more.

We present the results of the influence of two groups of collisional processes (atom–atom and ion–atom) on the optical and kinetic properties of weakly ionized stellar atmospheres layers. The first type includes radiative processes of the photodissociation/association and radiative charge exchange, the second one the chemi-ionisation/recombination processes with participation of only hydrogen and helium atoms and ions. The quantitative estimation of the rate coefficients of the mentioned processes were made. The effect of the radiative processes is estimated by comparing their intensities with those of the known concurrent processes in application to the solar photosphere and to the photospheres of DB white dwarfs. The investigated chemi-ionisation/recombination processes are considered from the viewpoint of their influence on the populations of the excited states of the hydrogen atom (the Sun and an M-type red dwarf) and helium atom (DB white dwarfs). The effect of these processes on the populations of the excited states of the hydrogen atom has been studied using the general stellar atmosphere code, which generates the model. The presented results demonstrate the undoubted influence of the considered radiative and chemi- ionisation/recombination processes on the optical properties and on the kinetics of the weakly ionized layers in stellar atmospheres. Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

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Open AccessFeature PaperProject Report

Photometric and Polarimetric Interpretation of Blazar AO 0235+164 Behaviour

by Elena Shablovinskaya

Atoms 2017, 5(4), 39; https://doi.org/10.3390/atoms5040039 - 19 Oct 2017

Viewed by 3310

Abstract

Among the great number of controversial issues, the most topical one both for theoretical and observational astrophysics presently is a problem of active galactic nuclei investigation. To explain the behaviour of blazar AO 0235+164, which has been under observation at the LX200 telescope [...] Read more.

Among the great number of controversial issues, the most topical one both for theoretical and observational astrophysics presently is a problem of active galactic nuclei investigation. To explain the behaviour of blazar AO 0235+164, which has been under observation at the LX200 telescope (SPbSU) since 2002, the method of analyzing developed by V.A. Hagen-Thorn and S.G. Marchenko was applied. It is based on the assumption that in the case of observational data lying on the straight line in the absolute Stokes parameters space

{I, Q, U}

(for polarimetry) and the fluxes space

{F_{1}, . . F_{n}}

(for photometry), relative Stokes parameters and relative flux ratios stay unchanged , and consequently, only one source is corresponding to the variability of general value of flux. In this paper, the photometric and polarimetric interpretation of blazar behaviour is presented. Furthermore, the flux and flux–flux diagrams are obtained for three periods of object monitoring: 2006–2007 and 2008–2009 (outbursts) and 2009–2016 (decline with 2015 outburst). Full article

(This article belongs to the Special Issue Spectral Line Shapes in Astrophysics and Related Topics)

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