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Atoms, Volume 5, Issue 3 (September 2017)

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Research

Open AccessArticle Spectrum of Singly Charged Uranium (U II) : Theoretical Interpretation of Energy Levels, Partition Function and Classified Ultraviolet Lines
Atoms 2017, 5(3), 24; doi:10.3390/atoms5030024
Received: 23 March 2017 / Revised: 8 June 2017 / Accepted: 16 June 2017 / Published: 26 June 2017
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Abstract
In an attempt to improve U II analysis, the lowest configurations of both parities have been interpreted by means of the Racah-Slater parametric method, using Cowan codes. In the odd parity, including the ground state, 253 levels of the interacting configurations 5f
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In an attempt to improve U II analysis, the lowest configurations of both parities have been interpreted by means of the Racah-Slater parametric method, using Cowan codes. In the odd parity, including the ground state, 253 levels of the interacting configurations 5 f 3 7 s 2 + 5 f 3 6 d 7 s + 5 f 3 6 d 2 + 5 f 4 7 p + 5 f 5 are interpreted by 24 free parameters and 64 constrained ones, with a root mean square (rms) deviation of 60 cm 1 . In the even parity, the four known configurations 5 f 4 7 s , 5 f 4 6 d , 5 f 2 6 d 2 7 s , 5 f 2 6 d 7 s 2 and the unknown 5 f 2 6 d 3 form a basis for interpreting 125 levels with a rms deviation of 84 cm 1 . Due to perturbations, the theoretical description of the higher configurations 5 f 3 7 s 7 p + 5 f 3 6 d 7 p remains unsatisfactory. The known and predicted levels of U II are used for a determination of the partition function. The parametric study led us to a re-investigation of high resolution ultraviolet spectrum of uranium recorded at the Meudon Observatory in the late eighties, of which the analysis was unachieved. In the course of the present study, a number of 451 lines of U II has been classified in the region 2344 –2955 Å. One new level has been established as 5 f 3 6 d 7 p ( 4 I ) 6 K ( J = 5.5 ) at 39113.98 ± 0.1 cm 1 . Full article
(This article belongs to the Special Issue Spectra of Ionized Atoms: From Laboratory to Space)
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Open AccessFeature PaperArticle Wavelengths of the Self-Photopumped Nickel-Like 4f 1P1→4d 1P1 X-ray Laser Transitions
Atoms 2017, 5(3), 25; doi:10.3390/atoms5030025
Received: 31 January 2017 / Revised: 6 June 2017 / Accepted: 27 June 2017 / Published: 13 July 2017
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Abstract
The energies for the lower 3d3/24d3/2 [J = 1] and upper 3d3/24f5/2 [J = 1] working levels in the self-photopumped X-ray laser are analyzed along the Ni-like sequence. We have found some irregularities in these energy levels
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The energies for the lower 3d3/24d3/2 [J = 1] and upper 3d3/24f5/2 [J = 1] working levels in the self-photopumped X-ray laser are analyzed along the Ni-like sequence. We have found some irregularities in these energy levels in the range Z = 42–49. The causes of the irregularities are studied. The list of elements that lase on the self-photopumped transition can be extended much further than originally known. We calculate the wavelengths of this transition in Ni-like sequence to Z = 79 using the relativistic perturbation theory with a zero approximation model potential. We estimate the wavelength accuracy for Z > 50 as Δλ/λ ≤ 0.005. Full article
(This article belongs to the Special Issue Spectra of Ionized Atoms: From Laboratory to Space)
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Open AccessFeature PaperArticle Stark Widths of Ar II Spectral Lines in the Atmospheres of Subdwarf B Stars
Atoms 2017, 5(3), 26; doi:10.3390/atoms5030026
Received: 29 August 2017 / Accepted: 4 September 2017 / Published: 7 September 2017
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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
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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 PaperArticle Semiclassical Stark Broadening Parameters of Ar VII Spectral Lines
Atoms 2017, 5(3), 27; doi:10.3390/atoms5030027
Received: 16 August 2017 / Revised: 1 September 2017 / Accepted: 6 September 2017 / Published: 8 September 2017
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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
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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)
Open AccessArticle Radiative Decay Rates for Electric Dipole, Magnetic Dipole and Electric Quadrupole Transitions in Triply Ionized Thulium (Tm IV)
Atoms 2017, 5(3), 28; doi:10.3390/atoms5030028
Received: 2 August 2017 / Revised: 8 September 2017 / Accepted: 11 September 2017 / Published: 13 September 2017
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Abstract
A new set of radiative decay parameters (oscillator strengths, transition probabilities) for spectral lines in triply ionized thulium (Tm IV) has been obtained within the framework of the pseudo-relativistic Hartree-Fock (HFR) approach. The effects of configuration interaction and core-polarization have been investigated in
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A new set of radiative decay parameters (oscillator strengths, transition probabilities) for spectral lines in triply ionized thulium (Tm IV) has been obtained within the framework of the pseudo-relativistic Hartree-Fock (HFR) approach. The effects of configuration interaction and core-polarization have been investigated in detail and the quality of the results has been assessed through a comparison between different HFR physical models. The spectroscopic data listed in the present paper cover electric dipole as well as magnetic dipole and electric quadrupole transitions in a wide range of wavelengths from extreme ultraviolet to near infrared. Full article
Open AccessFeature PaperArticle Stark Widths of Na IV Spectral Lines
Atoms 2017, 5(3), 29; doi:10.3390/atoms5030029
Received: 16 August 2017 / Revised: 8 September 2017 / Accepted: 14 September 2017 / Published: 18 September 2017
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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
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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)
Open AccessFeature PaperArticle Identification and Plasma Diagnostics Study of Extreme Ultraviolet Transitions in Highly Charged Yttrium
Atoms 2017, 5(3), 30; doi:10.3390/atoms5030030
Received: 17 July 2017 / Revised: 8 September 2017 / Accepted: 12 September 2017 / Published: 18 September 2017
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Abstract
Extreme ultraviolet spectra of the L-shell ions of highly charged yttrium (Y26+–Y36+) were observed in the electron beam ion trap of the National Institute of Standards and Technology using a flat-field grazing-incidence spectrometer in the wavelength range
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Extreme ultraviolet spectra of the L-shell ions of highly charged yttrium (Y 26 + –Y 36 + ) were observed in the electron beam ion trap of the National Institute of Standards and Technology using a flat-field grazing-incidence spectrometer in the wavelength range of 4 nm-20 nm. The electron beam energy was systematically varied from 2.3 keV–6.0 keV to selectively produce different ionization stages. Fifty-nine spectral lines corresponding to Δ n = 0 transitions within the n = 2 and n = 3 shells have been identified using detailed collisional-radiative (CR) modeling of the non-Maxwellian plasma. The uncertainties of the wavelength determinations ranged between 0.0004 nm and 0.0020 nm. Li-like resonance lines, 2s 2 p 1 / 2 and 2s–2 p 3 / 2 , and the Na-like D lines, 3s 3 p 1 / 2 and 3s 3 p 3 / 2 , have been measured and compared with previous measurements and calculations. Forbidden magnetic dipole (M1) transitions were identified and analyzed for their potential applicability in plasma diagnostics using large-scale CR calculations including approximately 1.5 million transitions. Several line ratios were found to show strong dependence on electron density and, hence, may be implemented in the diagnostics of hot plasmas, in particular in fusion devices. Full article
(This article belongs to the Special Issue Spectra of Ionized Atoms: From Laboratory to Space)
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Open AccessFeature PaperArticle Radiative and Collisional Molecular Data and Virtual Laboratory Astrophysics
Atoms 2017, 5(3), 31; doi:10.3390/atoms5030031
Received: 4 September 2017 / Revised: 12 September 2017 / Accepted: 13 September 2017 / Published: 19 September 2017
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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
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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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Open AccessFeature PaperArticle Stark Broadening from Impact Theory to Simulations
Atoms 2017, 5(3), 32; doi:10.3390/atoms5030032
Received: 31 August 2017 / Accepted: 11 September 2017 / Published: 20 September 2017
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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
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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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Open AccessFeature PaperArticle Quasar Black Hole Mass Estimates from High-Ionization Lines: Breaking a Taboo?
Atoms 2017, 5(3), 33; doi:10.3390/atoms5030033
Received: 31 August 2017 / Revised: 12 September 2017 / Accepted: 14 September 2017 / Published: 20 September 2017
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Abstract
Can high ionization lines such as CIVλ1549 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
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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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