Photometric and Polarimetric Interpretation of Blazar AO 0235+164 Behaviour*Atoms* **2017**, *5*(4), 39; doi:10.3390/atoms5040039 - 19 October 2017**Abstract **

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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

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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 $\{{F}_{1},..\phantom{\rule{4pt}{0ex}}{F}_{n}\}$ (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).
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THz/Infrared Double Resonance Two-Photon Spectroscopy of HD^{+} for Determination of Fundamental Constants*Atoms* **2017**, *5*(4), 38; doi:10.3390/atoms5040038 - 12 October 2017**Abstract **

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A double resonance two-photon spectroscopy scheme is discussed to probe jointly rotational and rovibrational transitions of ensembles of trapped HD^{+} ions. The two-photon transition rates and lightshifts are calculated with the two-photon tensor operator formalism. The rotational lines may be observed with

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A double resonance two-photon spectroscopy scheme is discussed to probe jointly rotational and rovibrational transitions of ensembles of trapped HD^{+} ions. The two-photon transition rates and lightshifts are calculated with the two-photon tensor operator formalism. The rotational lines may be observed with sub-Doppler linewidth at the hertz level and good signal-to-noise ratio, improving the resolution in HD^{+} spectroscopy beyond the 10^{−12} level. The experimental accuracy, estimated at the 10^{−12} level, is comparable with the accuracy of theoretical calculations of HD^{+} energy levels. An adjustment of selected rotational and rovibrational HD^{+} lines may add clues to the proton radius puzzle, may provide an independent determination of the Rydberg constant, and may improve the values of proton-to-electron and deuteron-to-proton mass ratios beyond the 10^{−11} level.
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Discrepancies in Atomic Data and Suggestions for Their Resolutions*Atoms* **2017**, *5*(4), 37; doi:10.3390/atoms5040037 - 9 October 2017**Abstract **

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The analysis and modelling of a range of plasmas (for example, astrophysical, laser- produced and fusion) require atomic data for a number of parameters, such as energy levels, radiative rates and electron impact excitation rates, or equivalently, the effective collision strengths. Such data

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The analysis and modelling of a range of plasmas (for example, astrophysical, laser- produced and fusion) require atomic data for a number of parameters, such as energy levels, radiative rates and electron impact excitation rates, or equivalently, the effective collision strengths. Such data are desired for a wide range of elements and their many ions, although all elements are not useful for all types of plasmas. Since measurements of atomic data are mostly confined to only a few energy levels of some ions, calculations for all parameters are highly important. However, often, there are large discrepancies among different calculations for almost all parameters, which makes it difficult to apply the data with confidence. Many such discrepancies (and the possible remedies) were discussed earlier (*Fusion Sci. Technol.***2013**, *63*, 363). Since then, many more anomalies for almost all of these atomic parameters have been noticed. Therefore, this paper is a revisit of various atomic parameters to highlight the large discrepancies, their possible sources and some suggestions to avoid these, so that comparatively more accurate and reliable atomic data may be available in the future.
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Stark-Zeeman Line Shape Modeling for Magnetic White Dwarf and Tokamak Edge Plasmas: Common Challenges*Atoms* **2017**, *5*(4), 36; doi:10.3390/atoms5040036 - 4 October 2017**Abstract **

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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

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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.
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Line Shape Modeling for the Diagnostic of the Electron Density in a Corona Discharge*Atoms* **2017**, *5*(4), 35; doi:10.3390/atoms5040035 - 28 September 2017**Abstract **

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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

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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.
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Effect of Turbulence on Line Shapes in Astrophysical and Fusion Plasmas*Atoms* **2017**, *5*(4), 34; doi:10.3390/atoms5040034 - 25 September 2017**Abstract **

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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

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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.
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Stark Broadening from Impact Theory to Simulations*Atoms* **2017**, *5*(3), 32; doi:10.3390/atoms5030032 - 20 September 2017**Abstract **

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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

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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.
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Quasar Black Hole Mass Estimates from High-Ionization Lines: Breaking a Taboo?*Atoms* **2017**, *5*(3), 33; doi:10.3390/atoms5030033 - 20 September 2017**Abstract **

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Can high ionization lines such as CIV$\lambda $ 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

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Can high ionization lines such as CIV$\lambda $ 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$\lambda $ 1549 line profiles. In this contribution, we first summarize the evidence suggesting that the FWHM of low-ionization lines like H$\beta $ and MgII$\lambda $ 2800 provide reliable virial broadening estimators over a broad range of luminosity. We confirm that the line widths of CIV$\lambda $ 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$\lambda $ 1549 for Eddington ratio and luminosity effects that, however, remains cumbersome to apply in practice. Intermediate ionization lines (IP ∼ 20–30 eV; AlIII$\lambda $ 1860 and SiIII]$\lambda $ 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.
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Radiative and Collisional Molecular Data and Virtual Laboratory Astrophysics*Atoms* **2017**, *5*(3), 31; doi:10.3390/atoms5030031 - 19 September 2017**Abstract **

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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

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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.
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Identification and Plasma Diagnostics Study of Extreme Ultraviolet Transitions in Highly Charged Yttrium*Atoms* **2017**, *5*(3), 30; doi:10.3390/atoms5030030 - 18 September 2017**Abstract **

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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

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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 $\Delta $ *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, 2*s*–$2{p}_{1/2}$ and 2*s*–2${p}_{3/2}$ , and the Na-like D lines, 3*s*–$3{p}_{1/2}$ and 3*s*–$3{p}_{3/2}$ , 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.
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Stark Widths of Na IV Spectral Lines*Atoms* **2017**, *5*(3), 29; doi:10.3390/atoms5030029 - 18 September 2017**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/ ).
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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 - 13 September 2017**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.
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Semiclassical Stark Broadening Parameters of Ar VII Spectral Lines*Atoms* **2017**, *5*(3), 27; doi:10.3390/atoms5030027 - 8 September 2017**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).
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Stark Widths of Ar II Spectral Lines in the Atmospheres of Subdwarf B Stars*Atoms* **2017**, *5*(3), 26; doi:10.3390/atoms5030026 - 7 September 2017**Abstract **

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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

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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.
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Wavelengths of the Self-Photopumped Nickel-Like *4f*^{1}*P*_{1}*→4d*^{1}*P*_{1} X-ray Laser Transitions*Atoms* **2017**, *5*(3), 25; doi:10.3390/atoms5030025 - 13 July 2017**Abstract **

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The energies for the lower *3d*_{3/2}4d_{3/2} [J = 1] and upper *3d*_{3/2}4f_{5/2} [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 *3d*_{3/2}4d_{3/2} [J = 1] and upper *3d*_{3/2}4f_{5/2} [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.
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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 - 26 June 2017**Abstract **

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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 $5{f}^{\mathrm{}}$

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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 $5{f}^{3}7{s}^{2}+5{f}^{3}6d7s+5{f}^{3}6{d}^{2}+5{f}^{4}7p+5{f}^{5}$ 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 $5{f}^{4}7s,5{f}^{4}6d,5{f}^{2}6{d}^{2}7s,5{f}^{2}6d7{s}^{2}$ 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 $5{f}^{3}7s7p+5{f}^{3}6d7p$ 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 $5{f}^{3}6d7p$ ${{(}^{4}I)}^{6}K(J=5.5)$ at 39113.98 $\pm 0.1$ cm${}^{-1}$ .
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The Third Spectrum of Indium: In III*Atoms* **2017**, *5*(2), 23; doi:10.3390/atoms5020023 - 13 June 2017**Abstract **

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The present investigation reports on the extended study of the third spectrum of indium (In III). This spectrum was previously analyzed in many articles, but, nevertheless, this study represents a significant extension of the previous analyses. The main new contribution is connected to

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The present investigation reports on the extended study of the third spectrum of indium (In III). This spectrum was previously analyzed in many articles, but, nevertheless, this study represents a significant extension of the previous analyses. The main new contribution is connected to the observation of transitions involving core-excited configurations. Previous data are critically evaluated and in some cases are corrected. The spectra were recorded on 3-m as well as on 10.7-m normal incidence spectrographs using a triggered spark source. Theoretical calculations were made with Cowan’s code. The analysis results in the identifications of 70 spectral lines and determination of 24 new energy levels. In addition, the manuscript represents a compilation of all presently available data on In III.
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Detailed Opacity Calculations for Astrophysical Applications*Atoms* **2017**, *5*(2), 22; doi:10.3390/atoms5020022 - 30 May 2017**Abstract **

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Nowadays, several opacity codes are able to provide data for stellar structure models, but the computed opacities may show significant differences. In this work, we present state-of-the-art precise spectral opacity calculations, illustrated by stellar applications. The essential role of laboratory experiments to check

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Nowadays, several opacity codes are able to provide data for stellar structure models, but the computed opacities may show significant differences. In this work, we present state-of-the-art precise spectral opacity calculations, illustrated by stellar applications. The essential role of laboratory experiments to check the quality of the computed data is underlined. We review some X-ray and XUV laser and Z-pinch photo-absorption measurements as well as X-ray emission spectroscopy experiments involving hot dense plasmas produced by ultra-high-intensity laser irradiation. The measured spectra are systematically compared with the fine-structure opacity code SCO-RCG. The focus is on iron, due to its crucial role in understanding asteroseismic observations of *β* Cephei-type and Slowly Pulsating B stars, as well as of the Sun. For instance, in *β* Cephei-type stars, the iron-group opacity peak excites acoustic modes through the “kappa-mechanism”. Particular attention is paid to the higher-than-predicted iron opacity measured at the Sandia Z-machine at solar interior conditions. We discuss some theoretical aspects such as density effects, photo-ionization, autoionization or the “filling-the-gap” effect of highly excited states.
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Configuration Interaction Effects in Unresolved 5p^{6}5d^{N+1}−5p^{5}5d^{N+2}+5p^{6}5d^{N}5f^{1} Transition Arrays in Ions Z = 79–92*Atoms* **2017**, *5*(2), 20; doi:10.3390/atoms5020020 - 21 May 2017**Abstract **

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Configuration interaction (CI) effects can greatly influence the way in which extreme ultraviolet (EUV) and soft X-ray (SXR) spectra of heavier ions are dominated by emission from unresolved transition arrays (UTAs), the most intense of which originate from *Δn = 0, 4p*^{6}

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Configuration interaction (CI) effects can greatly influence the way in which extreme ultraviolet (EUV) and soft X-ray (SXR) spectra of heavier ions are dominated by emission from unresolved transition arrays (UTAs), the most intense of which originate from *Δn = 0, 4p*^{6}4d^{N+1}−*4p*^{5}4d^{N+2}+4p^{6}4d^{N}4f^{1} transitions. Changing the principle quantum number *n*, from 4 to 5, changes the origin of the UTA from *Δn = 0, 4p*^{6}4d^{N+1}−*4p*^{5}4d^{N+2}+4p^{6}4d^{N}4f^{1} to *Δn = 0, 5p*^{6}5d^{N+1}−*5p*^{5}5d^{N+2}+5p^{6}5d^{N}5f^{1} transitions. This causes unexpected and significant changes in the impact of configuration interaction from that observed in the heavily studied *n = 4 – n = 4* arrays. In this study, the properties of *n = 5* – *n = 5* arrays have been investigated theoretically with the aid of Hartree-Fock with configuration interaction (HFCI) calculations. In addition to predicting the wavelengths and spectral details of the anticipated features, the calculations show that the effects of configuration interaction are quite different for the two different families of *Δn = 0* transitions, a conclusion which is reinforced by comparison with experimental results.
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Inter-Series Interactions on the Atomic Photoionization Spectra Studied by the Phase-Shifted Multichannel-Quantum Defect Theory*Atoms* **2017**, *5*(2), 21; doi:10.3390/atoms5020021 - 20 May 2017**Abstract **

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Development in mathematical formulations of parameterizing the resonance structures using the phase-shifted multichannel quantum defect theory (MQDT) and their use in analyzing the effect of inter-series interactions on the autoionizing Rydberg spectra is reviewed. Reformulation of the short-range scattering matrix into the form

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Development in mathematical formulations of parameterizing the resonance structures using the phase-shifted multichannel quantum defect theory (MQDT) and their use in analyzing the effect of inter-series interactions on the autoionizing Rydberg spectra is reviewed. Reformulation of the short-range scattering matrix into the form analogous to **S** = **S**_{B}S_{R} in scattering theory are the crucial step in this development. Formulation adopts different directions and goals depending on whether autoionizing series converge to the same limit (degenerate) or to different limits (nondegenerate) because of the different nature of the perturbation. For the nondegenerate case, finding the simplest form of profile index functions of the autoionizing spectra with the minimal number of parameters is the main goal and some results are reviewed. For the degenerate case where perturbation acts uniformly throughout the entire series, isolation of the overlapped autoionizing series into the unperturbed autoionizing series is the key objective in research and some results in that direction are reviewed.
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