Absorption-line spectroscopy is a powerful tool used to estimate element abundances in both the nearby and distant universe. The accuracy of the abundances thus derived is naturally limited by the accuracy of the atomic data assumed for the spectral lines. We have recently started a project to perform new extensive atomic data calculations used for optical/UV spectral lines in the plasma modeling code Cloudy using state of the art quantal calculations. Here, we demonstrate our approach by focussing on S II, an ion used to estimate metallicities for Milky Way interstellar clouds as well as distant damped Lyman-alpha (DLA) and sub-DLA absorber galaxies detected in the spectra of quasars and gamma-ray bursts. We report new extensive calculations of a large number of energy levels of S II, and the line strengths of the resulting radiative transitions. Our calculations are based on the configuration interaction approach within a numerical Hartree-Fock framework, and utilize both non-relativistic and quasirelativistic one-electron radial orbitals. The results of these new atomic calculations are then incorporated into Cloudy and applied to a lab plasma, and a typical DLA, for illustrative purposes. The new results imply relatively modest changes (0.04 dex) to the metallicities estimated from S II in past studies. These results will be readily applicable to other studies of S II in the Milky Way and other galaxies.

/pdf/atomic-data-for-s-ii-toward-better-diagnostics-of-chemical-3dqd7wcend.pdf

Atomic data for s ii—toward better diagnostics of chemical evolution in high-redshift galaxies

Highly charged ions play a crucial role in magnetic fusion plasmas. These plasmas are excellent sources for producing highly charged ions and copious amounts of radiation for studying their atomic properties. These studies include calibration of density diagnostics, x-ray production by charge exchange, line identifications and accurate wavelength measurements, and benchmark data for ionization balance calculations. Studies of magnetic fusion plasmas also consume a large amount of atomic data, especially in order to develop new spectral diagnostics. Examples we give are the need for highly accurate wavelengths as references for measurements of bulk plasma motion, the need for accurate line excitation rates that encompass both electron-impact excitation and indirect line formation processes, for accurate position and resonance strength information of dielectronic recombination satellite lines that may broaden or shift diagnostic lines or that may provide electron temperature information, and the need for accurate ionization balance calculations. We show that the highly charged ions of several elements are of special current interest to magnetic fusion, notably highly charged ions of argon, iron, krypton, xenon, and foremost of tungsten. The electron temperatures thought to be achievable in the near future may produce W70+ ions and possibly ions with even higher charge states. This means that all but a few of the most highly charged ions are of potential interest as plasma diagnostics or are available for basic research.

Highly Charged Ions in Magnetic Fusion Plasmas: Research Opportunities and Diagnostic Necessities

Theoretical energy level spectra and transition data for 4p{sup 6}4d, 4p{sup 6}4f and 4p{sup 5}4d{sup 2} configurations of W{sup 37+} ion

Theoretical energy level spectra and transition data for 4p64d2, 4p64d4f, and 4p54d3 configurations of W36+

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.

https://www.mdpi.com/2218-2004/5/4/37/pdf

Discrepancies in Atomic Data and Suggestions for Their Resolutions

http://www.adas.ac.uk/2015talks/2015_ADAS_KAggarwal.pdf

Energy levels and radiative rates for transitions in Cr-like Co IV and Ni V

Ab initio oscillator strengths and transition probabilities in aluminum-like calcium, Ca VIII

Ab initio oscillator strengths and transition probabilities of transitions from 2s22p23l and 2s2p33l in S X

Energy levels and radiative rates for transitions in Cr-like Kr XIII, Tc XX and Xe XXXI

The ab initio quasirelativistic Hartree–Fock approximation was used to determine spectroscopic parameters for the multicharged tungsten ions with an open 4p shell. The configuration interaction method based on the transformed radial orbitals was applied to include the electron-correlation effects. The relativistic effects were taken into account in the Breit–Pauli approximation for the quasirelativistic Hartree–Fock radial orbitals. The complete energy level spectra were calculated for the 4s 2 4p N , 4s 2 4p N–1 4d and 4s4p N+1 configurations of the tungsten ions from W 43+ to W 38+ .

R. Karpuškienė

Papers

Energy levels and radiative rates for transitions in Cr-like Co IV and Ni V

Ab initio oscillator strengths and transition probabilities in aluminum-like calcium, Ca VIII

Ab initio oscillator strengths and transition probabilities of transitions from 2s22p23l and 2s2p33l in S X

Energy levels and radiative rates for transitions in Cr-like Kr XIII, Tc XX and Xe XXXI

Energy spectra of the tungsten ion 4s24pN, 4s24N–14d and 4s4pN+1 configurations