Special Issue "Current Developments and Applications of Atomic Structure and Radiative Process Investigations"

A special issue of Atoms (ISSN 2218-2004).

Deadline for manuscript submissions: closed (30 June 2018)

Special Issue Editor

Guest Editor
Dr. Pascal Quinet

Physique Atomique et Astrophysique, Université de Mons, B-7000 Mons, Belgium ; IPNAS, Université de Liège, B-4000 Liège, Belgium
Website | E-Mail
Interests: atomic physics; atomic structure; atomic spectra; radiative and collisional processes

Special Issue Information

Dear Colleagues,

The study of electronic structures and radiative processes in atoms, from neutrals to highly ionized species, has known a considerable development during the past few decades; new contributions arise from both experiment and theory. This appreciable progress was aided by greatly-improved, or even entirely-new, laboratory equipment, and by vastly expanded computer power, which has made possible the development of widely-refined atomic structure codes.

On the experimental side, the recent developments now allow measuring of atomic parameters with a very high accuracy. This is extremely useful to test the predictive power of theoretical models and to obtain a reliable absolute scale for spectroscopic data, such as radiative transition probabilities. Using laser spectroscopy, it is now possible to measure radiative lifetimes for excited atomic states with an accuracy of a few percent for many-electron atomic systems, thanks to the selective excitation avoiding cascading problems. In addition, the development of ion traps has opened the way towards new accurate experimental studies of much more acute effects on the atomic structures, such as hyperfine or isotope effects. Some derivatives of these devices, such as storage rings or electron-beam ion traps, are also in use. The former ones are very useful for the investigation of metastable states in lowly ionized atoms, of which lifetimes may range from milliseconds to years, while the latter ones are dedicated to the production and the analysis of highly charged ions.

On the theoretical side, an intense effort over the last few years has been directed toward developing methods to accurately and simultaneously account for relativistic and correlation effects in many-electron systems, both effects being intertwined in heavy atoms and ions. All the current state-of-the-art computational techniques developed for modeling complex atomic structures present the advantage of being complementary, since they employ different treatments of, for example, configuration interaction, relativistic effects and atomic orbital optimization. This complementarity offers a unique opportunity to assess the reliability of the theoretical results when experimental measurements are unavailable.

Accurate atomic structure and radiative data are essential ingredients for a wide range of research fields, as well as for major technological applications. Areas from laboratory spectroscopy to quantum processing, from plasma research applications in nuclear fusion to lighting research, as well as astrophysics and cosmology, critically depend on such data. However, many spectroscopic parameters still exhibit inconsistencies and inaccuracies, so significant efforts are continuing to improve data quality. Additionally, a substantial body of much-needed data is still absent from the published literature and from databases.

This Special Issue of Atoms will highlight the need for continuing studies on the atomic structures and radiative processes and will present some of the most recent theoretical and experimental works performed in this research field.

Dr. Pascal Quinet
Guest Editor

Manuscript Submission Information

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Keywords

  • Atomic physics
  • atomic structure
  • atomic spectra
  • Energy levels
  • Radiative processes
  • Transition probabilities
  • Oscillator strengths
  • Radiative lifetimes
  • Hyperfine structure
  • Isotope shifts
  • Application of radiative data in astrophysics
  • Application of radiative data in plasma physics

Published Papers (7 papers)

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Research

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Open AccessArticle Parametric Calculations of Radiative Decay Rates for Magnetic Dipole and Electric Quadrupole Transitions in Tm IV, Yb V, and Er IV
Received: 18 August 2018 / Revised: 7 September 2018 / Accepted: 9 September 2018 / Published: 12 September 2018
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Abstract
Semi-empirical transition probabilities for magnetic dipole (M1) and electric quadrupole (E2) emission lines have been derived from parametric studies of experimental energy levels in Tm3+ (Tm IV), Yb4+ (Yb V), and Er3+ (Er IV), using Cowan codes. Results are compared
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Semi-empirical transition probabilities for magnetic dipole (M1) and electric quadrupole (E2) emission lines have been derived from parametric studies of experimental energy levels in Tm3+ (Tm IV), Yb4+ (Yb V), and Er3+ (Er IV), using Cowan codes. Results are compared with those existing from ab initio calculations or from more sophisticated semi-empirical calculations. Satisfactory agreements show that simple parametric calculations can provide good predictions on line intensities, provided that experimental levels are available, allowing reliable fits of energy parameters. Full article
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Open AccessArticle Extended Analysis of Ar III and Ar IV
Received: 18 July 2018 / Revised: 10 August 2018 / Accepted: 16 August 2018 / Published: 21 August 2018
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Abstract
A pulsed discharge light source was used to study the two and three times ionized argon (Ar II, Ar III) spectra in the 480–6218 Å region. A set of 129 transitions of Ar III and 112 transitions of Ar IV were classified for
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A pulsed discharge light source was used to study the two and three times ionized argon (Ar II, Ar III) spectra in the 480–6218 Å region. A set of 129 transitions of Ar III and 112 transitions of Ar IV were classified for the first time. We extended the analysis of Ar III to five new energy levels belonging to 3s23p34d, 3s23p35s odd configurations. For Ar IV, 10 new energy levels of the 3s23p23d and 3s23p24p even and odd configurations, respectively, are presented. For the prediction of energy levels, line transitions, and transition probabilities, relativistic Hartree–Fock calculations were used. Full article
Open AccessFeature PaperArticle Intercombination Transitions in the n = 4 Shell of Zn-, Ga-, and Ge-Like Ions of Elements Kr through Xe
Received: 27 April 2018 / Revised: 18 July 2018 / Accepted: 27 July 2018 / Published: 31 July 2018
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Abstract
Earlier beam-foil measurements have targeted 4s-4p intercombination transitions in the Zn-, Ga- and Ge-like ions of Nb (Z=41), Mo (Z=42), Rh (Z=44), Ag (Z=47) and I (
[...] Read more.
Earlier beam-foil measurements have targeted 4s-4p intercombination transitions in the Zn-, Ga- and Ge-like ions of Nb (Z=41), Mo (Z=42), Rh (Z=44), Ag (Z=47) and I (Z=53). At the time, the spectra were calibrated with literature data on prominent lines in the Cu- and Zn-like ions. Corresponding literature data on the intercombination transitions in Ga- and Ge-like ions were largely lacking, which caused some ambiguity in the line identifications. We review the (mostly computational) progress made since. We find that a consistent set of state-of-the-art computations of Ga- and Ge-like ions would be highly desirable for revisiting the beam-foil data and the former line identifications for the elements from Kr (Z=36) to Xe (Z=54). We demonstrate that the literature data for these two isoelectronic sequences are insufficient, and we contribute reference computations in the process. We discuss the option of electron beam ion trap measurements as an alternative to the earlier use of classical light sources, beam-foil interaction and laser-produced plasmas, with the example of Xe (Z=54). Full article
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Open AccessFeature PaperArticle Systematic Observation of EUV Spectra from Highly Charged Lanthanide Ions in the Large Helical Device
Received: 27 March 2018 / Revised: 24 April 2018 / Accepted: 25 April 2018 / Published: 1 May 2018
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Abstract
We have systematically observed extreme ultraviolet (EUV) spectra from highly charged ions of nine lanthanide elements with atomic numbers from 60–70 in optically thin plasmas produced in the Large Helical Device (LHD). Discrete spectral features with isolated lines from relatively higher charge states
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We have systematically observed extreme ultraviolet (EUV) spectra from highly charged ions of nine lanthanide elements with atomic numbers from 60–70 in optically thin plasmas produced in the Large Helical Device (LHD). Discrete spectral features with isolated lines from relatively higher charge states around Cu-like ions are observed under high temperature conditions around 2 keV, while narrowed quasicontinuum features from charge states around Ag-like ions are observed under low temperature conditions below 1 keV. The positions of the lines and the quasicontinuum features systematically move to shorter wavelengths as the atomic number increases. The wavelengths of the main peaks in the quasicontinuum features agree well with those of singlet transitions of Pd-like ions reported previously. We have easily identified discrete spectral lines from Cu-like and Ag-like ions, some of which are experimentally identified for the first time in the LHD. Their wavelengths are compared with theoretical calculations using a GRASP family of atomic codes. The theoretical values are synthesized to the LHD experimental data for the cases of Ag- and Pd-like ions. Full article
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Open AccessFeature PaperArticle The Effect of Correlation on Spectra of the Lanthanides: Pr3+
Received: 2 February 2018 / Revised: 21 February 2018 / Accepted: 21 February 2018 / Published: 25 February 2018
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Abstract
The effect of correlation on the spectra of lanthanide ions has been investigated using variational methods based on multiconfiguration Dirac–Hartree–Fock (MCDHF) theory. Results from several computational models are reported for Pr3+. The first assumes an inactive Cd-like 4d10 core
[...] Read more.
The effect of correlation on the spectra of lanthanide ions has been investigated using variational methods based on multiconfiguration Dirac–Hartree–Fock (MCDHF) theory. Results from several computational models are reported for Pr3+. The first assumes an inactive Cd-like 4 d 10 core with valence electrons in 4 f 2 5 s 2 5 p 6 subshells. Additional models extend correlation to include core effects. It is shown that, with such models, the difference between computed energy levels and those from observed data increases with the energy of the level, suggesting that correlation among outer electrons should also be based on the correlated core of excited configuration state functions (CSFs). Some M1 transition probabilities are reported for the most accurate model and compared with predictions obtained from semi-empirical methods. Full article
Open AccessArticle Spectrum of Sn5+ in the Region 500–1300 Å
Received: 3 October 2017 / Revised: 7 November 2017 / Accepted: 8 November 2017 / Published: 18 November 2017
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Abstract
The spectrum of tin, excited in a vacuum spark, was recorded in the region 500–1131 Å on a 6.65-m normal incidence spectrograph. The transitions between 4d85s, 4d86s, 4d85p and 4d85d excited configurations in Sn VI
[...] Read more.
The spectrum of tin, excited in a vacuum spark, was recorded in the region 500–1131 Å on a 6.65-m normal incidence spectrograph. The transitions between 4d85s, 4d86s, 4d85p and 4d85d excited configurations in Sn VI were studied. More than 500 lines of the 4d85p–4d85d and 4d85p–4d86s were identified with the aid of the Cowan code calculations. 67 energy levels (out of 70 possible levels of the 4d85d configuration) and all but two 4d86s levels were found. The wavelength of the 4d85s–4d85p transitions in the region 839–1131 Å were re-measured and supplemented by Sn VI lines in the region 1131–1300 Å measured previously by Srivastava et al. (1977) for optimisation of the energy level values. The SnVI line list in the region 500–1300 Å contains now 741 lines with calculated transition probabilities. Full article
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Review

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Open AccessReview Application of Laboratory Atomic Physics to Some Significant Stellar Chemical Composition Questions
Received: 27 July 2018 / Revised: 22 August 2018 / Accepted: 23 August 2018 / Published: 27 August 2018
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Abstract
This brief review highlights some current issues in Galactic stellar nucleosynthesis, and some recent laboratory studies by the Wisconsin atomic physics group that have direct application to stellar spectroscopy to advance our understanding of the chemical evolution of our Galaxy. The relevant publication
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This brief review highlights some current issues in Galactic stellar nucleosynthesis, and some recent laboratory studies by the Wisconsin atomic physics group that have direct application to stellar spectroscopy to advance our understanding of the chemical evolution of our Galaxy. The relevant publication history of the lab studies are summarized, and investigations into the abundances of neutron-capture and iron-peak elements in low metallicity stars are described. Finally, new initiatives in near-infrared spectroscopy are briefly explored. Full article
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