Current Developments and Applications of Atomic Structure and Radiative Process Investigations

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

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