Principles of atomic spectra

The Virtual Atomic and Molecular Data Centre (VAMDC) Consortium is a worldwide consortium which federates atomic and molecular databases through an e-science infrastructure and an organisation to support this activity. About 90% of the inter-connected databases handle data that are used for the interpretation of astronomical spectra and for modelling in many fields of astrophysics. Recently the VAMDC Consortium has connected databases from the radiation damage and the plasma communities, as well as promoting the publication of data from Indian institutes. This paper describes how the VAMDC Consortium is organised for the optimal distribution of atomic and molecular data for scientific research. It is noted that the VAMDC Consortium strongly advocates that authors of research papers using data cite the original experimental and theoretical papers as well as the relevant databases.

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The virtual atomic and molecular data centre (VAMDC) consortium

The measurement of stellar properties such as chemical compositions, masses and ages, through stellar spectra, is a fundamental problem in astrophysics. Progress in the understanding, calculation and measurement of atomic properties and processes relevant to the high-accuracy analysis of F-, G-, and K-type stellar spectra is reviewed, with particular emphasis on abundance analysis. This includes fundamental atomic data such as energy levels, wavelengths, and transition probabilities, as well as processes of photoionisation, collisional broadening and inelastic collisions. A recurring theme throughout the review is the interplay between theoretical atomic physics, laboratory measurements, and astrophysical modelling, all of which contribute to our understanding of atoms and atomic processes, as well as to modelling stellar spectra.

Accurate abundance analysis of late-type stars: advances in atomic physics

A review of the models used for the calculation of the Stark broadening spectrum for plasmas is presented. The aim is to provide an overview of the related theories using a simple formalism, useful for an introduction to the study of this phenomenon, which is encountered in plasma diagnostics. A historical development is followed and some of the problems that are currently under investigation are mentioned.

https://iopscience.iop.org/article/10.1088/0022-3727/47/34/343001/pdf

Stark broadening models for plasma diagnostics

Accurate spectroscopic diagnostics and modeling require the knowledge of numerous collisional line profiles. Access to such data via an online database has become indispensable. The STARK-B database is aimed at meeting these needs for widths and shifts of isolated lines of neutral and ionized elements due to electron and ion impacts. This database of the Paris Observatory is a result of scientific cooperation between S Sahal-Brechot (LERMA) and M S Dimitrijevic (AOB). Access to it is free, and it was opened online at the end of 2008. STARK-B is a node of the Virtual Atomic and Molecular Data Centre (VAMDC) and thus complies with VAMDC and Virtual Observatory standards. VAMDC is a European Union-funded collaboration among groups involved in the generation and use of interoperable atomic and molecular data. STARK-B now contains all our semiclassical-perturbation (SCP) calculated data for more than 123 neutral or ionized elements as published in international refereed journals. It is devoted to modeling and spectroscopic diagnostics of stellar atmospheres and envelopes, laboratory plasmas, laser equipment, and technological plasmas. Hence, the range of temperatures and densities covered by the tables is broad and depends on the ionization degree of the radiating atom. The modified semiempirical (MSE) results of calculations have begun to be implemented. In this paper, we highlight the key points of the method and the assumptions used in the calculations, which have lately been revisited. Then we present the database and its recent developments, as well as our ongoing work and our plans for the future.

http://iopscience.iop.org/article/10.1088/0031-8949/90/5/054008/pdf

The STARK-B database VAMDC node: a repository for spectral line broadening and shifts due to collisions with charged particles

We present, in this work a simple analytical expression of line emission in weakly non ideal plasma using a simplified quantum model. This formalism allows to explain the variations of the line widths with the density in a weakly non ideal plasma. We apply this model to plasma neutral helium lines HeI 6678 A and HeI 5876 A and explain the non linearity of the line width.

/pdf/quantum-model-of-emission-in-a-weakly-non-ideal-plasma-460n5qa2na.pdf

Quantum model of emission in a weakly non ideal plasma

The aim of this work is to theoretically determine Stark broadening parameters of 510554, 570024, 578213, 327396 and 324754 A neutral copper spectral lines Our results are compared with available experimental and other theoretical data The results obtained are also used for the continuation of our investigation of the temperature dependence of Stark widths of neutral atom spectral lines in order to improve existing methods for the scaling of Stark broadening parameters with temperature

https://iopscience.iop.org/article/10.1088/0031-8949/82/05/055301/pdf

Stark broadening calculations of neutral copper spectral lines and temperature dependence

Quantum mechanical results for the electron impact Stark widths of the 3s–3p transitions in ten Li-like ions from C IV to P XIII are carried out. The atomic structure is obtained through a
scaled Thomas-Fermi-Dirac-Amaldi potential (SST numerical code) with relativistic corrections. The distorted wave method is used for the calculation of the S-Matrix, and Feshbach resonances are included by means of the Gailitis method. A comparison with other theoretical and available experimental results is done. Except for Ne VIII, we find that the agreement between our quantum results and the experiments gets better when Z increases, which is not the case for the available
close-coupling quantum ones. The behavior of the Stark width with the charge Z and the electron temperature Te is also studied and in contrast to previous studies, an improved agreement
with experimental Z-scaling is obtained. We show that the relative difference between widths of the two fine structure lines of the same multiplet increases with Z from 0.5% for C IV to
about 12% for P XIII, proving the increasing importance of fine structure effects. The importance of the Feshbach resonances is discussed and a comparison with available semi-classical perturbation results is given.

Quantum Stark broadening of 3s–3p spectral lines in Li-like ions; Z-scaling and comparison with semi-classical perturbation theory

Using the semiclassical perturbation approach by Sahal-Brechot (Astron. Astrophys. 1 91 (1969), 2 322 (1969), 35 321 (1974), 245 322 (1991)) updated by Dimitrijevic and Sahal-Brechot (J. Quant. Spectrosc. Radiat. Transf. 31 301 (1984), Physica Scripta 52 41 (1995)), we have calculated electronic and ionic widths and shifts of several O I spectral lines. We have input the TOPbase (Opacity Project) sophisticated atomic structure data into the Sahal-Brechot's computer code. Then we have compared our results with those of available experiments and with Griem's (1974) theoretical data. We show that our results are improved with the use of TOPbase, especially for the widths.

http://iopscience.iop.org/article/10.1088/0031-8949/54/6/010/pdf

N. Ben Nessib

Papers

The STARK-B database VAMDC node: a repository for spectral line broadening and shifts due to collisions with charged particles

Quantum model of emission in a weakly non ideal plasma

Stark broadening calculations of neutral copper spectral lines and temperature dependence

Quantum Stark broadening of 3s–3p spectral lines in Li-like ions; Z-scaling and comparison with semi-classical perturbation theory

Stark broadening of neutral oxygen lines in the impact and quasistatic approximations