Institute Isaac Newton of Chile

Newton of, Chile

Institute Isaac Newton of Chile

Newton of, Chile
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Zmerli B.,University of Carthage | Ben Nessib N.,University of Carthage | Dimitrijevic M.S.,Astronomical Observatory | Dimitrijevic M.S.,University of Paris Descartes | And 2 more authors.
Physica Scripta | Year: 2010

The aim of this work is to theoretically determine Stark broadening parameters of 5105.54, 5700.24, 5782.13, 3273.96 and 3247.54 Å 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. © 2010 The Royal Swedish Academy of Sciences.

Sreckovic V.A.,University of Belgrade | Sreckovic V.A.,Institute Isaac Newton of Chile | Mihajlov A.A.,University of Belgrade | Mihajlov A.A.,Institute Isaac Newton of Chile | And 4 more authors.
Astronomy and Astrophysics | Year: 2013

We aim to show the importance of non-elastic excitation and deexcitation processes in He?(n) + He(1s2) collisions with the principal quantum number n ≥ 3 for helium-rich white dwarf atmospheres. We compare the efficiencies of these processes with those of the known non-elastic electron-He?(n) atom processes in the atmospheres of some DB white dwarfs. We show that in significant parts of the considered atmospheres, which contain weakly ionized layers (the ionization degree ≤10?3), the influence of the studied atom- Rydberg atom processes on excited helium atom populations is dominant or at least comparable to the influence of the concurrent electron-He?(n)-atom processes. © 2013 ESO.

Hamdi R.,University of Carthage | Nessib N.B.,King Saud University | Nessib N.B.,University of Carthage | Dimitrijevic M.S.,Astronomical Observatory | And 3 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013

Stark-broadening parameters have been calculated for 114 spectral lines of triply charged lead ion (Pb IV) using semiclassical perturbation approach in the impact approximation. The provided widths and shifts have been obtained for a set of temperatures from 20 000 to 300 000K and an electron density of 1017cm-3. The studied lines correspond to transitions between the configurations 5d10nl-5d10n' l' and 5d96s2-5d10nl. Energy levels and oscillator strengths needed for this calculation have been calculated using a Hartree-Fock relativistic (HFR) approach. Comparison has also been made with available theoretical and experimental results. In addition, the regularity in the 5d106s2S1/2-5d10np2Po 1/2 spectral series has been studied. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.

Sahal-Brechot S.,French National Center for Scientific Research | Dimitrijevic M.S.,French National Center for Scientific Research | Dimitrijevic M.S.,Astronomical Observatory | Dimitrijevic M.S.,Institute Isaac Newton of Chile | Moreau N.,French National Center for Scientific Research
Journal of Physics: Conference Series | Year: 2012

Atomic physics in plasmas has been an essential tool for many years. Accurate spectroscopic diagnostics and modeling require the knowledge of numerous collisional line profiles. "Stark broadening" theories and calculations have been extensively developed for about 50 years. Nowadays, the access to such data via an on line database becomes essential. The aim of STARK-B is to reply to this need. It is a collaborative project between the Astronomical Observatory of Belgrade (AOB) and the "Laboratoire d'Étude du Rayonnement et de la matière en Astrophysique" (LERMA) of the Paris Observatory and CNRS. It is a database of widths and shifts of isolated lines of atoms and ions due to electron and ion impacts that we have calculated and published in international refereed journals (more than 150 papers by Dimitrijević & Sahal-Bréchot, and colleagues). It is devoted to modeling and spectroscopic diagnostics of stellar atmospheres and envelopes, laboratory plasmas, magnetic fusion plasmas, laser equipments and technological plasmas. Hence, the domain of temperatures and densities covered by the tables is wide and depends on the ionization degree of the considered ion. The STARK-B database is in free access and is is a part of VAMDC: the Virtual Atomic and Molecular Data Centre is an European Union funded collaboration between groups involved in the generation and use of atomic and molecular data. VAMDC aims to build a secure, documented, flexible and interoperable e-science environment-based interface to existing atomic and molecular data. STARK-B and its VAMDC context are presented in this paper.

Dimitrijevic M.S.,Astronomical Observatory | Dimitrijevic M.S.,Paris-Sorbonne University | Dimitrijevic M.S.,Institute Isaac Newton of Chile | Christova M.,Technical University of Sofia | And 3 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2016

Stark broadening parameters for 157 multiplets of helium-like boron (B iv) have been calculated using the impact semiclassical perturbation formalism. Obtained results have been used to investigate the regularities within spectral series. An example of the influence of Stark broadening on B iv lines in DO white dwarfs is given. © 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Milosavljevic V.,University of Belgrade | Milosavljevic V.,Dublin City University | Milosavljevic V.,Institute Isaac Newton of Chile | Simic Z.,Institute Isaac Newton of Chile | And 4 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2012

On the basis of 28 experimentally determined prominent neutral krypton (Kri) line shapes (in the 5s-5p and 5s-6p transitions), we have obtained electron (d e) and ion (d i) contributions to the total Stark shifts (d t). Stark shifts are also calculated using the semiclassical perturbation formalism (SCPF) for electrons, protons and helium ions as perturbers up to 50000K electron temperatures. Transition probabilities of spontaneous emission (Einstein's A k, i values) have been obtained using the relative line-intensity ratio method. The separate electron (d e) and ion (d i) contributions to the total Stark shifts are presented, as well as the ion-broadening parameters, which describe the influence of the ion-dynamical effect on the shift of the line shape, for neutral krypton spectral lines. We made a comparison of our measured and calculated d e data and compared both of these with other available experimental and theoretical d e values. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.

Cubarsi R.,Polytechnic University of Catalonia | Alcobe S.,Polytechnic University of Catalonia | Vidojevic S.,University of Belgrade | Vidojevic S.,University of Paris Descartes | And 3 more authors.
Astronomy and Astrophysics | Year: 2010

Discontinuities in the local velocity distribution associated with stellar populations are studied using the Maximum Entropy of the Mixture Probability from HIerarchical Segregation (MEMPHIS) improved statistical method, by combining a sampling parameter, an optimisation of the mixture approach, and a maximisation of the partition entropy for the constituent populations of the stellar sample. The sampling parameter is associated with isolating integrals of the stellar motion and is used to build a hierarchical family of subsamples. We provide an accurate characterisation of the entropy graph, in which a local maximum of entropy takes place simultaneously with a local minimum of the χ2 error. By analysing different sampling parameters, the method is applied to samples from the HIPPARCOS and Geneva-Copenhagen survey (GCS) to determine the kinematic parameters and the stellar population mixture of the thin disc, thick disc, and halo. The sampling parameter P = |(U, V,W)|, which is the absolute heliocentric velocity, allows us to build an optimal subsample containing both thin and thick disc stars, omitting most of the halo population. The sampling parameter P = |W|, which is absolute perpendicular velocity, allows us to create an optimal subsample of all disc and halo stars, although it does not allow an optimal differentiation of thin and thick discs. Other sampling parameters, such as P = |(U,W)| or P = |V|, are found to provide less information about the populations. By comparing both samples, HIPPARCOS provides more accurate estimates for the thick disc and halo, and GCS for the total disc. In particular, the radial velocity dispersion of the halo fits perfectly into the empirical Titius-Bode-like law σU = 6.6 (4/3) 3n+2, previously proposed for discrete kinematical components, where the values n = 0, 1, 2, 3 represent early-type stars, thin disc, thick disc, and halo populations, respectively. The kinematic parameters are used to segregate thin disc, thick disc, and halo stars, and to obtain a more accurate Bayesian estimation of the population fractions. To check the reliability of our results, an alternative segregation approach is used. GCS stars are classified into different kinematical populations in terms of their orbital parameters. The population fractions and velocity moments obtained by both methods are in excellent agreement. © 2010 ESO.

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