Stark broadening for Br VI and Kr V-VII lines in hot star atmospheres

International audienceContext. This paper provides missing Stark broadening of the Br VI and Kr V-VII lines recently discovered in the ultraviolet spectrum of the hot white dwarf RE 0503–289 and investigates the importance of the Stark broadening mechanism versus the Doppler mechanism in that star. As far as we know, this is the first time that Stark widths of Br VI and Kr V-VII lines have been calculated. Aims. The recent discovery of new lines of Br VI and Kr V-VII encourages us to provide their Stark broadening to enrich the STARK-B database and for use in interpretations of the observed spectra. Methods. We used our quantum mechanical method for calculating electron impact broadening to provide Stark widths. The method starts with an evaluation of the structure and collision parameters using the University College London codes SUPERSTRUCTURE/DISTORTED WAVE/JAJOM, which are adapted to the line broadening calculations. We then used the collision parameters to calculate the line widths using our programs. Results. We provide the missing widths of 35 lines of Br VI and Kr V-VII at different electron temperatures and at density N e = 10 17 cm −3 . We find that the Stark broadening mechanism is preponderant compared to the Doppler one for almost all the plasma conditions of the considered DO white dwarf atmospheres

Excitation cross-sections by electron impact for O V and O VI levels

International audienc

Checking the dependence on the upper level ionization potential of electron impact widths using quantum calculations

Using their dependence on the upper level ionization potential and the rest core charge of the emitter, electron impact line widths of several highly charged ions have been recently predicted. For most of them, neither theoretical nor experimental data are available (Mg VII, Na VII, Al VIII, Na VIII, Mg IX, Al X, Mg X, Al XI, Si XI, Ti XI, Cr XIII, Cr XIV, Fe XV, Fe XVI, Ni XVIII and Fe XXIII). The aim of this work is to check the above dependence and systematic trends of line widths by using quantum calculations. The comparison between the quantum results and the predicted ones shows that for the same element, the agreement is better for lower ionization degrees

Stark broadening and atomic data for Ar XVI

International audienceStark broadening and atomic data calculations have been developed for the recent years, especially atomic and line broadening data for highly ionized ions of argon. We present in this paper atomic data (such as energy levels, line strengths, oscillator strengths and radiative decay rates) for Ar XVI ion and quantum Stark broadening calculations for 10 Ar XVI lines. Radiative atomic data for this ion have been calculated using the University College London (UCL) codes (SUPERSTRUCTURE, DISTORTED WAVE, JAJOM) and have been compared with other results. Using our quantum mechanical method, our Stark broadening calculations for Ar XVI lines are performed at electron density Ne=1020 cm-3 and for electron temperature varying from 7.5 × 105 to 7.5 × 106 K. No Stark broadening results in the literature to compare with. So, our results come to fill this lack of data

Quantum Stark broadening of Ar XV lines. Strong collision and quadrupolar potential contributions

International audienc

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

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

Electron impact broadening of spectral lines in Be-like ions : quantum calculations

International audienc

Quantum mechanical line widths of ionized oxygen, silicon and aluminium; comparisons with recent experimental results

International audienceWe present in this paper new quantum Half Widths at Half intensity Maximum (HWHM) for 101 spectral lines of the following ions: O II (35 lines), O III (20 lines), Si II (9 lines), Si III (12 lines) and Al III (25 lines). The present quantum results are compared to new experimental ones. No previous quantum calculations have been performed for these ions. The relatively high differences found between the new and previous measurements and the available theoretical calculations encourage us to conduct these quantum calculations. Our quantum method has been used many years ago and has given good results compared to other approaches, so it can be a useful tool to check the new experimental results, or to understand the disagreement found for some lines. Furthermore, the obtained results can be used for the abundance determination of elements, the calculation of stellar opacity, the interpretation and modelling of stellar spectra, and the estimation of the relative transfer through stellar plasmas, etc. Part of the present results will be also implemented to the database of Stark broadening parameters STARK-B