Nébil Ben Nessib

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

We present in this paper quantum mechanical calculations for the electron impact Stark linewidths of the 2s3s–2s3p transitions for the four beryllium-like ions from N IV to Ne VII. Calculations are made in the frame of the impact approximation and intermediate coupling, taking into account fine-structure effects. A comparison between our calculations, experimental and other theoretical results, shows a good agreement. This is the first time that such a good agreement is found between quantum and experimental linewidths of highly charged ions.

Quantum mechanical calculations of the electron-impact broadening of spectral lines for intermediate coupling

A new quantum mechanical expression for calculating electron-impact broadening is obtained for intermediate coupling. It would be especially useful for calculations of widths and shifts of fine structure spectral lines of multicharged ions where LS coupling breaks down.

Comparisons and Comments on Electron and Ion Impact Profiles of Spectral Lines

Abstract Stark broadening theory is currently operated for calculating widths and shifts of spectral lines that are needed for spectroscopic diagnostics and modeling in astrophysics, laboratory and technological plasmas. We have calculated a great number of data, obtained through the impact semiclassical perturbation theory: tables have been published for neutral atom and ion emitters, and typical temperatures, electron and ion densities. They are currently implemented in the STARK-B database which participates in the European effort within the Virtual Atomic and Molecular Data Centre. Despite of that, a great number of data are still missing. In the present paper, we revisit and compare a great number of the impact Stark widths and shifts by considering their semiclassical perturbation expressions. We also provide fitting formulae which are essential for the modeling codes of stellar atmospheres and envelopes.

Quantum calculations of Stark broadening of Li‐like ions; T and Z—scaling

Quantum‐mechanical calculations for the electron impact Stark linewidths of the 3s‐3p transitions for the lithium‐like ions from C IV to Ne VIII are performed in the frame of the impact approximation and for intermediate coupling. Good agreement is obtained with experimental and other theoretical results. Dependence of Stark widths with temperature and charge has been studied.

Quantum-mechanical Calculations of Ne VII Spectral Line Widths

We present in this paper quantum‐mechanical calculations for the electron impact Stark linewidths of the 2s3s–2s3p transitions for the beryllium‐like neon. Calculations are made in the frame of the impact approximation and for intermediate coupling, taking into account fine structure effects. A comparison between our calculations and experimental and other theoretical results showed a good agreement. This is the first time that we find such a good agreement between quantum and experimental linewidths of highly charged ions.

Electron-Impact Broadening of C II Spectral Lines

Using semiclassical perturbation approach in the impact approximation, we have obtained Stark broadening parameters for 149 C II multiplets. Energy levels and oscillator strengths are taken from the TOPbase database. Results are obtained as a function of temperature, for a perturber densities of 1014,1017 and 1018 cm−3. In addition to electron-impact full half widths and shifts, Stark broadening parameters due to singly ionized carbon-impacts have been calculated, in order to provide Stark broadening data for the important charged perturbers in the atmospheres of carbon white dwarfs. The complete results will be published elsewhere, as well as the comparison to the existing experimental and other theoretical data. As an example of obtained results, we present data for a part of multiplets with wavelengths in the visible part of the spectrum.

Cross Sections for Electron Impact Excitation of O VI Lines

Abstract Radiative atomic data and electron impact excitation cross sections for the 2s-2p transitions in O VI for transitions among the fine structure levels belonging to the 1s2nl (2 ≤ n ≤ 5) configurations have been calculated. We have extended the calculations of fine structure collision strengths up to 140 Ry and have compared our results at energies below 63 Ry to the R-matrix ones.

Semiclassical Stark broadening calculations of neutral oxygen lines

Using the semiclassical perturbation approach by Sahal-Brechot (1969, 1974, 1991) updated by Dimitrijevic and Sahal-Brechot (1984, 1995), we have calculated electronic and ionic widths and shifts of several OI spectral lines. The TOPbase (Opacity Project) atomic structure has been used. We have compared our results with those of available experiments and with Griem’s (1974) theoretical data.

Experimental and Theoretical Determination of Temperature in Plasmas

When plasma is in thermodynamic equilibrium, all species have the same kinetic temperature. In practice, plasmas are generally not in equilibrium, so different temperatures can be obtained. We investigated here temperature dependence of Stark widths for neutral atom spectral lines in order to find a more precise method for scaling with temperature.

Calculation of the Multiplet Factor (l1nl2ml3p) in LS‐coupling

Since the quadrupolar potential is predominant for a certain number of complex ions, the angular factors of the quadrupole term appearing in the semi‐classical expression of the width of line broadened by electron or ion perturbers is calculated in LS‐coupling for complex atoms, using the Fano‐Racah algebra. New diagonal multiplet factor formula for more complicated configuration as (l1n(LnSn)l2m(LmSm)l3p(LpSp) is provided.