Haykel Elabidi

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.

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

Abstract We present in this paper electron impact broadening for six Ar XV lines using our quantum mechanical formalism and the semiclassical perturbation one. Additionally, our calculations of the corresponding atomic structure data (energy levels and oscillator strengths) and collision strengths are given as well. The lines considered here are divided into two sets: a first set of four lines involving the ground level: 1s 2 2s 2 1 S 0 – 1s 2 2s n p 1 P 1 o where 2 ⩽ n ⩽ 5 and a second set of two lines involving excited levels: 1s 2 2s2p 1 P 1 o –1s 2 2s3s 1 S 0 and 1s 2 2s2p 3 P 0 o –1s 2 2s3s 3 S 1 . An extensive comparison between the quantum and the semiclassical results was performed in order to analyze the reason for differences between quantum and semiclassical results up to the factor of two. It has been shown that the difference between the two results may be due to the evaluation of strong collision contributions by the semiclassical formalism. Except few semiclassical results, the present results are the first to be published. After the recent discovery of the far UV lines of Ar VII in the spectra of very hot central stars of planetary nebulae and white dwarfs, the present -and may be further- results can be used also for the corresponding future spectral analysis.

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.

Structural and collisional data for Mg III and Al IV

We present in this work energy levels, oscillator strengths, radiative decay rates and fine structure collision strengths for the Mg III and Al IV ions. The 11 configurations: (1s2) 2s22p6, 2s22p53l, 2s2p63l, 2s22p54l (l⩽n-1, where n is the principal quantum number), yielding the lowest 75 levels are used. The collisional data for these two ions are missing in the literature, especially the database CHIANTI, this is the principal motivation behind the present work. Calculations have been performed using the AUTOSTRUCTURE code. AUTOSTRUCTURE treats the scattering problem in the distorted wave approach. Fine structure collision strengths are calculated for a range of electron energies from 10 Ry to 240 Ry. The atomic structure data are compared to available experimental and theoretical results.

Electron impact excitation for Ar VI

Radiative atomic and electron impact excitation data for Ar VI ion have been calculated using the AUTOSTRUCTURE code. The two-body non-fine structure operators of the Breit-Pauli Hamiltonian have been incorporated in AUTOSTRUCTURE, and for the collisional problem, we use the distorted wave approximation. We compare our radiative atomic results with the few available ones. To our best knowledge, there are no distorted wave collision strengths for Ar VI. Some discrepancies have been reported between our oscillator strengths and the only calculated ones using the MCHF method. We perform the same calculations with the UCL codes SST/DW/JAJOM and we compare with the present AUTOSTRUCTURE results.

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.