Electron Impact Widths Research Articles

Theoretical study of electron-impact broadening for highly charged Ar XV ion lines

Spectral line widths produced by collisions between charged particles and emitters are of special interest for precise plasma spectroscopy. The highly charged Ar XV ion is demonstrated to have strong intrashell electron interactions, which manifest as an atomic system with many resonance structures, due to the quasi-degeneracy of orbital energies. In this paper we use the relativistic R-matrix method to investigate the electron-impact broadening of highly charged Ar XV ion spectral lines under the impact approximation. It is found that the results considering resonance structures are significantly different from those of the distorted wave approach. Furthermore, we propose a new empirical formula with a correction term to take into account the effect of resonances for electron-impact widths over a relatively wide range of plasma conditions. The corresponding fitting parameters of the new empirical formula for all 47 calculated transitions are also given with an estimated accuracy within 1%, which should be convenient for practical applications. The dataset that supported the findings of this study is available in Science Data Bank, with the link https://doi.org/10.57760/sciencedb.j00113.00101.

Stark broadening data for Si II multiplets within 3s3p([formula omitted]Po)nl configuration

The electron-impact widths for 13 Si II multiplets, belonging to the 3s3p(3Po)nl configuration, have been calculated by using the modified semiempirical method. Since a number of these lines is in visible, they are of interest and for analysis and synthesis of stellar Si II lines, abundance determination and modelling of stellar atmospheres.The obtained results have been compared with available experimental and theoretical data and used for the investigation of regularities within supermultiplets.

Virtual Laboratory Astrophysics and the STARK-B database VAMDC node: a resource for electron and ion impact widths and shifts of isolated lines

SynopsisStark broadening theories and calculations can now be considered as mature. The fast computers allow to calculate a great number of atomic data needed for accurate spectroscopic diagnostics and modeling, such as for stellar atmospheres and envelopes, laboratory and technological plasmas, and laser equipments. Thus the access to these data via an on line database is essential. The STARK-B database is intended to meet this need. It contains calculated widths and shifts of isolated atomic lines due to electron and ion impacts. It is still under development and will be presented at the Conference.

Stark shift of the CI 2479 Å spectral line of carbon

The Stark shift of the CI 2479 A emission line of atomic carbon is measured in a broad range of electron densities between ~6 × 1016 and ~4 × 1018 cm–3. It is established that the shift is linear and its value is significantly lower than that predicted by theory. The line shape is found to be dominated by the Stark effect at Т = 32 kK and electron concentration N e ≈ 3.9 × 1018 cm–3. The electron-impact and ion widths of this contour are in good agreement with the Grim data, while its total shift to longer wavelengths is found to be half that calculated theoretically.

A Brief Overview about Laser-Ablated Molybdenum Plasma Properties

First step in molybdenum isotope separation for medical purposes project, based in laser ablation followed by electromagnetic separation methods, is the characterization of ablated plasma plume. In this work, a depth profile emission spectroscopy study of laser-ablated molybdenum plasma expanding on air at atmospheric pressure was performed, considering Local Thermodynamic Equilibrium and one-dimensional uniform expanding models. Plasma temperature, electron density, electron population distribution and electron impact width parameter were evaluated along plasma expansion axis and reach average values of 15000 K,1018cm-3, 1% of electron populationat 4d45s6sstate and (0.017±0.008) nm, respectively. Furthermore, mean velocity of (5.0±0.7) km/sand the plasma lifetime that was (160± 14)ns for length equal to (1.80±0.05) mm weremeasured. So, this work includes a description of mainly plasma plume parameters, which permits a discussion for isotope separation methods related to laser ablation.

Experimental Stark parameters of Mn I lines in the y6P° → a 6 S multiplet under conditions of “long” laser plasma

The Stark broadening parameters for the components of the y6P° → a 6 S Mn I multiplet have been determined under conditions of “long” laser plasma: the electron impact width and line shift due to the quadratic Stark effect have been measured in the range of electron densities of (4.8–45) × 1016 cm–3. The presence of positive Stark shifts of the multiplet components (from +0.1 to +0.15 A) has been demonstrated for the first time. The Stark widths are found to increase in the multiplet with a decrease in J of the upper level and significantly decrease with an increase in the plasma temperature. The d/w ratio is identical for all multiplet components; it amounts to 0.35–0.65, depending on the observation conditions. The dependences of this ratio on the plasma temperature and electron density have also been considered.

Molybdenum electron impact width parameter measurement by laser-induced breakdown spectroscopy

In this work, we suggest a method for electron impact width parameter calculation based on Stark broadening of emission lines of a laser-ablated plasma plume. First, electron density and temperature must be evaluated by means of the Saha–Boltzmann plot method for neutral and ionized species of the plasma. The method was applied for laser-ablated molybdenum plasma plume. For molybdenum plasma electron temperature, which varies around 10,000 K, and electron density, which reaches values around 1018 cm−3, and considering that total measured line broadening was due experimental and Stark broadening mainly, electron impact width parameter of molybdenum emission lines was determined as (0.01 ± 0.02) nm. Intending to validate the presented method, it was analyzed the laser-ablated aluminum plasma plume and the obtained results were in agreement with the predicted on the literature.

On the Stark Broadening of Lu III Spectral Lines

The electron-impact widths for 27 Lu III spectral lines have been calculated by using the modified semiempirical method. Calculations have been also performed with the published relativistic Hartree-Fock oscillator strengths and additionally, with the approximate formula of Cowley. With the obtained results, the influence of Stark broadening on Lu III lines was investigated in the spectra of A-type stars. The obtained data will be included in the STARK-B database, which is part of the Virtual Atomic and Molecular Data Center – VAMDC.

Electron-Impact Widths and Shifts of B III 2p-2s Lines

In this paper, we present results for the relativistic quantum mechanical calculations of electron-impact line widths and shifts of 2p-2s transitions in doubly ionized boron (B III) ions. We use the Dirac R-matrix methods to solve (N + 1)-electron colliding systems for the scattering matrices that are required. The line widths are calculated for an electron density 1:81 × 1018 cm-3 and electron temperature 10:6 eV. The obtained results agree well with all the semiempirical calculations and most of the semiclassical calculations, and are closer to the experimental results published by Glenzer and Kunze (Glenzer, S.; Kunze, H.-J. Stark broadening of resonance transitions in B III. Phys. Rev. A 1996, 53, 2225–2229). Our line widths are almost twice as large as the earlier quantum mechanical calculations for the set of particular plasma conditions.

Stark broadening data for spectral lines of rare-earth elements: Nb III

The electron-impact widths for 15 doubly charged Nb ion lines have been theoretically determined by using the modified semiempirical method. Using the obtained results, we considered the influence of the electron-impact mechanism on line shapes in spectra of chemically peculiar stars and white dwarfs.

A new approach to determination of the asymmetry parameter of Stark-broadened isolated spectral lines

A new approach to evaluation of asymmetry parameters of Stark-broadened isolated spectral lines is presented. The procedure is discussed on the example of the N I line at λ = 9822.75 A. Line shape measurements were performed using a wall-stabilized arc, operated at atmospheric pressure. The radiation of the plasma, emitted from homogeneous plasma layers in end-on direction, was measured using a grating spectrometer equipped with a two-dimensional CCD detector. Griem-like profiles, convoluted with the corresponding Doppler and apparatus profiles, were fitted to experimental data. In this way the Stark broadening parameters (electron impact widths, shifts and asymmetry) have been determined. Detailed analysis of the line shapes shows that the standard Griem-like profile does not explain the observed line asymmetry satisfactorily. The results of preliminary studies indicate that including collision-duration effects in profile calculations provides a better agreement between experiment and calculations. PACS. 32.70.Jz Line shapes, width, and shift – 52.70.Kz Optical (ultraviolet, visible, infrared) measurements.

Electron-impact widths and shifts of SrII lines in ultracold neutral plasmas

In this paper, we report on relativistic quantum-mechanical calculations of electron-impact linewidths and line shifts in singly ionized strontium ions in ultracold neutral plasmas. We have used the Dirac $R$-matrix methods to solve ($N+1$)-electron colliding systems and to generate the required scattering matrices. Calculated linewidths and line shifts at an electron density ${10}^{17}\phantom{\rule{0.16em}{0ex}}{\text{cm}}^{\ensuremath{-}3}$ and electron temperatures (several electronvolts) agree well with other theoretical calculations and are closer to the experimental observations. Our theoretical findings of linewidths and line shifts are almost twice as large as the earlier calculations for the particular selected plasma conditions. This work develops these quantum-mechanical procedures and applies them to the emission from ultracold neutral plasmas.

Electron impact broadening of Si IV spectral lines: Comparison with recent experiments

Electron impact widths of eight Si IV spectral lines have been calculated using our quantum mechanical method. Semiclassical perturbation calculations using atomic data from the SUPERSTRUCTURE code have been also performed. Comparison with recent measurements shows that they are always lower than our quantum mechanical, semiclassical perturbation and all other theoretical results. A disagreement in the importance of fine structure effects between our results and the measured ones has been reported here.

Quantum Stark broadening data for the C iv, N v, O vi, F vii and Ne viii resonance doublets

In this paper, we present new Stark electron impact widths of the 2s–2p resonance doublets of the C IV ,N V ,O VI ,F VII and Ne VIII ions, obtained using our quantum mechanical method. The present results are required to develop future spectral analysis using non-local thermodynamic equilibrium model atmospheres, which can make the determination of photospheric properties more accurate. Results are presented for a large range of electron temperatures required for plasma modelling. These are compared to the available theoretical ones. They are also used to check the previously obtained semiclassical perturbation results, and very good agreement is found. The atomic structure and collision data, used for the calculations of line broadening for the five ions studied here, are also calculated and compared to available theoretical results. The agreement found between the two calculations ensures that our line-broadening procedure uses the adequate structure and collision data. Scalings of linewidths with effective charge Z are also studied.

Experimental stark parameters of carbon C II 2993 Å line

Total Stark profiles of the C II 2993 A line of a plasma jet of a slit discharge with an evaporating wall. In the interval of electron densities of 1017 to 6 × 1017 cm−3, the electron impact width, the ionic broadening and the shift of the intensity maximum of the line are measured. It is found that, at an inversely quadratic dependence of the electron impact width on the electron concentration, the Stark shift and the ionic contribution to the total width of the profile are linear. It is noted that calculated values of the shift regularly exceed measured values, while the signs of the measured and calculated shifts coincide. The method of approximating experimental data is proposed, which takes into account the interrelation of the main Stark parameters in plasma with a strong interparticle interactions.

Stark broadening studies of the infrared OI multiplet

Experimental line broadening studies of the infrared OI multiplet are reported. Stark broadening parameters, electron-impact widths (w) and shifts (d) as well as asymmetry (A), are determined applying a wall-stabilized high-current arc as the plasma source. Broadening studies are performed in the electron density range 0.8 × 1016–1.4 × 1016 , corresponding to plasma temperatures from 12 000 to 13 800 K. The obtained broadening and shift parameters, normalized to the standard electron density value of 1 × 1016 , are compared with results of calculations reported in a 1974 monograph by Griem.

Electron density of an individual microdischarge channel in patterns in a dielectric barrier discharge at atmospheric pressure

The electron density of an individual microdischarge channel in different stable patterns including a square and a hexagon pattern in a dielectric barrier discharge in argon at atmospheric pressure is investigated using a spectral line profile method. The procedure for deconvolution of the asymmetric convolution integral is used to obtain the Stark broadening and shift of Ar I 696.54 nm for the calculation of electron density. The broadening parameters such as electron impact width ωe and ion impact width α can also be obtained from the procedure. By comparing ωe with the theoretical values at different electron temperatures given by Griem, the electron temperature can be reasonably estimated. It is found that the electron density in an individual microdischarge channel increases with increasing voltage.

On simultaneous determination of electron impact width, ion-broadening and ion-dynamic parameter from the shape of plasma broadened non-hydrogenic atom line

Recently, experimental electron impact widths and ion broadening parameters of isolated Kr I lines were reported. In addition, the contribution of Kr II and Kr III ion dynamics to Kr I line widths is determined. Here, on the basis of the critical evaluation of the plasma source, the deconvolution procedure and earlier results by the same authors, possible causes for erroneous line shape recordings and their interpretation, are discussed. To demonstrate the experimental difficulties in the procedure used for Stark broadening parameter measurements, an additional experiment is performed and profiles of plasma-broadened lines are generated. All our new results and the analysis of the plasma source, experimental procedure and reported data of Kr I lines indicate that certain aspects of earlier work need further investigation.

Electron broadening of isolated lines with stationary non-equilibrium level populations

It is shown that a quantum kinetic theory approach to line broadening, extended to stationary non-equilibrium states, yields corrections to the standard electron impact widths of isolated lines that depend on the population of the radiator internal levels. A consistent classical limit from a general quantum treatment of the perturbing electrons also introduces corrections to the isolated line widths. Both effects are essential in preserving detailed-balance relations. Preliminary analysis indicates that these corrections may resolve existing discrepancies between theoretical and experimental widths of isolated lines. An experimental test of the results is proposed.

Stark broadening and shift measurements of two doubly excited NI multiplets

Experimental Stark-broadening studies of two selected doubly excited NI multiplets from the infrared wavelength range are presented. One of them is very sensitive to interactions with charged particles in plasmas and the other exhibits — at the same plasma conditions — only very small broadening and shift. A high current wall-stabilized arc operated in helium with admixture of nitrogen and hydrogen was applied as the excitation source. The radiation of the plasma was detected by applying a grating spectrometer equipped with a CCD detector. Measurements were performed at electron densities of the plasma between 3×1015 and 7×1015 cm-3, corresponding to temperatures from the range 8000–10500 K. Electron impact widths (we) and shifts (de) of fine structure components of these multiplets were determined. The evaluated Stark broadening parameters (we, de) are compared with other experimental data and with calculated Stark effect constants.