Semiclassical Perturbation Approach Research Articles

Stark broadening effect in hot DA white dwarfs: Ultraviolet lines of Fe V

AbstractStark widths and shifts have been calculated for 17 ultraviolet lines of Fe V of astrophysical interest. The calculations have been made using semiclassical perturbation approach. The work is motivated by the importance of ultraviolet lines for the study of hot white dwarf atmospheres specially for investigations of the variation of fine structure constant in strong gravitational field. Our Stark broadening parameters are presented for a range of temperature from 50,000 to 600,000 K. Our results are used to investigate the importance of electron impact broadening in plasma conditions of hot DA white dwarfs. Electron impact Stark width is compared to Doppler width as a function of atmospheric layer temperature and as a function of logarithm of Rosseland optical depth.

Stark broadening of Fe V spectral lines: 4s–4p transitions

ABSTRACT Using the impact semiclassical perturbation approach, widths and shifts of the 4s–4p configuration of Fe V spectral line profiles due to collisions with electrons, H+, He+, and He2 + ions, have been calculated in the physical conditions of hot white dwarfs. Energy levels and oscillator strengths needed for the calculation have been obtained by using the Hartree–Fock method with relativistic corrections. The results may be of interest not only for spectroscopic diagnostics in astrophysics, but also for laboratory plasmas, and technological plasmas. The obtained results will enter the STARK-B data base which is in free access and which is a node of the Virtual Atomic and Molecular Data Center – VAMDC.

Semiclassical perturbation Stark shifts of singly charged argon spectral lines

AbstractUsing semiclassical perturbation approach in impact approximation, Stark shifts for singly charged argon (Ar ii) spectral lines have been calculated. Energy levels and oscillator strengths needed for this calculation were determined using Hartree–Fock method with relativistic correction (HFR). We compare our results with experimental values for 100 spectral lines. We also present results as a function of temperature for 161 spectral lines for collisions with electrons, protons, singly charged helium and singly charged argon. This work extends our previous one.

Semiclassical Stark Broadening Parameters of Ar VII Spectral Lines

Using the semi-classical perturbation approach in the impact approximation, full width at half maximum and shift have been determined for eight spectral lines of Ar VII, for broadening by electron-, proton-, and He III-impacts. The results are provided for temperatures from 20,000 K to 500,000 K, and for an electron density of 10 18 cm − 3 . The obtained results will be included in the STARK-B database, which is also in the virtual atomic and molecular data center (VAMDC).

Stark Widths of Ar II Spectral Lines in the Atmospheres of Subdwarf B Stars

Stark broadening parameters are of interest for many problems in astrophysics and laboratory plasmas investigation. Ar II spectral lines are observed in many kinds of stellar atmospheres such as the atmospheres of B-Type stars and subdwarf B stars. In this work, we present theoretical Stark widths for Ar II spectral lines. We use the impact semiclassical perturbation approach. Our results are compared with the available experimental values. Finally, the importance of the Stark broadening mechanism is studied in atmospheric conditions of subdwarf B stars.

Stark Broadening in Compact Stars: Xe VI Lines

We will consider Stark broadening of non hydrogenic spectral lines in the impact approximation in compact stars: pre-white dwarf and white dwarf atmospheres. In order to show an example, Stark broadening parameters have been calculated, using the impact semiclassical perturbation approach for four Xe VI spectral lines. Obtained results have been used to demonstrate the influence of Stark broadening in DA and DB white dwarf atmospheres.

On the Application of Stark Broadening Data Determined with a Semiclassical Perturbation Approach

The significance of Stark broadening data for problems in astrophysics, physics, as well as for technological plasmas is discussed and applications of Stark broadening parameters calculated using a semiclassical perturbation method are analyzed.

Stark widths of Ar III spectral lines in the atmospheres of subdwarf B stars

Using semiclassical perturbation approach in impact approximation, we have calculated Stark widths for 32 spectral lines of doubly charged argon (Ar III). Oscillator strengths are calculated using Hartree–Fock method with relativistic correction (HFR) and an atomic model including 17 configurations. Energy levels are taken from NIST database. For perturbing levels for which the corresponding energy does not exist in NIST database, the calculated energies are used. Our widths are compared with the experimental results. The results presented here are of interest for modelling and investigation of stellar atmospheres since argon in different ionization stages is observed in many astrophysical objects. Finally, the importance of Stark broadening mechanism is studied in the atmospheric conditions of sdB stars. Electron impact Stark widths are compared to thermal Doppler widths as a function of temperature and optical depth of atmospheric layers.

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.

Stark-broadening calculations of singly ionized carbon spectral lines

Using the semiclassical perturbation approach in the impact approximation, we have obtained Stark-broadening parameters for 148 C ii multiplets. Energy levels and oscillator strengths are taken from the TOPbase data base. Results are obtained as a function of temperature for a set of 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. Thus, we have provided Stark-broadening data for the important charged perturbers in the atmospheres of carbon white dwarfs.

Ab Initio Determination of Atomic Structure and Stark Broadening Parameters: Pb IV and Recent Results

Abstract We present a review of our previous ab initio calculations of Stark broadening parameters using semi-classical perturbation method for the calculation of Stark widths and shifts, and the SUPERSTRUCURE (SST) code for the determination of atomic structure. SST code takes into account the configuration interactions and relativistic effects. New results are also presented for some spectral lines of Pb IV. Energy levels and oscillator strengths are calculated using Hartree-Fock relativistic approach, and the Stark broadening parameters are determined using a semiclassical perturbation approach.

Stark broadening of heavy metal spectral lines in atmospheres of chemically peculiar stars

Data on the Stark broadening of heavy metal spectral lines are of interest not only for laboratory but also for astrophysical plasma research as e.g. for stellar spectra analysis and synthesis. Here, we investigated theoretically the influence of collisions with charged particles on heavy metal spectral line profiles for Te I, Cr II, Mn II, Au II, Cu III, Zn III, Se III, In III and Sn III in spectra of A stars and white dwarfs. We applied semiclassical theory of Sahal-Bréchot since the most of published results in literature until now are determined using this method. When it can not be applied in an adequate way, due to the lack of reliable atomic data, we used modified semiempirical theory of Dimitrijević & Konjević, Dimitrijević & Kršljanin.Stark broadening parameters, widths and shifts, were obtained for spectral lines of neutral emitter Te I, singly charged emitters Cr II, Mn II and Au II and doubly charged emitters Cu III, Zn III, Se III, In III and Sn III. We considered as well the contributions of different collision processes to the total Stark width in comparison with Doppler one. In this case we obtained contributions for elastic, strong and inelastic collisions for upper and lower levels.For example, chromium lines are interesting due to their presence in stellar atmospheres, so that they give possibility to determine chromium abundance and investigate chromium stratification in stelar atmospheres and to be used for the diagnostics of stellar plasma and for more refined synthesis of stellar spectra. We consider the effect of Stark broadening on the shapes of Cr II spectral lines observed in the spectra of stars in the middle part of the main sequence. Stark broadening parameters were calculated by the semiclassical perturbation approach. For stellar spectra synthesis, the improved version SYNTH3 of the code SYNTH for synthetic spectrum calculations was used. Stark broadening parameters for Cr II spectral lines of seven multiplets belonging to 4s-4p transitions were calculated. New calculated Stark broadening parameters were applied to the analysis of Cr II line profiles observed in the spectrum of Cr-rich star HD 133792. We found that Stark broadening mechanism is very important and should be taken into account, especially in the study of Cr abundance stratification.

Stark broadening of visible Ar I spectral lines

Stark broadening parameters (width and shift) of six Ar I spectral lines: 522.1, 549.6, 518.6, 560.7, 603.2 and 696.5 nm, corresponding to the transitions 3p5nd →3p5 4p for n=7–5 and 4p′→4s have been calculated on the basis of the impact theory within the semi-classical perturbation approach. The case of the quasistatic ions has also been examined. The conditions of use of the presented results have been discussed. The considered lines are in the optical part of the spectrum and are of interest for laboratory research, particularly surface wave sustained discharges, and astrophysical purposes. The obtained results are compared with published experimental results and values calculated by other authors. The influence of the used coupling (j{\ ext-}L or LS) and oscillator strengths (The Opacity Project (TOP) database or Coulomb approximation) has also been considered.

The influence of Stark broadening on Cr II spectral line shapes in stellar atmospheres

Aims. We consider the effect of Stark broadening on the shapes of Cr ii spectral lines observed in stellar atmospheres of the middle part of the main sequence. Methods. Stark broadening parameters were calculated by the semiclassical perturbation approach. For stellar spectra synthesis, the improved version synth3 of the code synth for synthetic spectrum calculations was used. Results. Stark broadening parameters for Cr ii spectral lines of seven multiplets belonging to 4s − 4p transitions were calculated. New calculated Stark parameters were applied to the analysis of Cr ii line profiles observed in the spectrum of Cr-rich star HD 133792. Conclusions. We found that Stark broadening mechanism is very important and should be taken into account, especially in the study of Cr abundance stratification.

Stark broadening parameters for Cu III, Zn III and Se III lines in laboratory and stellar plasma

Using the modified semiempirical approach, we have considered Stark widths for 6 Cu III, 6 Zn III and 3 Se III transitions where the full semiclassical perturbation approach is not applicable in an adequate way due to the lack of reliable atomic data. Results are obtained as a function of temperature, for perturber density of 1017cm−3. Calculated results have been used to consider the influence of Stark broadening for A type star and DB white dwarf atmospheric conditions.

Electron impact broadening of multicharged ion lines of astrophysical interest: Ne VII, Ne VIII and Si XI

The modified semi-empirical method, often used in the investigations of stellar plasma for the determination of needed Stark line widths, is adapted here to use more accurate collision strengths instead of Gaunt factor. It is demonstrated that in such a way its applicability is extended to highly charged ions and good agreement is obtained with the more sophisticated semi-classical perturbation approach up to Si XI. Using this method, Stark line widths of several complex ions: two Be-like ions (Ne VII and Si XI) and one Li-like neon (Ne VIII) were calculated. The obtained results were compared with experiments and other theoretical approaches.

Influence of spectral line broadening on the mode structure of He-Kr and He-Ar gas lasers

Using the semiclassical perturbation approach, Stark broadening parameters for Kr II 469.4 nm, Ar II 476.5 nm, and Ar II 480.6 nm spectral lines have been determined. The obtained results have been used for the investigation of the role of the Stark broadening mechanism on the mode properties of hollow cathode excited noble gas mixture lasers. It has been found that for the He-KrII 469.4 nm laser broadening by neutral atom collisions is large enough to explain the single-mode operation of this laser, as opposed to the He-ArII 476.5 nm laser where Stark broadening also has to be taken into account to explain this property.

Stark Broadening of F III Lines in Laboratory and Stellar Plasma

Using a semiclassical approach, we have considered electron-, proton-, and ionized helium-impact line widths and shifts for the F III 2p34So-3s 4P resonant line. Moreover, for 10 F III multiplets where the full semiclassical perturbation approach is not applicable in an adequate way due to the lack of reliable atomic data, electron-impact line widths have been calculated within the modified semiempirical approach. Results are obtained as a function of temperature for perturber density of 1017 cm−3. The theoretical data obtained have been used to consider the influence of Stark broadening for A-type star atmosphere conditions.

Stark broadening of the four times ionized silicon spectral lines

Using a semiclassical perturbation approach, we have obtained Stark broadening parameters for 16 Si V multiplets using atomic data calculated ab initio with the SUPERSTRUCTURE code. In order to complete Stark broadening data for the most important charged perturbers in stellar atmospheres, Stark broadening parameters for proton-, He II-, and Si II-im- pact line widths and shifts are also presented. Results have been obtained for an electron density of 10 17 cm −3 as a function of temperature. Moreover, we have performed the same calculations with oscillator strengths calculated within the Coulomb approximation. The differences, which are within the error bars of the semiclassical perturbation approach (±20−30%) confirm that the Bates & Damgaard approximation may be used to complete the atomic data set needed for the Stark broadening calculations for multicharged ions like Si V, where more reliable oscillator strength values are not available.

Semi-Classical Calculations of Stark Broadening Impact Theory of Singly-Ionized Carbon, Nitrogen and Oxygen Spectral Lines

Using the semi-classical perturbation approach by Sahal-Bréchot (1969 Astron. Astrophys. 1, 91, 2 322; 1974 Astron. Astrophys. 35 321; 1991 Astron. Astrophys. 245 322) updated by Dimitrjević and Sahal-Bréchot (1984 J. Quant. Spectrosc. Radiat. Transf. 31 301; 1995 Physica Scripta 52 41) and by Ben Nessib et al. (1996 Physica Scripta 54 608) we have calculated Stark broadening widths of several C II, N II and O II spectral lines and input TOPbase (Opacity Project) sophisticated atomic structure data into the Sahal-Bréchot’s computer code. Then we have compared our results with those of available experiments and with Griem’s (1974) simplified semi-classical data. We show that our theoretical results, the simplified semi-classical calculations and experimental values are in good agreement. We also give new values of Stark broadening widths for several transitions of singly-ionized nitrogen and oxygen.