ON THE STARK BROADENING OF Ar VII SPECTRAL LINES

Stark broadening parameters, full width at half maximum of s pectral line and shift, have been calculated for 3 spectral lines of Ar VII, for broadening by electron, proton, and He III impacts. For calculations, the semiclassical perturbation approach in the impact approximation has been used. The results are provided for temperatures from 20 000 K to 500 000 K and for an electron density of 10 17 cm -3 . Obtained results will be included in the STARK-B database which is also included in Virtual atomic and molecular data center (VAMDC).

Additionally, since for temperatures higher than around 10 000 K hydrogen is mainly ionized, Stark broadening is, in such a case, the principal pressure broadening mechanism (Griem, 1974).Consequently, in some at mospheric layers of A and late B stars, where such plasma conditions are typical, it should be taken into account.Such cases have been analysed for examp le in Simić et al. (2005b,a) and Simić et al. (2009).
Due to development of satellite-born spectroscopy, data on trace elements, which have been without significance for astrophysics, become more and mo re important for analysis of stellar spectra.It is also worth to notice that Rauch et al. (2007) accentuated that accurate Stark broadening data for as much as possible large number of atoms and ions and the corresponding spectral lines "are of crucial importance for sophisticated analysis of stellar spectra by means of NLTE model atmospheres".* Corresponding author: mdimitrijevic@aob.rsSpectral lines of Ar VII have been found by Taresch et al. (1997) in the spectrum of ext remely hot and massive galactic O3 If supergiant HD 93129A.Also Werner et al. (2007), by analyzing high-resolution spectra taken with the Far Ult raviolet Spectroscopic Exp lorer (FUSE), have identified Ar VII lines in some of the hotest known central stars of planetary nebulae, with the effective temperatures of 95000 -110000 K, and in (pre-) white dwarfs, where Stark broadening is very important and the corresponding Stark brooadening data are needed for a reliable analysis and modelling.
In order to provide the needed Stark broadening parameters for Ar VII spectral lines, completely missing in the existing literature, Stark Full Widths at Half intensity Maximu m (FWHM) W and shifts d for three transitions have been calculated by using semiclassical perturbation method (SCP, Sahal-Bréchot (1969a,b)) for co lissions of Ar VII ions with electrons, protons and He III ions, which are the main constituents of stellar at mospheres.
The Stark broadened profile F() of an isolated spectral line has Lorentzian form and can be represented as: Here,
In the upper equation E i and E f are energies of the initial and final states, while (W) and (d), in angular frequency units, are given by equation: with N is here denoted the electron density and with f(v) the Maxwellian velocity distribution function for electrons, ρ is the impact parameter of the incoming electron, and with i', f' are denoted the perturbing levels of the initial and final state.The inelastic cross section σ jj' (v), j = i, f is given with the formu la: where The phase shifts due to the polarization potential is φ p (r -4 ) and due to the quadrupolar potential φ q (r -3 ).They are defined in Section 3 o f Chapter 2 in Sahal-Bréchot (1969a).The cut-offs R 1 , R 2 , R 3 , and the Debye radius R D are described in Section 1 of Chapter 3 in Sahal-Bréchot (1969b).The contribution of Feshbach resonances, σ r is exp lained in details in (Fleurier et al.,1977).
All appro ximat ions and the details of the theory are discussed in detail in Sahal-Bréchot et al. (2014).The electrons are moving along hyperbolic paths while for ionic perturbers the paths are different because for them the Coulo mb force is repulsive and for them, in Eqs.(2-4), there is no the contribution of Feshbach resonances.

STARK B ROADENING PARAMET ER CALCULATIONS
Within the frame of se miclassical perturbation theory (Sahal-Bréchot, 1969a,b;Sahal-Bréchot et al., 2014) we have calculated using Eqs.(2-4) widths (FWHM) and shifts for three mu ltip lets of six t ime charged argon ion Ar VII.Energy levels necessary for present calculations have been taken from Salo man (2010).The needed oscillator strengths have been calculated within the Coulo mb approximation by using the method of Bates & Damgaard (1949) and the tables of Oertel & Shomo (1968).For higher levels, when there is no the corresponding data in Oertel & Shomo (1968), the required oscillator strengths have been calculated according to the article of Van Regemorter et al. (1979).
In Table 1, the obtained results of our calculations of Stark widths (FWHM) and shifts for electron-proton-and doubly charged heliu m ion-impact broadening, for a perturber density of 10 17 cm -3 and for a set of temperatures from 20 000 K to 500 000 K, are shown.The temperature range covers needs in astrophysics, laboratory plasma, fusion research, technology and the topic of lasers and laser produced plasma.Ext rapolation to perturber densities lower than 10 17 cm -3 is linear.For higher perturber densities the influence of Debye screening should be checked and eventualy taken into account (see e.g.(Griem, 1974)).W ith known Stark broadening parameters, W and d it is easy to obtain the line profile using Eq. ( 1).
One can see from Table 1, that spectral line width due to collisions with electrons is always dominant in co mparison with line widths produced by ionic collisions, since ions are much heavier than electrons and their velocities are much smaller.At low temperatures ion width is completely neglibig le but its influence increases with temperature and it should not be neglected at high temperatures.One can see as well that widths due to collisions with doubly charged heliu m ions are larger than widths produced by collisions with protons.Shifts are much smaller and they are of the same order of magnitude for collisions with electrons as well as with both species of ions.At higher temperatures ion shifts are larger than electron ones and proton shifts are smaller than He ++ ones.
It should be noticed that wavelengths given in Table 1 are calculated ones, so that they are different fro m experimental ones.However, they are correct in angular frequency units since then, for the calculation of Stark broadening parameters, relative and not absolute positions of energy levels are significant.In order to transform the Stark widths in Å-units to the width in angular frequency units the following formula can be used: where c is the speed of light.If the correction of widths and/or shifts for the difference between calculated and experimental wavelength is needed, this can be performed for the width as: Here, with W cor is denoted the corrected width, λ exp is the experimental, λ the calculated wavelength and W the width fro m Table 1.Fo rmulas for the shifts are analogous to Eqs. ( 5) and ( 6).
Parameter C (Dimit rijević & Sahal-Bréchot, 1984) in Table 1, enables to estimate the maximal perturber density fo r which the line may be treated as isolated, when it is divided by the corresponding full width at half maximu m.

ON THE IMPLEMENTATION OF RES ULTS IN THE STARK-B DATAB AS E
The presented in Table 1 Stark b roadening parameters for Ar VII spectral lines, will be also implemented in the STARK-B PHYSIC S database (Sahal-Bréchot et al., 2015, 2017), intended for the investigations, modelling and diagnostics of the plasma of stellar atmospheres, diagnostics of laboratory plasmas, and investigation of laser produced, inertial fusion plasma and for plasma technologies.
The STARK-B database contains Stark widths and shifts calculated by authors of this article and their coauthors, by using the SCP co mputer code for spectral lines, and published in more than 150 publications.Actually, in this database are SCP data for the following elements and ionization degrees: Table 1.This table gives electron-, proton-, and doubly charged helium-impact broadening parameters for Ar VII spectral lines, for a perturber density of 10 17 cm -3 and temperatures fro m 20 000 to 500 000 K. Calcu lated wavelength of the transitions (in Å) and parameter C are also given.This parameter, when divided with the corresponding Stark width, gives an estimate for the maximal pertuber density for which the line may be treated as isolated.W e : electron-impact full width at half maximu m of intensity, d e : electron-impact shift, W p : proton-impact fu ll width at half maximu m of intensity, d p : proton-impact shift, W He++ : doubly charged heliu m ion-impact full width at half maximu m of intensity, d He++ : doubly charged helium ion-impact shift.STARK-B contains also our Stark broadening data obtained by using the Modified SemiEmpirical method (MSE) (Dimitrijev ić & Konjević, 1980;Dimitrijević & Kršljanin, 1986;Dimit rijević & Popović, 2001).These data are of lower accuracy than SCP data but this approach is convenient for the cases where ato mic data are not sufficiently co mplete for an adequate SCP calculation.We note as well that STARK-B database is one of the databases which are in the Virtual Ato mic and Molecular Data Center -VAM DC (Dubernet et al., 2010;Rixon et al., 2011;Dubernet et al., 2016).VAM DC is created in order to enable an efficacious search and mining of ato mic and mo lecular data scattered in different databases and to make more convenient their adequate use.It has been the principal aim of a FP7 founded project of the same name (Dubernet et al., 2010), which started on July 1 2009 and lasted 42 months.During this project an interoperable e-infrastructure for ato mic and mo lecular data upgrading and integrating European (and wider) A&M database services has been build, and a foru m of data producers, data users and databases developers has been created.Currently in VAM DC are 30 databases with atomic and molecular data, including STA RK-B, and can be accessed and searched through VAM DC portal: http://portal.vamdc.org/.The web site of VAM DC Consortium is: http://www.vamdc.org/.

CONCLUS ION
We have performed a SCP calculat ion of Stark b roadening parameters for three mult iplets of Ar VII.Stark broadening parameters -widths and shifts, have been calculated for collisions of Ar VII ions with electrons, protons and doubly charged helium ions.The obtained data will be imp lemented in STARK-B database.There is no neither theoretical, nor experimental data for Stark broadening of Ar VII spectral lines and we hope that the obtained results will be of interest.for a number of problems in astrophysical, laboratory, laser produced, inertial fusion and technological plasmas.
Ag I, Al I, Al III, Al XI, Ar I, Ar II, Ar III, Ar VIII, Au I, B II, B III, Ba I, Ba II, Be I, Be II, Be III, Br I, C II, C III, C IV, C V, Ca I, Ca II, Ca V, Ca IX, Ca X, Cd I, Cd II, Cl I, Cl VII, Cr I, Cr II, Cu I, F I, F II, F III, F IV, F V, F VI, F VII, Fe II, Ga I, Ge I, Ge IV, He I, Hg II, I I, In II, In III, K I, K VIII, K IX, Kr I, Kr II, Kr VIII, Li I, Li II, Mg I, Mg II, Mg XI, Mn II, N I, N II, N III, N IV, N V, Na I, Na X, Ne I, Ne II, Ne III, Ne IV, Ne V, Ne VIII, Ni II, O I, O III, O IV, O V, O VI, O VII, P IV, P V, Pb IV, Pd I, Rb I, S III, S IV, S V, S VI, Sc III, Sc X, Sc XI, Se I, Si I, Si II, Si IV, Si V, Si VI, Si XI, Si XII, Si XIII, Sr I, Te I, Ti IV, Ti XII, Ti XIII, Tl III, V V, V XIII, Y III, Xe VI, Xe VIII and Zn I.
M SE Stark line widths, in some cases together with line shifts, of the following emitters are in STARK-B PHYSIC S database: Ag II, Al III, Al V, Ar II, Ar III, Ar IV, As II, Au II, B III, B IV, Be III, Bi II, Bi III, Br II, C III, C IV, C V, Cd II, Cd III, Cl III, Cl IV, Cl VI, Co II, Co III, Cu III, Cu IV, Eu II, Eu III, F III, F V, F VI, Fe II, Ga III, Ge III, Ge IV, I II, Kr II, Kr III, La II, La III, Lu III, Mg III, Mg IV, Mn II, Mn III, N II, N III, Na III, Na VI, Nb III, Ne III, Ne IV, Ne V, Ne VI, Ne VII, Ne VIII, O III, O IV, P III, P IV, P VI, Pt II, Ra II, S IV, Sb II, Sc II, Se II, Se III, Si IV, Si V, Si VI, Si XI, Sn III, Sr III, Ti II, Ti III, V II, V III, V IV, Xe II, Y II, Zn II, Zn III, Zr II and Zr III.