scholarly journals Monopole Contribution to the Stark Width of Hydrogenlike Spectral Lines in Plasmas: Analytical Results

Plasma ◽  
2020 ◽  
Vol 3 (4) ◽  
pp. 180-186
Author(s):  
Eugene Oks

One of the most reliable and frequently used methods for diagnosing various laboratory and astrophysical plasmas is based on the Stark broadening of spectral lines. It allows for determining from the experimental line profiles important parameters, such as the electron density and temperature, the ion density, the magnetic field, and the field strength of various types of the electrostatic plasma turbulence. Since, in this method, radiating atoms or ions are used as the sensitive probes of the above parameters, these probes have to be properly calibrated. In other words, an accurate theory of the Stark broadening of spectral lines in plasmas is required. In the present paper, we study, analytically, the monopole contribution to the Stark width of hydrogen-like spectral lines in plasmas. For this purpose, we use the formalism from paper by Mejri, Nguyen, and Ben Lakhdar. We show that the monopole contribution to the width has a non-monotonic dependence on the velocity of perturbing electrons. Namely, at relatively small electron velocities, the width decreases as the velocity increases. Then it reaches a minimum and (at relatively large electron velocities), as the velocity further increases, the width increases. The non-monotonic dependence of the monopole contribution to the width on the electron velocity is a counter-intuitive result. The outcome that at relatively large electron velocities, the monopole contribution to the width increases with the increase in the electron velocity is in a striking distinction to the dipole contribution to the width, which decreases as the electron velocity increases. We show that, in the situation encountered in various areas of plasma research (such as in magnetically-controlled fusion), where there is a relativistic electron beam (REB) in a plasma, the monopole contribution to the width due to the REB exceeds the corresponding dipole contribution by four orders of magnitude and practically determines the entire Stark width of hydrogenic spectral lines due to the REB.

2012 ◽  
Vol 29 (1) ◽  
pp. 20-28 ◽  
Author(s):  
I. Tapalaga ◽  
I. P. Dojčinović ◽  
M. K. Milosavljević ◽  
J. Purić

AbstractDependences of electron and proton impact Stark width on the upper level ionization potential within different series of the neutral calcium spectral lines have been evaluated and discussed. The similar dependences previously found for the electron impact contribution were also obtained for the proton impact contribution to the Stark broadening. The emphasis is on the term structure influence on the studied Stark width dependences. The influence of the lower transition level and transition term is higher at low temperatures. After establishing these dependences, predictions were made for Stark widths of neutral calcium spectral lines not measured experimentally or calculated theoretically until now.


Data ◽  
2020 ◽  
Vol 5 (4) ◽  
pp. 106
Author(s):  
Milan S. Dimitrijević ◽  
Magdalena Christova ◽  
Sylvie Sahal-Bréchot

Calculated Stark broadening parameters of singly ionized beryllium spectral lines have been reported. Three spectral series have been studied within semiclassical perturbation theory. The plasma conditions cover temperatures from 2500 to 50,000 K and perturber densities 1011 cm−3 and 1013 cm−3. The influence of the temperature and the role of the perturbers (electrons, protons and He+ ions) on the Stark width and shift have been discussed. Results could be useful for plasma diagnostics in astrophysics, laboratory, and industrial plasmas.


2020 ◽  
Vol 496 (4) ◽  
pp. 5584-5590 ◽  
Author(s):  
Zlatko Majlinger ◽  
Milan S Dimitrijević ◽  
Vladimir A Srećković

ABSTRACT Stark full widths at half-maximum for 46 Co ii multiplets have been calculated using modified semi-empirical method. The obtained results have been used to demonstrate the importance of Stark broadening mechanism in DA and DB white dwarf and A star atmospheres. With the obtained results we also test possibility of using some approximate methods of Stark width calculations developed on the basis of regularities and systematic trends.


2021 ◽  
Vol 923 (2) ◽  
pp. 207
Author(s):  
Melania Cubas Armas ◽  
Damian Fabbian

Abstract We compare results of simulations of solar facular-like conditions performed using the numerical codes MURaM and STAGGER. Both simulation sets have a similar setup, including the initial condition of ≈200 G vertical magnetic flux. After interpolating the output physical quantities to constant optical depth, we compare them and test them against inversion results from solar observations. From the snapshots, we compute the monochromatic continuum in the visible and infrared, and the full Stokes vector of the Fe i spectral line pair around 6301–6302 Å. We compare the predicted spectral lines (at the simulation resolution and after smearing to the HINODE SP/SOT resolution) in terms of their main parameters for the Stokes I line profiles, and of their area and amplitude asymmetry for the Stokes V profiles. The codes produce magnetoconvection with similar appearance and distribution in temperature and velocity. The results also closely match the values from recent relevant solar observations. Although the overall distribution of the magnetic field is similar in both radiation-magnetohydrodynamic (RMHD) simulation sets, a detailed analysis reveals substantial disagreement in the field orientation, which we attribute to the differing boundary conditions. The resulting differences in the synthetic spectra disappear after spatial smearing to the resolution of the observations. We conclude that the two sets of simulations provide robust models of solar faculae. Nevertheless, we also find differences that call for caution when using results from RMHD simulations to interpret solar observational data.


2011 ◽  
Vol 28 (4) ◽  
pp. 281-289 ◽  
Author(s):  
I. P. Dojčinović ◽  
I. Tapalaga ◽  
J. Purić

AbstractThe dependences of Stark width on the upper-level ionization potential within different series of the neutral beryllium spectral lines have been studied. The dependences previously observed for electron impact contribution to the Stark widths were also obtained for the proton impact contribution. The emphasis is on the fine structure influence on the studied Stark parameter dependences. The influence of temperature on the dependences of Stark width parameters has been demonstrated. The relations found can be used in both cases for prediction of new Stark broadening data, thus avoiding much more complicated procedures.


1988 ◽  
Vol 6 (2) ◽  
pp. 377-383 ◽  
Author(s):  
B. V. Ljublin ◽  
V. Yu. Yasevich ◽  
D. G. Yakovlev

Stark broadening of Lyman lines in high density plasmas is treated theoretically to study the effects of the fields inside the plasmas, the microfield, and the oscillating fields from Langmuir waves. Resonance features are expected to be observed from the line profiles, especially about the microfield.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Milan S. Dimitrijević

Stark broadening parameters, full widths at half maximum (FWHM) and shifts for spectral lines within six multiplets of doubly charged ruthenium ions have been calculated, for an electron density of 1017 cm-3 and temperature range from 10 000 K to 160 000 K. Calculations have been performed with the simplified modified semiempirical (SMSE) approach. In the case of two multiplets, it is possible to apply the full modified semiempirical method. The corresponding calculations have been performed and results are compared in order to test and determine the accuracy of the SMSE approach. The results are also used for the consideration of Stark width and shift regularities in Ru III spectrum.


1977 ◽  
Vol 36 ◽  
pp. 191-215
Author(s):  
G.B. Rybicki

Observations of the shapes and intensities of spectral lines provide a bounty of information about the outer layers of the sun. In order to utilize this information, however, one is faced with a seemingly monumental task. The sun’s chromosphere and corona are extremely complex, and the underlying physical phenomena are far from being understood. Velocity fields, magnetic fields, Inhomogeneous structure, hydromagnetic phenomena – these are some of the complications that must be faced. Other uncertainties involve the atomic physics upon which all of the deductions depend.


2019 ◽  
Vol 15 (S356) ◽  
pp. 94-94
Author(s):  
Marco Berton

AbstractLine profiles can provide fundamental information on the physics of active galactic nuclei (AGN). In the case of narrow-line Seyfert 1 galaxies (NLS1s) this is of particular importance since past studies revealed how their permitted line profiles are well reproduced by a Lorentzian function instead of a Gaussian. This has been explained with different properties of the broad-line region (BLR), which may present more pronounced turbulent motions in NLS1s with respect to other AGN. We investigated the line profiles in a recent large NLS1 sample classified using SDSS, and we divided the sources into two subsamples according to their line shapes, Gaussian or Lorentzian. The line profiles seem to separate all the properties of NLS1s. Black hole mass, Eddington ratio, [OIII] luminosity, and Fe II strength are all very different in the Lorentzian and Gaussian samples, as well as their position on the quasar main sequence. We interpret this in terms of evolution within the class of NLS1s. The Lorentzian sources may be the youngest objects, while Gaussian profiles may be typically associated to more evolved objects. Further detailed spectroscopic studies are needed to fully confirm our hypothesis.


Atoms ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 29
Author(s):  
Sylvie Sahal-Bréchot

The present paper revisits the determination of the semi-classical limit of the Feshbach resonances which play a role in electron impact broadening (the so-called “Stark“ broadening) of isolated spectral lines of ionized atoms. The Gailitis approximation will be used. A few examples of results will be provided, showing the importance of the role of the Feshbach resonances.


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