232 research outputs found
Stark broadening of B IV spectral lines
Stark broadening parameters for 157 multiplets of helium like boron (B IV)
have been calculated using the impact semiclassical perturbation formalism.
Obtained results have been used to investigate the regularities within spectral
series. An example of the influence of Stark broadening on B IV lines in DO
white dwarfs is given.Comment: 6 pages, 2 figure
Stark broadening of B IV lines for astrophysical and laboratory plasma research
Stark broadening parameters for 36 multiplets of B IV have been calculated
using the semi-classical perturbation formalism. Obtained results have been
used to investigate the regularities within spectral series and temperature
dependence.Comment: 8 pages, 6 figures, 1 table, in press in Advances in Space Researc
On the influence of Stark broadening on Si I lines in stellar atmospheres
We study the influence of Stark broadening and stratification effects on Si\i
lines in the rapidly oscillating (roAp) star 10 Aql, where the Si\i 6142.48 \AA
and 6155.13 \AA lines are asymmetrical and shifted. First we have calculated
Stark broadening parameters using the semiclassical perturbation method for
three Si\i lines: 5950.2 \AA, 6142.48 \AA and 6155.13 \AA. We revised the
synthetic sp$ calculation code taking into account both Stark width and shift
for these lines. From the comparison of our calculations with the observations
we found that Stark broadening + the stratification effect can explain
asymmetry of the Si\i 6142.48 \AA and 6155.13 \AA lines in the atmospere of
roAp star 10 Aql.Comment: Accepted to A&
The OIV 1407.3\AA /1401.1\AA\ emission-line ratio in a plasma
Line ratio of O IV 1407.3 \AA/1401.1 \AA\- is calculated using mostly our own
atomic and collisional data. Energy levels and oscillator strengths needed for
this calculation have been calculated using a Hartree-Fock relativistic (HFR)
approach. The electron collision strengths introduced in the statistic
equilibrium equations are fitted by polynomials for different energies.
Comparison has also been made with available theoretical results. The provided
line ratio has been obtained for a set of electron densities from
cm to cm and for a fixed temperature of 50 000 K.Comment: 6 pages, 1 figure, 2 tables. Accepted for publication in Advances in
Space Researc
Hydrogen H line polarization in solar flares. Theoretical investigation of atomic polarization by proton beams considering self-consistent NLTE polarized radiative transfer
Context. We present a theoretical review of the effect of impact polarization
of a hydrogen H line due to an expected proton beam bombardment in
solar flares. Aims. Several observations indicate the presence of the linear
polarization of the hydrogen H line observed near the solar limb above
5% and preferentially in the radial direction. We theoretically review the
problem of deceleration of the beam originating in the coronal reconnection
site due to its interaction with the chromospheric plasma, and describe the
formalism of the density matrix used in our description of the atomic processes
and the treatment of collisional rates. Methods. We solve the self-consistent
NLTE radiation transfer problem for the particular semiempirical chromosphere
models for both intensity and linear polarization components of the radiation
field. Results. In contrast to recent calculations, our results show that the
energy distribution of the proton beam at H formation levels and
depolarizing collisions by background electrons and protons cause a significant
reduction of the effect below 0.1%. The radiation transfer solution shows that
tangential resonance-scattering polarization dominates over the impact
polarization effect in all considered models. Conclusions. In the models
studied, proton beams are unlikely to be a satisfying explanation for the
observed linear polarization of the H line.Comment: 11 pages, 11 figures, accepted for publication in A&
On the influence of Stark broadening on Cr I lines in stellar atmospheres
Using the semiclassical perturbation method, electron-, proton-, and ionized
helium-impact line widths and shifts for the nine Cr I spectral lines from the
multiplet, have been calculated for a perturbers density of
10 cm and temperatures T =2,500 - 50,000 K. The obtained results
have been used to investigate the influence of Stark broadening effect in the
Cr-rich Ap star CrB atmosphere on line shapes of these lines. It has
been found that the contribution of the proton and He II collisions to the line
width and shift is significant, and it is comparable and sometimes (depending
of the electron temperature) even larger than electron-impact contribution.
Moreover, not only the Stark line width, but, depending on the electron-,
proton-, and He\ii density in stellar atmosphere also the Stark shift may
contribute to the blue as well as to the red asymmetry of the same line. The
obtained results have been used to investigate the influence of Stark
broadening effect on line shapes of Cr\i lines in the atmosphere of Cr-rich Ap
star CrB.Comment: 8 pages, Astron. Astrophys. accepte
The STARK-B database as a resource for \textquotedblleft STARK" widths and shifts data: State of advancement and program of development
\textquotedblleft Stark" broadening theories and calculations have been
extensively developed for about 50 years and can now be applied to many needs,
especially for accurate spectroscopic diagnostics and modeling. This requires
the knowledge of numerous collisional line profiles. Nowadays, the access to
such data via an online database becomes essential. STARK-B is a collaborative
project between the Astronomical Observatory of Belgrade and the Laboratoire
d'\'Etude du Rayonnement et de la mati\`ere en Astrophysique (LERMA). It is a
database of calculated widths and shifts of isolated lines of atoms and ions
due to electron and ion collisions (impacts). It is devoted to modeling and
spectroscopic diagnostics of stellar atmospheres and envelopes, laboratory
plasmas, laser equipments and technological plasmas. Hence, the domain of
temperatures and densities covered by the tables is wide and depends on the
ionization degree of the considered ion. STARK-B has been fully opened since
September 2008 and is in free access.
The first stage of development was ended in autumn 2012, since all the
existing data calculated with the impact semiclassical-perturbation method and
code by Sahal-Br\'echot, Dimitrijevi\'c and coworkers have now been
implemented. We are now beginning the second stage of the development of
STARK-B. The state of advancement of the database and our program of
development are presented here, together with its context within VAMDC. VAMDC
(Virtual Atomic and Molecular Data Center) is an international consortium which
has built a secure, documented, flexible interoperable platform e-science
permitting an automated exchange of atomic and molecular data.Comment: 4 pages, in press in Advances in Space Researc
Stark Broadening in Compact Stars: Xe VI Lines
International audienceWe 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
Atomic data and electron-impact broadening effect in DO white dwarf atmospheres: Si VI
Energy levels, electric dipole transition probabilities and oscillator
strengths in five times ionized silicon have been calculated in intermediate
coupling. The present calculations were carried out with the general purpose
atomic-structure program SUPERSTRUCTURE. The relativistic corrections to the
non-relativistic Hamiltonian are taken into account through the Breit-Pauli
approximation. We have also introduced a semi-empirical correction (TEC) for
the calculation of the energy-levels. These atomic data are used to provide
semiclassical electron-, proton- and ionized helium- impact line widths and
shifts for 15 Si VI muliplet. Calculated results have been used to consider the
influence of Stark broadening for DO white dwarf atmospheric conditions.Comment: MNRAS, accepted, 14 page
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