Bibcode
Belluzzi, L.; Landi Degl’Innocenti, E.; Trujillo Bueno, J.
Bibliographical reference
The Astrophysical Journal, Volume 812, Issue 1, article id. 73, 12 pp. (2015).
Advertised on:
10
2015
Journal
Citations
4
Refereed citations
4
Description
A correct modeling of the scattering polarization profiles observed in
some spectral lines of diagnostic interest, the sodium doublet being one
of the most important examples, requires taking hyperfine structure
(HFS) and quantum interference between different J-levels into account.
An atomic model suitable for taking these physical ingredients into
account is the so-called multiterm atom with HFS. In this work, we
introduce and study the transfer and relaxation rates due to isotropic
inelastic collisions with electrons, which enter the statistical
equilibrium equations (SEE) for the atomic density matrix of this atomic
model. Under the hypothesis that the electron–atom interaction is
described by a dipolar operator, we provide useful relations between the
rates describing the transfer and relaxation of quantum interference
between different levels (whose numerical values are in most cases
unknown) and the usual rates for the atomic level populations, for which
experimental data and/or approximate theoretical expressions are
generally available. For the particular case of a two-term atom with
HFS, we present an analytical solution of the SEE for the spherical
statistical tensors of the upper term, including both radiative and
collisional processes, and we derive the expression of the emission
coefficient in the four Stokes parameters. Finally, an illustrative
application to the Na i D1 and D2 lines is
presented.
Related projects
Magnetism, Polarization and Radiative Transfer in Astrophysics
Magnetic fields pervade all astrophysical plasmas and govern most of the variability in the Universe at intermediate time scales. They are present in stars across the whole Hertzsprung-Russell diagram, in galaxies, and even perhaps in the intergalactic medium. Polarized light provides the most reliable source of information at our disposal for the
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