Bibcode
Sahal-Bréchot, S.; Derouich, M.; Bommier, V.; Barklem, P. S.
Bibliographical reference
Astronomy and Astrophysics, Volume 465, Issue 2, April II 2007, pp.667-677
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4
2007
Journal
Citations
14
Refereed citations
11
Description
Context: Interpretation of linearly polarized parameters of the lines of
complex atoms for the second solar spectrum needs a lot of collisional
coefficients which are often poorly known. Aims: We provide
general and simple formulae giving the coefficients of the atomic master
equation (depolarization, polarization transfer, population transfer,
and relaxation coefficients) for the case of any atomic level (but not a
spherically symmetric) that is perturbed by collisions with hydrogen
atoms. Methods: We use the theory of the density matrix and the
theory of atomic collisions with a few assumptions (frozen core and spin
neglected during the collision). We only study collisional transitions
between levels of the same configuration with no equivalent electrons in
the external shell, and with the rest of the configuration (the core)
frozen. We use the basis of the Tkq irreducible
spherical tensor operators. Results: The formulae giving the
depolarization and polarization transfer coefficients due to collisions
with neutral hydrogen for l ≠ 0 levels of complex atoms can be
expressed as a linear combination of the k-pole depolarization and
elastic collisional rate coefficients obtained for simple atoms. Conclusions: .It should be possible to apply this method for fast
calculation of multipole rates for any level having an external shell l
≠ 0.