EDP Sciences
Free access
Volume 404, Number 2, June III 2003
Page(s) 763 - 773
Section Celestial mechanics and astrometry
DOI http://dx.doi.org/10.1051/0004-6361:20030568

A&A 404, 763-773 (2003)
DOI: 10.1051/0004-6361:20030568

Semi-classical theory of collisional depolarization of spectral lines by atomic hydrogen I. Application to p states of neutral atoms

M. Derouich1, S. Sahal-Bréchot1, P. S. Barklem2 and B. J. O'Mara3

1  Observatoire de Paris-Meudon, LERMA UMR CNRS 8112, 5 place Jules Janssen, 92195 Meudon Cedex, France
2  Department of Astronomy and Space Physics, Uppsala University, Box 515, S 751 20 Uppsala, Sweden
3  Department of Physics, The University of Queensland, St Lucia 4072, Australia

(Received 29 November 2002 / Accepted 4 April 2003)

The present paper extends the method of Anstee, Barklem and O'Mara (Anstee 1992; Anstee & O'Mara 1991, 1995; Anstee et al. 1997; Barklem 1998; Barklem & O'Mara 1997; Barklem et al. 1998), developed during the 1990s for collisional line broadening by atomic hydrogen, to the depolarization of spectral lines of neutral atoms by collisions with atomic hydrogen. In the present paper, we will limit the calculations to p ( l=1) atomic levels. The depolarization cross sections and depolarization rates are computed. In Table [see full text] cross sections as functions of the relative velocity and effective quantum number are given, allowing for the computation for any p atomic level. Our results are compared to quantum chemistry calculations where possible. The sensitivity of depolarization cross sections to regions of the potential is examined. We conclude that the accuracy obtained with our method ( <20% for the depolarization rates) is promising for its extension to higher l-values for the interpretation of the "second solar spectrum". This will be the object of further papers.

Key words: Sun: atmosphere -- atomic processes -- line: formation -- polarization -- atomic data

Offprint request: M. Derouich, Moncef.Derouich@obspm.fr

© ESO 2003

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