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Astron. Astrophys. 358, 373-377 (2000)

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Ab initio calculation of the transfer and multipole rates of the Na ground state hyperfine levels perturbed by atomic hydrogen

B. Kerkeni, A. Spielfiedel and N. Feautrier

DAMAP and UMR 8588 du CNRS, Observatoire de Paris, 92195 Meudon Cedex, France (Boutheina.Kerkeni,Annie.Spielfiedel,Nicole.Feautrier@obspm.fr)

Received 8 February 2000 / Accepted 11 April 2000


A theoretical treatment of the multipole relaxation and transfer rates due to isotropic collisions is presented. Explicit expressions are obtained for the collisional rate constants of the hyperfine-structured ground level of the Na I atoms perturbed by collisions with H atoms. As the effects of Na nuclear spin during the collision are negligible, it is shown that all the rate constants involve the same electronic relaxation rate of the multipole of rank one. Evaluation of these rates has been carried out using very accurate potential energy curves.The formulae given here for the depolarizing collisional rates should be useful for accurately modeling the complex linear polarization pattern of the Na I doublet that can be observed in quiet regions of the solar atmosphere using spectro-polarimeters of high polarimetric sensitivity.

Key words: atomic processes – line: formation – polarization – Sun: atmosphere

Send offprint requests to: A. Spielfiedel

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© European Southern Observatory (ESO) 2000

Online publication: June 26, 2000