EAS Publications Series
Volume 43, 2010Non-LTE Line Formation for Trace Elements in Stellar Atmospheres
|Page(s)||79 - 90|
|Published online||16 November 2010|
R. Monier, B. Smalley, G. Wahlgren and Ph. Stee (eds)
EAS Publications Series, 43 (2010) 79-90
Accurate Collisional Cross-Sections: Important Non-Lte Input Data
Institute of Astronomy, Russian Academy of Science,
Pyatnitskaya 48, 119017
Non-LTE modelling for a particular atom requires accurate collisional excitation and ionization cross-sections for the entire system of transitions in the atom. This review concerns with inelastic collisions with electrons and neutral hydrogen atoms. For the selected atoms, H i and Ca ii, comparisons are made between electron impact excitation rates from ab initio calculations and various theoretical approximations. The effect of the use of modern data on non-LTE modelling is shown. For most transitions and most atoms, hydrogen collisional rates are calculated using a semi-empirical modification of the classical Thomson formula for ionization by electrons. Approaches used to estimate empirically the efficiency of hydrogenic collisions in the statistical equilibrium of atoms are reviewed.
© EAS, EDP Sciences 2010
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