Données collisionnelles pour le modèle PACR (population-alignment collisional-radiative) utilisé dans la spectroscopie des plasmas chauds anisotropes

Abstract

An expression for the multipole components of cross sections for excitation of ions by impact with directive electrons has been derived for the first time within the framework of the relativistic distorted Wave approach, taking into account the coherence between the magnetic sublevels. These cross sections are needed in the interpretation of lines emitted from non-thermal hot plasmas whose free electrons are characterized by velocity distributions having cylindrical symmetry. In order to compute this collisional data, we introduced modifications in the magnetic-sublevel excitation program of the flexible atomic code (FAC). Detailed calculations were carried out for transitions in the beryllium-like ion O4+ from the ground 2s2 1S0 and metastable 2s2p 3P 0,1,2 levels. Various results for transitions from 2s2p 3P1,2 to 2s3p 3P1,2 and 2s3d 3D2,3 levels, which have a great interest in the solar atmosphere and tokamak plasmas, are presented in this thesis to illustrate the application of the modified program proposed here. An indepth analysis of the numerical results and a preliminary comparison with the data available in the literature allowed a systematic consistency of the modified program, paving the way for the calculations of a large amount of multipole excitation cross-section data with a considerable saving of time.