Dirac<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>R</mml:mi></mml:math>-matrix method for the calculation of x-ray line polarization

Abstract

We have developed a method within the Dirac $R$-matrix theory to calculate x-ray line polarization resulting from electron-impact excitation to excited-state magnetic sublevels of complex ions. We apply this method to the excitation of two well-known x-ray lines of Fe XVII, $3C$ $(\ensuremath{\lambda}=15.015\text{ }\text{\AA{}})$ and $3D$ $(\ensuremath{\lambda}=15.262\text{ }\text{\AA{}})$. We find strong resonance effects which contribute to complicated energy dependence in the polarization. Our results show large differences, up to 30% or more, from earlier theoretical work, and thus provide a stimulus for direct experimental measurement of the $3C$ and $3D$ line polarizations and further theoretical studies.