Polarization of the x-rays from Fe ions following K-shell electron-impact excitation and dielectronic recombination

Abstract The total and magnetic sublevels cross sections both for the electron impact excitation (EIE) of C-like Fe 20+ ion from the ground state to the K -shell excited states <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:mn>1</mml:mn> <mml:mi>s</mml:mi> <mml:mn>2</mml:mn> <mml:msup> <mml:mrow> <mml:mi>s</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mn>2</mml:mn> <mml:msup> <mml:mrow> <mml:mi>p</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:msup> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> <mml:mrow> <mml:mi>J</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0</mml:mn> <mml:mo>,</mml:mo> <mml:mn>1</mml:mn> <mml:mo>,</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> </mml:math> and for the dielectronic recombination (DR) of B-like Fe 21+ ion to the same K -shell excited states have been calculated using a fully relativistic distorted-wave approach. Based on these results, the degrees of linear polarization for the same x-ray lines associated with strong 2 p → 1 s transitions have been obtained. Significant differences are observed in the polarizations of radiative x-rays from these two atomic processes, which can be employed to distinguish the formation mechanism of the corresponding x-ray lines.