Electron Impact Excitation of Fine‐Structure Levels in Sulfur‐like Fe xi

Abstract

Collision strengths for electron impact excitation of fine-structure levels in sulfur-like Fe XI are calculated in a semirelativistic R-matrix approach. The 38 fine-structure levels arising from the 20 LS states 3s23p43P,1D,1S; 3s3p53Po,1Po; 3s23p3(4So)3d3Do, 3s23p3(2Po)3d1,3Po,1,3Do,1,3Fo, 3s23p3(2Do)3d1,3So,1,3Po,1,3Do,1,3Fo are included in our calculation. The target levels are represented by configuration interaction wave functions. The relativistic effects are considered in the Breit-Pauli approximation by including one-body mass correction, Darwin term, and spin-orbit terms in the scattering equations. Collision strengths for transitions from the 3s23p43P2,1,0 levels to the fine-structure levels of the 3s23p33d configuration are compared with the distorted-wave results of Bhatia & Doschek at 8.0, 16.0, 24.0 ryd. There are some significant discrepancies between the two calculations, mostly caused by the difference in target wave functions. The collision strengths are integrated over a Maxwellian distribution of electron energies to obtain effective collision strengths over the temperature range from 5 × 105 to 5 × 106 K.