Influence of the Breit interaction on linear polarization of radiation lines following electron-impact excitation of the boron isoelectronic sequence

Abstract

Electron-impact excitation cross sections from the ground state $1{s}^{2}2{s}^{2}2{p}_{1/2}$ to the excited states ${[{(1{s}^{2}2s2{p}_{1/2})}_{0}2{p}_{3/2}]}_{3/2}$, ${[{(1{s}^{2}2s2{p}_{3/2})}_{1}2{p}_{3/2}]}_{5/2}$, ${[{(1s2{s}^{2}2{p}_{1/2})}_{0}2{p}_{3/2}]}_{3/2}$, and ${[{(1s2{s}^{2}2{p}_{3/2})}_{1}2{p}_{3/2}]}_{5/2}$ of highly charged boronlike ${\mathrm{Ca}}^{15+}$, ${\mathrm{Xe}}^{49+}$, and ${\mathrm{W}}^{69+}$ ions have been calculated with the fully relativistic distorted-wave method. The degrees of linear polarization of the corresponding radiation lines are further obtained. It is found that the Breit interaction makes the lines corresponding to the $2p\ensuremath{\rightarrow}2s$ transition depolarized, and it makes the ones corresponding to the $2p\ensuremath{\rightarrow}1s$ transition more polarized. These characteristics are very different from the results obtained for the linear polarization of the same radiation lines but formed via the dielectronic recombination process [Phys. Rev. A 91, 042705 (2015)], in which the Breit interaction has no effect on the linear polarization.