Degrees of polarization of the two strongest5f→3dlines following electron-impact excitation and dielectronic recombination processes of Cu-like to Se-like gold ions

Abstract

Cross sections for electron-impact excitation and capture to individual magnetic sublevels of Cu-like to Se-like gold ions have been calculated by using a fully relativistic distorted-wave (RDW) method. These magnetic cross sections have further been used to obtain the degrees of linear polarization for the first two strongest $5f\ensuremath{\rightarrow}3d$ radiative lines. A detailed comparison has been made between polarizations of these lines from the electron-impact excitation process and those of the same lines but from the dielectronic recombination process. It is found that for a Cu-like gold ion the polarization in the electron-impact excitation process increases sharply before starting to decrease at higher incident electron energies, and it reaches the maximum at around twice the threshold energy. The situations for other gold ions are very similar. However, as for the dielectronic recombination process, the polarization changes among a very large range with different gold ions. Therefore, the obvious differences between the polarizations from different formation processes can be employed in diagnosing the formation mechanism of the corresponding lines.