Polarization of the nf → 3d (n=4, 5, 6) x-rays from tungsten ions following electron-impact excitation and dielectronic recombination processes

Electron-impact excitation and resonant electron capture cross sections to the specific magnetic sublevels as well as the polarization of the strong nf→3d (n=4, 5, 6) x-ray emitted from Ni-like through Ge-like tungsten ions have been studied systematically by using a fully relativistic distorted-wave method. We compare the polarizations for the same x-ray but from the above two different processes for the first time. It is found that the polarization degrees of x-ray following both the electron-impact excitation and the dielectronic recombination are totally different. Because the electron-impact excitation dominates in hot and dense plasmas and the dielectronic recombination plays a key role in low-density plasmas which are cooled and recombining by capturing continuum electrons, we hope that the specific plasmas conditions could be assessed by using these x-ray polarizations. - Highlights: • EIE and REC cross sections of W42+–W46+ ions are calculated for the first time. • Polarizations of strong nf→3d x-ray lines from EIE and DR are calculated. • The polarizations for the same line but from EIE and DR are found to be different. • The present results are expected be used for plasma diagnosis in ITER