Electron impact excitation and polarization studies of Fe-like W⁴⁸⁺ to Al-like W⁶¹⁺ ions

A fully relativistic distorted wave theory has been employed to study electron impact excitations of specific magnetic sublevels in Fe-like W⁴⁸⁺ through Al-like W⁶¹⁺ ions. M-shell excitations, namely, 3p → 3d by electron impact have been considered in these 14 tungsten ions. Excitation cross sections are reported for incident electron energies from the threshold to 20 keV. In addition, for each transition, analytic fitting to the cross sections are provided. The degree of polarization of the emitted photons from the decay of the different excited anisotropic states of the tungsten ions is also calculated through the expressions we derived using density matrix theory in terms of magnetic sublevel excitation cross sections. (author)