Ionization to specific magnetic sublevels by an electron beam: Application to the effect of inner-shell ionization on the polarization ofSe24+lines

A procedure for treating excitation of ions to specific magnetic sublevels by an electron beam is modified to apply for ionization. This is then used in the study of the linear polarization of the three x-ray lines ${(2p}^{5}{3s)}_{1,2}\ensuremath{\rightarrow}{(2p}^{6}{)}_{0}$ emitted by ${\mathrm{Se}}^{24+}.$ We do this by including population of the upper levels by innershell ionization of Na-like Se in addition to excitation from the ${(2p}^{6}{)}_{0}$ ground level of Ne-like Se both directly and via cascades from higher $n=3$ levels. The required cross sections for both excitation and ionization to individual magnetic sublevels were computed in a fully relativistic distorted-wave method at impact energies ranging from 190 to 800 Ry. The radiative branching ratios were calculated using the fully relativistic GRASP atomic structure code. It is found that the innershell ionization process is almost unselective in populating the different $|M|$ sublevels of each upper level. Small values of the polarization degrees are obtained due to the combined effects of radiative cascades and inner-shell ionization.