RESONANT EFFECTS ON ELECTRON-IMPACT IONIZATION OF SODIUM-LIKE SELENIUM

We have calculated the resonant-excitation-double-autoionization (REDA ) cross sections for sodiumlike selenium. The REDA process is treated as a three-step process (i.e., resonant electron capture followed by s equential double Auger emission). The necessary atomic data are comput ed using the multiconfiguration Dirac-Fock model. The effects of radia tive damping can reduce the calculated REDA cross sections by a factor of 6, and the loss channels can further reduce these cross sections b y a factor of 2. The REDA processes produce many strong narrow resonan ces and contribute 10-20 % to the average total ionization cross secti ons.