Collision-Strength Shift in Electron-Impact Single and Double Ionization of Sb and Bi Ions

At energies greater than 200 eV the electron-impact single-ionization cross sections for ${\mathrm{Sb}}^{2+}$($4d^{10}5s^{2}5p$) and ${\mathrm{Bi}}^{2+}$($5d^{10}6s^{2}6p$) ions, ${\sigma }_{2,3}$, are larger than the corresponding cross sections, ${\sigma }_{1,2}$, for ${\mathrm{Sb}}^{1+}$ and ${\mathrm{Bi}}^{1+}$ ions, respectively. This extraordinary behavior is a consequence of the fact that the $4d\left(5d\right)\mathrm{}$ hole configurations goes from autoionization to bound when the charge state of the Sb (Bi) ions is increased from +1 to +2. Additionally, multiple ionization measurements (${\sigma }_{1,3}$ for Sb and ${\sigma }_{1,3}$, ${\sigma }_{2,4}$, and ${\sigma }_{3,5}$ for Bi) are presented for electron energies up to about 1000 eV.