Absolute cross-section measurements for electron-impact ionization of ${\mathrm{Al}}^{+}$, ${\mathrm{Cd}}^{+}$, and ${\mathrm{Hg}}^{+}$

Absolute cross sections for single ionization of ${\mathrm{Al}}^{+}$, ${\mathrm{Cd}}^{+}$, and ${\mathrm{Hg}}^{+}$ by electron impact have been measured for electron energies from threshold to 2 keV using the crossed-beams technique. The ${\mathrm{Al}}^{+}$ cross section shows a peak value of (74±6)×${10}^{\mathrm{-}18}$ ${\mathrm{cm}}^2$ at about 46 eV. In addition, for ${\mathrm{Al}}^{+}$ there is significant structure around 80 eV, an energy corresponding to the 2$p^5$3$s^2$nl autoionizing states of ${\mathrm{Al}}^{+}$. The ${\mathrm{Cd}}^{+}$ and ${\mathrm{Hg}}^{+}$ cross sections show no major structures and have peak values of (147±6)×${10}^{\mathrm{-}18}$ ${\mathrm{cm}}^2$ and (169±5)×${10}^{\mathrm{-}18}$ ${\mathrm{cm}}^2$, respectively, both at an electron energy of roughly 100 eV. Comparisons are made to semiempirical and theoretical predictions and to other existing experimental data.