Absolute cross-section measurements for electron-impact ionization of Al+, Cd+, and Hg+

Absolute cross sections for single ionization of Al+, Cd+, and Hg+ by electron impact have been measured for electron energies from threshold to 2 keV using the crossed-beams technique. The Al+ cross section shows a peak value of (74 +- 6) x 10/sup -18/ cm2 at about 46 eV. In addition, for Al+ there is significant structure around 80 eV, an energy corresponding to the 2p53s2nl autoionizing states of Al+. The Cd+ and Hg+ cross sections show no major structures and have peak values of (147 +- 6) x 10/sup -18/ cm2 and (169 +- 5) x 10/sup -18/ cm2, respectively, both at an electron energy of roughly 100 eV. Comparisons are made to semiempirical and theoretical predictions and to other existing experimental data