Electron-impact ionization ofZn+andGa+

Abstract

Absolute cross sections for electron-impact ionization of ${\mathrm{Zn}}^{+}$ and ${\mathrm{Ga}}^{+}$ have been measured from below threshold to 2 keV with the use of the crossed-charged-beams technique. Excitation autoionization was shown to be of major importance in both ions for the region between 1 and 2 times threshold, leading to enhancement of the cross sections by factors of up to ∼2.5. Discrepancies between experiment and the well-known semi-empirical formula of Lotz were up to 70%, but reduction of Lotz's $a_{3d}$ coefficient by a factor of 2 leads to satisfactory agreement at high energies. Comparison is also made with scaled-Born-approximation calculations.