Absolute cross-section measurements for electron-impact single ionization of Si4+ and Si5+

Abstract

Experimental measurements of absolute cross sections are presented for electron-impact single ionization of ${\mathrm{Si}}^{4+}$ and ${\mathrm{Si}}^{5+}$. The incident electron energies range from below threshold to 1500 eV. The measurements were performed using the crossed ion-electron beams apparatus at the Oak Ridge National Laboratory Electron-Cyclotron Resonance Ion-Source Facility. The data are in reasonable agreement with cross sections calculated using the Lotz semiempirical formula. Reduced cross sections for the isoelectronic targets, ${\mathrm{Si}}^{4+}$ and ${\mathrm{Ar}}^{8+}$, are compared in order to test classical scaling for direct electron-impact single ionization.