Absolute cross sections for electron-impact single ionization of ${\mathrm{Si}}^{+}$ and ${\mathrm{Si}}^{2+}$ have been measured using crossed beams of ions and electrons and calculated using a configuration-average distorted-wave method. Corrections have been made for metastable components and small fractions of nitrogen impurities in the incident ion beams. Excitation-autoionization measurably enhances the cross sections of both ${\mathrm{Si}}^{+}$ and ${\mathrm{Si}}^{2+}$. Ionization rate coefficients and fitting parameters are presented for the experimental data.

• Received 18 January 1993

DOI:https://doi.org/10.1103/PhysRevA.47.4786