Multiple ionization of rare gases byH+andHe+impact

Absolute cross sections for multiple ionization (${\sigma }_q$) of He, Ne, Ar, and Kr are presented for proton-impact energies between 10 and 4000 keV. Charge states up to 6+ are observed for Kr. The results are obtained by measuring relative yields of multiply charged ions with a time-of-flight spectrometer and normalizing to total ion-production cross sections ${\sigma }_T=\Sigma q{\sigma }_q$. The results are compared with existing proton- and electron-impact data. Relative multiple- to single-ionization cross-section ratios are also presented for ${\mathrm{He}}^{+}$ impact.