Electron emission inHe+-atom andHe+-molecule collisions: A combined experimental and theoretical study

An experimental and theoretical study of the electron emission, differential in emission angle and energy, is presented for ${\mathrm{He}}^{+}$ impact on several gaseous targets. Experimentally, data at 400-, 500-, and 750-keV/amu impact on He, Ne, Ar, Kr, and ${\mathrm{H}}_2$O are presented; theoretically, cross sections for He and Ar are calculated using the first-order Born approximation. By measuring the total electron emission, as well as electron-scattered projectile coincidences, contributions to the differential cross sections resulting from projectile ionization, from target ionization, and from simultaneous projectile-target ionization events are identified. Theoretical cross sections for each of these processes, as well as their total sum, are compared with the experimental data. From these comparisons, it is found that the present theoretical treatment does a reasonable job of describing the total projectile and target ionization cross sections, but is poor for the double-differential cross section. It also severely underestimates the simultaneous projectile-target ionization cross section.