Extended ion--electron coincidence measurements of the violent Ar+ + Ar collision

The energy spectra of electrons ejected from 25-keV Ar⁺ + Ar collisions have been measured. By employing the coincidence technique we were able to study specifically those electrons from collisions in which the projectiles were scattered through a known angle, θ=21°±2°, and were ionized to a known final charge m. Data were taken in the range of ejected-electron energies from 10 to 250 eV. The data reveal both fast electrons produced by Auger transitions which fill vacancies in the inner (L) shell and slow electrons produced by excitation of the outer (M) shell. A detailed examination of our spectra supports the conclusion that slow electrons may be ejected after as well as before the Auger event. Furthermore, the ratio of the number of fast Auger electrons to the number of slow electrons observed indicates that most inner-shell vacancies are filled after the ions have separated to a considerable extent.