Fast-Electron-Slow-Electron Coincidence Study of ViolentAr+-Ar Collisions

An electron-electron coincidence measurement has been made of the energy spectrum of only those slow electrons emitted from violent ${\mathrm{Ar}}^{+}$-Ar collisions that produce known energy, fast $L\to \mathrm{MM}$ Auger electrons. The correlation between the number of ejected slow electrons and the energy of the fast electron is much less than expected from a model based on the generally assumed ordering of the inner-shell (Auger) and outer-shell transitions following inner-shell excitation. Furthermore, details of the spectra show that double Auger ($L\to \mathrm{MMM}$) processes do not occur in a large percentage of the events studied. It appears that the branching ratio of outer-shell auto-ionizing transitions to $L\to \mathrm{MM}$ transitions in argon is smaller than expected, possibly owing to the molecular properties of the ${\mathrm{Ar}}^{+}$-Ar collision system.