Effect of Electron-Electron Interaction on the Kinetic-Energy Distribution of Electrons Ejected from Solids by Slow Ions

A method is presented for detecting the effect of the interaction between fast Auger electrons inside a solid (up to about 12 eV above the vacuum level) and band electrons of the solid. The fast electrons are produced by Auger neutralization of noble-gas ions at the solid surface, and their interaction with band electrons is observed in the change with incident ion energy of the kinetic-energy distribution of ejected electrons measured outside the solid. As incident ion energy is increased, the number of faster Auger electrons increases, which, in turn, increases the number of secondary electrons produced by them inside the solid. Data on Ge and Ni are presented here. Numerical estimates, based on the observed changes in kinetic-energy distribution and the assumption of a linear probability of secondary formation having a threshold at 4.5 eV, indicate that the secondary component for 4-eV ions amounts to about 10% of the total electron distribution for ${\mathrm{He}}^{+}$ on Ge(111), 8% for ${\mathrm{Ne}}^{+}$ on Ge(111), 4% for ${\mathrm{He}}^{+}$ on Ni(111), and 2% for ${\mathrm{Ne}}^{+}$ on Ni(111).