Double differential electron emission yields following the impact of fast (3.95×${10}^7$cm/sec)${\mathrm{Ar}}^{9,12,18+}$, ${\mathrm{Ne}}^{9+}$, ${\mathrm{Xe}}^{30,44+}$, and ${\mathrm{Th}}^{70,75+}$ ions on Cu and Au targets have been measured. The electron emission is dominated by low-energy electrons (<50 eV). It is found that the total yield, which rises to about 100 electrons per ion, is a nonlinear function of the total potential energy of the incident ion (up to about 200 keV).

• Received 25 November 1991

DOI:https://doi.org/10.1103/PhysRevLett.68.2297