We report observations of extremely energetic electrons produced in collisions between keV ${\mathrm{He}}^{+}$ and ${\mathrm{Ar}}^{+}$ and different solid surfaces, with energies up to approximately 40% of the center-of-mass energy. This emission can result from the decay of many-electron excitations produced in nearly head-on collisions.

• Received 13 September 1991

DOI:https://doi.org/10.1103/PhysRevA.45.5286