Secondary electron yields from low energy, highly charged ions impacting on metal surfaces

Ions impacting on a metal surface cause electrons to be emitted with their yield (number of emitted electrons per incoming ion) depending on the surface, impact angle, ion species, charge state, and energy. Previous investigations for low charge states and low impact velocities has shown that the number of secondary electrons are proportional to the ion`s potential energy (sum of ionization energies), but does not vary much with the impact velocities. Our results from 4-fold through 18-fold ionized Argon ions impacting on a 304 stainless steel Faraday cup show that the highest charge states emit substantially less than the number of electrons predicted by the ions potential energy. In, addition, we found an increase of approximately 8 electrons when the ion energy was raised from 1 keV/amu to 10 keV/amu.