Role of electron capture in ion-induced electronic sputtering of insulators

Measurements of the sputtering yield of solid O-2 by 25-240-keV H+ show that it is double valued in its dependence on electronic stopping power. We propose that this is because the electronic sputtering yield is dominated by repulsion of ions in the ionization track of the projectile which, at low velocities, is augmented near the surface due to the additional ionization resulting from electron captures. This process may also be responsible for enhanced radiation damage in insulators, in particular in the production of fission tracks.