Catastrophic sputtering of sulfur by helium

Abstract
The sputtering yield of sulfur by 30-300 keV 4He+ at 20°C was found to be of the order of 104-106 sulfur atoms per incident 4He, dependent on the energy and total implanted fluence, and independent of the ion flux onto the target. This effect may be explained by a weakening of the van der Vaals binding between the S8 rings due to Coulomb repulsion in the homogeneously charged volume, after a sufficient charge has accumulated in the highly insolating sample. Sulfur emission continues even for some time after the beam is switched off, and emission of sulfur atoms is also observed from non-irradiated areas adjacent to the irradiated spot, even from the rear side of 2-mm thick sulfur targets.