Tunnel ionization of K and L shells model for enhanced X-ray emission by charged up materials

Abstract

Abstract Enhanced X-ray emission from insulator samples charged up during ion beam irradiation, is an effect well known in the particle induced X-ray emission (PIXE) community. Still, its physical grounds remain to be established properly. According to the literature the effect was first observed by Terasawa in 1968, in the early days of PIXE. The effect was to be re-discovered in the 1990s decade, after which a significant attention was put on to it by various authors. Nevertheless, no consistent results and complete generally accepted explanation were reached, so far. Revisiting the problem based on a self-consistent analysis of old data and very recent observations, we have realised that only assuming the occurrence of inner shells tunnel ionization is it possible to explain all experimental details, in particular some that have not been properly justified until now. This conclusion, presents itself of major importance for the PIXE and ion beam communities, but furthermore its relevance extends well beyond this frame by bringing to light, the occurrence of tunnelling ionization of deep energy levels, induced by ion beams, and without the intervention of intense laser beams.