Energy spectrum shape of low energy ion scattering from insulators and its similarity to asymmetric spectrum shape observed in core level XPS from metals

The energy spectrum of low energy ion scattering (LEIS) from insulators is studied theoretically. The energy spectrum could be analyzed by using the Doniach–Sunsic line-shape function, which is routinely used as a fitting function to the asymmetric shape of the spectrum observed in core level X-ray photoemission spectroscopy (XPS) for metallic targets. The common nature between LEIS and XPS is discussed in terms of a singular behavior of physical processes involved in LEIS and XPS. In the case of XPS, it is known that the infrared divergence of electron–hole pair excitations leads to the asymmetric shape of line spectrum, whereas, in the case of LEIS, the multiple elastic scatterings lead to a similar asymmetric shape of the spectrum.