Excited atom emission under ion bombardment of metal surfaces covered by alkaline films

Abstract

The photon yield, Y, emitted from excited Al and Cu atoms sputtered and scattered under ion bombardment of clean and Cs-covered surfaces has been measured. It is shown that the value of Y 1 for excited sputtered atoms is independent of Cs-coverage degree. By contrast, the value of Y 2 for excited scattered atoms drastically increases (by a factor of 10) with Cs coating. Such sharp differences in the behavior of Y 1 and Y 2 values may be explained by the different characteristic times for the cascade sputtering (ρ <≈ 10 −13 s) and scattering (ρ ≈ 10 −15 s) processes. We propose that the incident ion generating a sputtering cascade induces the desorption of adsorbated Cs atoms during the period characteristic for the scattering time. Therefore, the excited state of sputtered atoms unlike that of the scattered ones is formed by electron exchange with the local clean surface area.