EXCITED ATOM EMISSION UNDER ION-BOMBARDMENT OF METAL-SURFACES COVEREDBY ALKALINE FILMS

The photon yield, Y, emitted from excited Al and Cu atoms sputtered an d scattered under ion bombardment of clean and Cs-covered surfaces has been measured. It is shown that the value of Y1 for excited sputtered atoms is independent of Cs-coverage degree. By contrast, the value of Y2 for excited scattered atoms drastically increases (by a factor of 10) with Cs coating. Such sharp differences in the behavior of Y1 and Y2 values may be explained by the different characteristic times for t he cascade sputtering (tau almost-equal-to 10(-13) s) and scattering ( tau almost-equal-to 10(-15) s) processes. We propose that the incident ion generating a sputtering cascade induces the desorption of adsorba ted Cs atoms during the period characteristic for the scattering time. Therefore, the excited state of sputtered atoms unlike that of the sc attered ones is formed by electron exchange with the local clean surfa ce area.