Ion desorption from surfaces following photon excitation of core electrons in the bulk

Comparison of photon-excited total electron yield and H⁺-ion yield spectra above the N K edge and Ni L edge for single and multiple NH₃ layers on Ni(110) reveal the dominance of an indirect ion-desorption mechanism. This mechanism consists of photon excitation in the bulk with long-range transfer of the excitation to the surface by secondary electrons. Our results imply important limitations in the existing picture of the electron- and photon-stimulated-desorption techniques as site-specific, local surface probes.