Resonant ion stimulated desorption of protons from cerium oxide

The emission of protons from the polycrystalline CeOx surface was investiga ted during noble-gas ion bombardment (E-0 < 2 keV), in comparison with low- energy proton scattering (E-0 = 100 eV). At the reduced CeOx surface, the p roton survives neutralization with a higher probability when scattered from oxygen than from cerium. The surface hydrogens are sputtered as protons by ion irradiation via the non-collisional electronic transition. The probabi lity for H+ desorption decreases in order of He+, Ne+ and Ar+. This is beca use hydrogen desorbs from the antibonding OH group with an O 2s core hole w hich is created via the quasi-resonant charge exchange with the primary ion s. The ionization of hydrogen occurs during the O-H bond breakage via the i nteratomic Auger decay of the O 2s hole. The resulting H+ ion survives neut ralization preferentially from O of CeO2 as confirmed from the H+ scatterin g experiment. On the basis of these findings, we propose resonant ion stimu lated desorption (RISD) as a tool for quite sensitive detection of surface hydroxyl group and apply it to in situ observations of hydrogen segregation to the surface. (C) 2000 Elsevier Science B.V. All rights reserved.