AVS 47th International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP27
Ion Desorption from Molybdenum Oxide by Specific Core-to-Valence Resonant Excitations at the Mo L@sub 2,3@, Mo M@sub 2,3@ and O K-edges

Tuesday, October 3, 2000, 5:30 pm, Room Exhibit Hall C & D

Session: Poster Session
Presenter: Y. Baba, Japan Atomic Energy Research Institute, Japan
Authors: G. Wu, Japan Atomic Energy Research Institute, Japan
Y. Baba, Japan Atomic Energy Research Institute, Japan
I. Shimoyama, Japan Atomic Energy Research Institute, Japan
T. Sekiguchi, Japan Atomic Energy Research Institute, Japan
Correspondent: Click to Email
Irradiation of X-rays on solid surface induces various chemical changes such as decomposition and desorption. Due to the localized nature of inner-shell electrons, the primary excitation localizes around specific element or specific chemical bond. The question is whether or not the primarily localized excitation leads to the specific chemical reaction. The examples for specific chemical-bond scission and ion desorption induced by core-level excitation have been reported for adsorbed molecules on solid surfaces. Here we present the results for the ion desorption from bulk material induced by a specific core-to-valence resonant excitation. Molybdenum trioxide was chosen as a sample, because this material is known to be sensitive to irradiation of X-ray or electrons. In the X-ray absorption near-edge structure (XANES) spectra, the resonance peaks corresponding to the excitations from Mo2p to 4d have two components due to the ligand-field splitting of 4d state, which are assigned as transitions from Mo 2p to triply degenerated t@sub 2g@-type orbits and doubly degenerated e@sub g@-type orbits. When we compare the desorption-yield curves with XANES spectra taken by total electron yield, the O@super +@ ion yield at the resonance from Mo 2p@sub 3/2@ into the e@sub g@-type orbits was enhanced compared to that into the t@sub 2g@-type orbits. Similar enhancements were also observed for the Mo M@sub 3@ and O K-edge excitations. Considering the antibonding character of the e@sub g@-type orbits, the enhancement of desorption is explained by the localization of excited electrons in the e@sub g@-type orbits which leads to the specific Mo-O bond breaking and O@super +@ desorption. The detailed mechanism will be presented on the basis of the results for the Auger decay spectra.