We excite low-coordinated surface sites of nanostructured MgO samples using 4.7 eV UV laser pulses and observe dominant hyperthermal O-atom emission. Excitation of the same samples with 7.9 eV photons results in thermal O-atom desorption. These results are analyzed in the context of laser desorption models developed previously for alkali halide crystals and MgO. We detail two multi-step mechanisms for hyperthermal O-atom desorption, under surface selective excitation, based on exciton and hole trapping at three-coordinated (corner) O-atom sites, and evaluate the validity of each based on available experimental data and calculated results. The proposed models are significantly different from and more complex than the surface exciton desorption model established for alkali halides. Nonetheless, the principles of site-specific photo-excitation and exciton and hole localization induced atomic desorption are clearly extendable to a prototypical metal oxide. © 2008 Elsevier B.V.

Energy and site selectivity in O-atom photodesorption from nanostructured MgO

Trevisanutto P. E.;
2008-01-01

Abstract

We excite low-coordinated surface sites of nanostructured MgO samples using 4.7 eV UV laser pulses and observe dominant hyperthermal O-atom emission. Excitation of the same samples with 7.9 eV photons results in thermal O-atom desorption. These results are analyzed in the context of laser desorption models developed previously for alkali halide crystals and MgO. We detail two multi-step mechanisms for hyperthermal O-atom desorption, under surface selective excitation, based on exciton and hole trapping at three-coordinated (corner) O-atom sites, and evaluate the validity of each based on available experimental data and calculated results. The proposed models are significantly different from and more complex than the surface exciton desorption model established for alkali halides. Nonetheless, the principles of site-specific photo-excitation and exciton and hole localization induced atomic desorption are clearly extendable to a prototypical metal oxide. © 2008 Elsevier B.V.
2008
Atom emission
Density functional calculations
Desorption induced by electronic transitions (DIET)
Excitons
Laser control
Magnesium oxides
Photon stimulated desorption (PSD)
Surface defects
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.12610/62761
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