engleski

Assessment of the role of quantal effects in the dynamics of stimulated desorption

We have assessed the roles of various quantum effects in the stimulated desorption spectra and yields of isolated physisorbed species. By an appropriate extension of the semiclassical (Antoniewicz's) and strictly quantum wave-packet squeezing (WPS) models of desorption with dissipative coupling of the ionized adsorbate to the substrate electronic response, we were able to describe quantum effects associated with elastic and inelastic adsorbate motion within a unified model. Using this model we investigated the possibility of removing the long-standing discrepancies between large values of experimental desorption yields from adlayers of Ar atoms on Ru(001) and much smaller ones calculated in Antoniewicz's and WPS models by using empirical atom-surface potential parameters. The desorption rates thus calculated turned out to be rather insensitive to dissipative effects due to a smooth transition between Antoniewicz's and WPS desorption regimes, which could be explained by the properties of the wave packets describing the ionized adparticle motion. This indicated that the desorption rates would be sensitive only to the variations of the neutralization rate and parameters specifying neutral- and ionized-state diabatic potentials. By varying the latter we showed that high enough desorption yields could be reproduced only with extreme forms of the ionized-state potentials. From this we conclude that improved models of stimulated desorption need take into account certain aspects of the many-body lateral adsorbate-adsorbate interactions.

atom-solid interaction ; scattering ; diffraction ; electron stimulated desorption ; energy dissipation ; metallic surfaces ; models of surface chemical reactions ; single crystal surfaces

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