CS5P AND 4D PHOTOELECTRON LINEWIDTHS OF CS RU(001) - IMPLICATION FOR CS-RU INTERACTION AT THE INTERFACE/

Photoelectron linewidths of Cs5p and 4d levels of Cs adsorbed on Ru(00 1) for a series of coverages varying from submonolayer to multilayer h ave been examined. It is found that linewidth broadening for Cs atoms in direct contact with Ru occurs for both levels when compared with th at of bulk Cs atoms, and that while Cs4d levels broaden slightly but p ersistently over the entire range of coverage, the 5p linewidth exhibi ts a sharp change between Cs atoms that are in direct contact with the Ru substrate and those that are not; that is at submonolayer, monolay er and thin multilayer coverage, the Cs5p peak of the Cs atoms which a re in direct contact with the Ru substrate broadens considerably in co mparison with the Cs5p peak of the Cs atoms in the second overlayer an d in Cs metal. The Cs5p linewidth broadening is attributed primarily t o the relatively short lifetime of the core hole resulting from a fast Coster-Kronig/super Coster-Kronig decay channel facilitated by Cs-Ru interaction at the interface. This channel, which is absent in the pri mary decay of the Cs4d core hole, has little effect on the 4d linewidt h. This Cs5p linewidth broadening appears to be general for Cs in dire ct contact with any metal substrate and is discussed in terms of a s-d charge redistribution (rehybridization) model with the assistance of relativistic Dirac-Fock calculations. The less dramatic Cs4d broadenin g is attributed to a combined effect of interfacial phonon, chemical i nhomogeneity and crystal filed broadening.