Xenon adsorption on Pt-Pd alloy surfaces: comparison of calculations with experimental data

The adsorption of Xe on Pt-Pd alloy surfaces was studied using UV photoelectron spectroscopy. The alloy surfaces of different composition were prepared by depositing a film on the Pd(110) substrate and annealing to increasing temperatures. The initial Pt film exhibited a (110)(1 × 2) reconstruction. Increasing amounts of Pd diffusing through the Pt overlayer turned the surface structure back into an unreconstructed (110) topography. As an example, the Xe(5p32,12) UPS spectra obtained for different Xe coverages on a Pt-5% Pd alloy surface could be fitted with up to 4 Xe adsorption states taking the corresponding spectra from the clean Pt(110)(1 × 2) and Pd(110) surfaces as references. The relative adsorption energies (Ead) of Xe atoms at various sites on the alloy surface are discussed in the light of Lennard-Jones Xe-Pt and Xe-Pd pair-potential calculations.