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Abstract:
The dissociative chemisorption of hydrogen on Cs-predosed Ru(001) surfaces at 90 K has been investigated using high-resolution electron energy loss spectroscopy (HREELS) and thermal desorption spectroscopy (TDS). The sticking coefficient of H2 decreases strongly with Cs coverage and the bonding energy increases. A saturation coverage of about one monolayer of H can be chemisorbed independent of Cs coverage. Coadsorbed Cs does not change the vibrational properties of the H layer which are determined by the Ru(001) surface: for small H coverages there is one perpendicular mode at 85 meV, and at large coverages there are the parallel modes at 100 meV and the perpendicular mode at 140 meV compatible with a threefold hollow site. There is no evidence of hydride complexes at all Cs and H coverages.
