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Abstract:
The adsorption of hydrogen on Rh(110) has been studied by high resolution electron energy loss spectroscopy (HREELS) in the two high-symmetry directions at coverages corresponding to the formation of the various ordered overlayers. The minima of the reflectivity have been determined by measuring the intensity of the elastic beam as a function of the primary electron energy in order to exploit the increase of the inelastic cross section for vibrational excitation at those energies. The observed losses are assigned to the three modes of hydrogen adsorbed in pseudo-threefold hollow sites similar to those on the (111) surface. From a careful application of the HREELS selection rules it is concluded that the formation of hydrogen double chains at coverages above θ = 0.5 leads to a drastic frequency increase of the mode which is polarized along the chain direction.
