Theoretical results of quantum-mechanical model calculations for an Eley-Rideal reaction are presented and related to the topology and energetics of the underlying potential energy surface. The Eley-Rideal PES is more exo-energetic as compared to the Langmuir-Hinshelwood case and the reaction path shows more curvature. Both features lead to stronger vibrational excitations. The model is applied to recently observed strong vibrational excitation of H 2 formed by atomic recombination on a tungsten surface. It turns out that, as a consequence of energy conservation, the population of the highest levels can only be explained if unusually low binding energies of the preadsorbed hydrogen atoms are assumed.