H2Diffraction from a Strained Pseudomorphic Monolayer of Cu Deposited on Ru(0001)

Diffraction of H2from surfaces is considered to be a useful tool to characterize molecule/surface interactions and surface topology. In this work, we have studied diffraction of H2from a strained pseudomorphic monolayer of Cu deposited on Ru(0001), both experimentally and theoretically. Our experimental measurements show a remarkable diffraction probability, both in-plane and out-of-plane. In particular, we observe for the first time third-order diffraction peaks. These striking experimental results have been analyzed by performing theoretical simulations, using both quantum and quasi-classical dynamics methods. Taking into account the relationship between diffraction (quantum phenomenon) and reflection (classical observable), we have performed a classical analysis of a meaningful set of classical trajectories. This analysis reveals that for H2/Cu/Ru(0001) diffracted molecules practically explore the entire surface unit cell and are able to get close to the surface, thus favoring high-order diffraction.