SURFACE-TEMPERATURE EFFECTS IN THE DISSOCIATIVE ADSORPTION OF D-2/CU(111) REVISITED

We have calculated the dissociation probability of H-2 and D-2 on low dimensional potential energy surfaces (PESs) including substrate motion by attaching the PES to a simple harmonic oscillator or to a free mass. For all potentials examined, we find that the dissociation curve has a fixed midpoint while the width increases with surface temperature as observed experimentally. This is in agreement with earlier calculations by Hand and Harris and in disagreement with more recent ones. We conclude that the explanation of Hand and Harris, which ascribes the broadening to the approaching (receding) part of the oscillator phase increasing (decreasing) the relative velocity of the incident atom, is correct. This has the further consequence that the broadening is greater for D-2 than for H-2. We speculate that yet more broadening may be caused by thermally increased corrugation of the surface.