Variation of Surface Reaction Probability with Reactant Angle of Incidence: A Molecular Beam Study of the Asymmetry of Stepped Platinum Crystal Surfaces for H-H Bond Breaking

A molecular beam of ${\mathrm{H}}_2$ and ${\mathrm{D}}_2$ was used to investigate the angular dependence of the reaction probability for ${\mathrm{H}}_2$-${\mathrm{D}}_2$ exchange (${\mathrm{H}}_2$+${\mathrm{D}}_2$→2HD) on the Pt(111) and $\mathrm{Pt}\mathrm{}\left(s\right)\mathrm{}$-[6(111)× (111)] surfaces. On the stepped surface, a marked increase in the production of HD is observed when the beam of reactants strikes the open side of the step structure. The Pt(111) surface exhibits a smooth decrease in HD production from normal incidence to grazing angles.