Hot-atom mechanism in hydrogen exchange reaction on the Ir{100} surface

H2 exposure was found to induce the desorption of HD and D2 molecules from the D-precovered Ir{100} surface. This result suggests that energetic H atoms (hot H atoms) produced in the dissociation process of incident H2 molecules react with pre-adsorbed D atoms and desorb as HD molecules or produce secondary energetic D atoms via energy transfer. Secondary energetic D atoms (secondary hot D atoms) also induce the associative reactions with pre-adsorbed D atoms and desorb as D2 molecules.