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Adsorption dynamics of O 2 on Cu͑100͒ and on reconstructed Cu͑100͒-͑2 ͱ 2 ϫ ͱ 2͒R45°-O at 300 and 553 K have been investigated by employing a supersonic molecular-beam surface-scattering technique. Experimental results suggest that an activated direct adsorption channel is operative on the clean Cu͑100͒, whereas the adsorption of O 2 on the reconstructed Cu͑100͒ is mediated either by a precursor state or by steering effects. First-principles molecular-dynamics simulations and potential-energy surface calculations show that the nature of the adsorption dynamics of O 2 is different between the clean and reconstructed Cu͑100͒ surfaces. The O 2 molecule is likely to diffuse away from the reconstructed area or to completely desorb from the surface, while in the case of the clean Cu͑100͒ surface, the adsorption occurs through a direct dissociative trajectory. We also find that in the case of the reconstructed surface, the steering occurs higher over the surface and that the recoil effect does not modify the surface as much as in the case of the clean surface. Moreover, the mobility of O and Cu adatoms on the reconstructed Cu surface is significantly lower than that on the clean surface both in the direction of the missing rows and in the direction perpendicular to them.

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