Dynamic displacement of O2 from Pt(111): A new desorption mechanism

Exposing an O2-covered Pt(111) surface to beams of O, N, and H atoms leads to prompt desorption of the O2, which leaves the surface with a bimodal velocity distribution that appears the same in each case, but which is different from that obtained for thermal desorption. We propose that the O2 molecules are directly displaced by the incident atoms and that part of the adsorption energy is carried away by the desorbing species. Photodesorption at 213 nm gives an identical velocity distribution, indicating that a similar displacement mechanism may operate.