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Non-adiabatic reaction pathways in the dissociative adsorption of Oxygen on an Al(111) surface

Binetti, Marcello

In the present work the results of an experimental study on the inital stages of alumi-num oxidation are reported. Despite a long-standing theoretical and experimental effort, this process still presents some puzzling characteristics. Among them, the direct, activated character of the chemi-sorption process: the initial sticking coefficient S 0 is approximately 1% for thermal mole-cules, E i = 0.025 eV, but rises to 90% at E i = 0.9 eV. This findings are at variance with the results of recent density functional theory cal-culations, predicting near unity reaction probability, even at low E i . In an attempt to clar-ify the dynamics of the initial stages of the oxidation process, I investigated the O 2 /Al interaction by means of molecular beam and laser spectrometric techniques (resonantly enhanced multiphoton ionization - REMPI). The results of the present work, coupled to the finding of scanning tunneling microscopy investigations performed by A.J. Komrowski and A.C. Kummel of the University of California, provide compelling evi-dence for the existence of an abstractive pathway for the dissociation of oxygen on alu-minum. The REMPI study also allowed to highlight the dependence of the abstraction coeffi-cient on both the translational and rotational energy of the incoming oxygen molecules.

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Binetti, Marcello: Non-adiabatic reaction pathways in the dissociative adsorption of Oxygen on an Al(111) surface.

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