Photodissociation and photodesorption of O2 adsorbed on Pd(111)
The dynamics of the UV-photochem. of molecularly adsorbed O on Pd(111) was studied using pulsed laser light at 3.9-6.4 eV photon energy. Photodissocn. to form at. surface O and photodesorption of O2 are the primary processes. The latter is characterized by a translational energy of .apprx.800 K indicating nonthermal desorption. Since the photolytically formed at. O competes with the mol. adsorbate for binding sites some of the latter is displaced. This manifests itself in a conversion process between adsorbate states and in a desorption channel with a translational energy of 120 K indicating accommodation to the surface temp. The cross sections for all processes rise exponentially at 3.9-6.4 eV by a factor of 38.
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