Cross Sections and Nitric Oxide Product State Distributions Resulting from Substrate Mediated Photodissociation of Nitrogen Dioxide Adsorbed on Palladium(111).
UV irradn. of NO₂ adsorbed on a NO satd. Pd(111) surface caused the photodissocn. of NO₂/N₂O₄ and resulted in the desorption of NO mols. The process was studied using excitation energy between 3.5 and 6.4 eV. At 6.4 eV, a cross section of 3 * 10⁻ⁱ⁸ cm² was found. Using laser-induced fluorescence to detect the desorbed NO mols., fully state-resolved data detailing the energy channeling into different degrees of freedom were obtained. Two desorption channels were found, one characterized by nonthermal state populations, and the other, showing accommodation on the surface. The yield of the fast channel showed a marked increase above 4 eV. The slow channel is interpreted as being due to NO mols. which, after formation, undergo a trapping-desorption process. A polarization expt. indicated that the photodissocn. is initiated by excitation of metal electrons rather than direct absorption by the adsorbate.
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