Wavelength dependence of the photochemistry of molecular oxygen on palladium(111) and the role of hot electron cascades.
The photochem. of O2 adsorbed on Pd(111) has been studied as a function of the energy of the exciting photons in the range of hn = 3.9-6.4 eV. The obtained data are reproduced by a proposed kinetic model considering photostimulated desorption and dissocn., whereby the latter gives rise to addnl. displacement processes. This modeling yields rate consts. and, hence, cross sections for the resp. processes. It is found that the cross sections for all processes rise exponentially with photon energy. This result motivates a study of the distribution of hot electrons generated by laser irradn., and its decay via electron-hole pair scattering events resulting in a broad secondary electron distribution. The energetic and spatial distribution of these electrons is calcd. The probability for these electrons to tunnel into an adsorbate affinity level is modeled and compared to the obsd. photo cross sections.
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