Abstract
Photochemistry on metal and semiconductor surfaces has been the topic of intensive expertmental and theoretical research in recent years, both due to the fascinating physics involved and due to the application to surface processing and catalysis. The observation’ of hot translational and internal energy distributions, anisotropic desorbate angular distributions, pronounced isotope effects and marked dependence of the product energy on the incident wavelength suggests predominance of a substrate-mediated mechanism, involving photoexcitation of substrate electrons which subsequently are inelastically scattered by the adsorbate via a transient, electronically- excited or negative ion state. The inelastic scattering event provides a mechanism for redistributing the electron energy into the molecular degrees of freedom. If the energy placed in the center-of-mass translational motion exceeds the relevant bond energy, enhanced desorption (with respect to thermal) may occur. Similarly, channeling of the electronic excitation into internal adsorbate modes may result in dissociation or in a surface reaction.
© 1998 Optical Society of America
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