Photoinduced dissociative electron attachment of CH3Br on Pt(111): The role of the local work function

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Abstract
The photoinduced dissociative electron attachment of CH3Br on Pt(111) has been examined by measuring CH3 photofragment translational energy distributions from CH3Br adsorbed on Xe multilayers deposited upon CH3Br covered Pt(111). Subvacuum level, photoexcited substrate electrons produced by 308 nm laser irradiation were found to propagate through the Xe layer where attachment to CH3Br led to fragmentation. A simple model for surface dissociative electron attachment, DEA, was found to quantitatively predict the observed fragmentation dynamics for the CH3Br/Xe/CH3Br/Pt(111) system. The role of the local work function in surface DEA processes was explored by examining the dependence of the photofragment yield upon the thickness of the intermediate Xe layer and the fractional coverage of the Pt(111) bound first layer of CH3Br. Three dimensional variation of the local work function above the substrate was required to account for the observed DEA dynamics.