Paper SS-TuM5
Photoinduced Electron Transfer Chemistry of CO₂ on Pt(111): Dissociation and Desorption following Å–Scale Molecular Acceleration Towards the Surface

Tuesday, October 21, 2008, 9:20 am, Room 208

Ultraviolet photoinduced electron transfer from a low temperature Pt(111) surface to physically adsorbed CO₂ is shown to lead to acceleration of the newly formed negative ion towards the surface, neutralization, and a high energy collision with the surface that efficiently dissociates (ca. 30%) and desorbs CO₂. The translational energy distributions and angular distributions of photodesorbing CO₂ are compared to those of CO₂ product from the photoreaction between coadsorbed CO and molecular O₂. The similarities of the desorbing CO₂ distributions argue for similar exit channel dynamics following access to configurations near the transition state for CO₂ dissociation/CO oxidation (i.e., configurations at chemisorptive distances from the surface). Consequently, the initially physisorbed CO₂ is accelerated towards the surface following photoinduced electron transfer and can undergo “Antoniewicz bounce” photodesorption dynamics. More interestingly, the initial Å-scale molecular acceleration towards the surface generates molecule/surface collisions at chemically significant energies sufficient to dissociate CO₂.