Surface femtochemistry: Ultrafast reaction dynamics driven by hot electron mediated reaction pathways

Fundamental insights into the ultrafast dynamics of energy transfer processes at surfaces are of central importance for a microscopic understanding of chemical reactions at solid surfaces, e.g. in heterogeneous catalysis. The detailed investigation of the rates and pathways of energy flow in the adsorbate-substrate system as well as the chemical dynamics has become possible utilizing intense femtosecond laser pulses. Surprisingly, the strong non-equilibrium situation that arises upon irradiation with these pulses results in a new reaction channel caused by hot electron excitation for a number of systems investigated. This electron-mediated reaction mechanism is exemplified here for the model reaction H-ad + H-ad –> H-2,g on Ru(001) and discussed in the broader context of other simple reactions such as the formation of H2O, CO2 and the CO desorption on the same surface