Femtosecond dynamics of chemical reactions at surfaces

One of the major goals in physical chemistry is to obtain a microscopic und erstanding of chemical reactions. Recent developments in femtosecond laser techniques provide the opportunity to resolve the timescale of elementary s teps of chemical reactions at surfaces. This is exemplified for the femtose cond laser-induced oxidation of CO on Ru(001). Among other adsorbate-specif ic probes vibrational sum-frequency generation spectroscopy offers the poss ibility to monitor adsorbates or reaction intermediates directly at the sur face. Recently, we have employed this technique to investigate the dynamics of the GO-stretch vibration of CO adsorbed on Ru(001) after optical excita tion leading to CO desorption.