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.