In our recent contribution, we have used DFT calculations and high resolution XPS spectroscopy to identify a critical surface intermediate (surface oxametallacycle), involved in ethylene epoxidation on silver:
S. Linic, H. Piao, K. Adib, M. A. Barteau: “Ethylene Epoxidation on Ag: Identification of the Crucial Surface Intermediate by Experimental and Theoretical Investigation of its Electronic Structure", in press, Angewandte Chemie International Edition.

Ethylene epoxidation on silver has been practiced for about 70 years commercially. It is among the most important heterogeneous catalytic processes. The mechanism of elementary steps involved in this reaction has been unknown and subject to vigorous scientific debate. Difficulties in identifying elementary steps of this process are associated with very illusive surface intermediates that are involved in the catalytic cycle. We have used high resolution XPS and DFT to identify a surface intermediate that reacts to form ethylene oxide (EO) on Ag(111) during its thermal reaction and desorption. The relevant intermediate was formed on the surface in activated adsorption of EO. It appears that this intermediate represents the missing link in our understanding of ethylene epoxidation on silver. To unlock the structure of this critical intermediate we have performed high-resolution XPS experiments, measuring its electronic structure, and have compared this spectrum with DFT computed electronic spectrum of a surface oxametallacycle. The agreement between experiment and theory suggest that this illusive surface intermediate is the surface oxametallacycle. This work represents and example of how experiment and theory can be used to produce important information regarding mechanisms of various processes for which elementary step mechanisms are lacking. (For more see the publication)