Direct Observation of Surface Chemistry Using Ultrafast Soft-X-Ray Pulses

We present the first demonstration of the use of ultrafast extreme-ultraviolet pulses to directly monitor a surface chemical reaction on femtosecond time scales. By adsorbing molecular oxygen onto a platinum surface and exciting it with an ultrafast laser pulse, changes in the oxygen-platinum chemical bond on a subpicosecond time scale were observed through changes in the photoelectron spectra. This work demonstrates a powerful new technique for studying reactions of interest in catalysis and for probing changes of local order on surfaces on their fundamental time scales.