Hot-electron-driven charge transfer processes on ${\mathrm{O}}_2/\mathrm{Pt}\mathrm{}\left(111\right)\mathrm{}$ surface probed by ultrafast extreme-ultraviolet pulses

We use ultrafast extreme-ultraviolet photoelectron spectroscopy to directly monitor the electron dynamics and the characteristic valence-band photoelectron spectra associated with a hot-electron mediated surface chemical reaction. By adsorbing molecular oxygen onto a Pt(111) surface and exciting it with an ultrafast laser pulse, charge transfer induced changes in the platinum-oxygen bond were observed on femtosecond time scales. By simultaneously monitoring both the hot-electron distribution at the Fermi edge and the valence-band photoemission spectra, it was determined that the thermalization of the hot-electron gas precedes significant changes in the ${\mathrm{O}}_2/\mathrm{P}\mathrm{t}$ bond.