Abstract

Chemistry driven by intense ultrafast pulses (femtochemistry) is distinguished from conventional phonon-mediated chemical reactions in that the product yield can be greatly enhanced and more importantly, new chemical reaction pathways can be accessed [1]. In a surface-adsorbate system, non-equilibrium or “hot” electrons created by a femtosecond pulse can drive these reactions[2]; however, direct, time-resolved observation of hot-electron-driven reactions has proven to be difficult. Here, we present time-resolved observations of a hot-electron driven change of adsorbate molecules (O₂) on a metal surface (Pt) from one chemisorbed species to another. The process of time-resolved ultraviolet photoelectron spectroscopy makes it possible to observe both electronic energy relaxation, and structural changes in the surface/adsorbate, on their fundamental, femtosecond timescales.

© 2002 Optical Society of America