Electron transfer at molecule-metal interfaces: A two-photon photoemission study

Electron transfer between a molecular resonance and a metal surface is a ubiquitous process in many chemical disciplines, ranging from molecular electronics to surface photochemistry. This problem has been probed recently by two-photon photoemission spectroscopy. The first photon excites an electron from an occupied metal state to an unoccupied molecular resonance. Subsequent evolution of the excited electronic wavefunction is probed in energy, momentum, and time domains by the absorption of a second photon, which ionizes the electron for detection. These experiments reveal the important roles of molecule-metal wavefunction mixing, intermolecular band formation, polarization, and localization in interfacial electron transfer.