Unveiling the anisotropic behavior of ultrafast electron transfer at the metal/organic interface

Abstract

Ultrafast electron transfer between adsorbed organic molecules and metal substrates is studied. In particular, the dynamics of the active electron in the nitroethylene anion/metal-copper surface system has been followed in real time using a wave packet propagation approach, allowing a rigorous analysis of the decay of molecule-localized electronic resonances. We find that the strong coupling with the metal substrate leads to an extremely short lifetime (~1fs) of the π∗ molecular resonance. Comparison between the free-electron metal, Cu(100), and Cu(111) surfaces demonstrates that the electronic band structure of the substrate and the shape of the decaying molecular orbital lead to a highly marked anisotropy of the metal continuum states populated by resonant electron transfer from the adsorbate. This finding points at possible anisotropy effects in adsorbate–adsorbate interactions and it is of particular importance in molecular self assembly at metal surfaces, thus opening the way to a rational design of hybrid metal/organic interfaces with tailored electronic properties.