Publication

Abstract

Fullerene thin films are probed by infrared absorption and sum-frequency generation. These techniques together determine the infrared and/or Raman character of adsorbate vibrations. The normally Raman active Ag(2) mode of C60 gains strong infrared activity upon adsorption on Ag(111). This unexpected infrared activity of the mode is shown to result from a dynamic charge transfer occurring between the substrate and the adsorbate. Through K-doping of the monolayer, tuning of the admolecule electronic properties and subsequent control of the interfacial dynamic charge transfer (IDCT) process are obtained. In particular, the predicted concomitant quenching of the IDCT and of the accompanying infrared activity and softening of the Ag(2) mode is observed. A quantitative evaluation of the coupling strength of the Ag(2) vibration to the t1u orbital of C60 is provided.

Author addresses

1. Laboratoire de Spectroscopie Moléculaire de Surface (LASMOS)
   Institute for Studies in Interface Science (ISIS)
   Facultés Universitaires Notre-Dame de la Paix (FUNDP)
   61 Rue de Bruxelles, B-5000 Namur, Belgium



2. Laboratoire pour l'Utilisation du Rayonnement Electromagnétique (LURE)
   Centre National de la Recherche Scientifique (CNRS)
   Bâtiment 209D, F-91405 Orsay, France



3. Also LASIR-CNRS, 2 rue Henry Dunant, F-94320 Thiais, France