Exciton dynamics at molecule-metal interfaces:: C60/Au(111) -: art. no. 045441

Time-resolved two-photon photoemission spectroscopy is used to probe the energetics and dynamics of electronically excited states in epitaxial C-60 films on a single-crystal Au(111) surface. These measurements reveal a rich variety of excited states corresponding to excitons in C-60, charge transfer resonances at the metal-molecule interface, and image resonances on the surface. The lifetimes of excitons depend on the thickness of the C-60 film over a broad range; for the Frenkel exciton involving LUMO+1, the transient lifetime decreases from similar to 350 fs for film thickness > 30 monolayers to 80 fs at 2 monolayers. The long distance dependence is interpreted as due to the direct coupling between the electronic exciton band in C-60 and substrate metal bands.