Inelastic electron tunneling spectroscopy as a probe of electronic coupling at a molecule-metal interface

We introduce inelastic electron tunneling spectroscopy to distinguish between the weak and strong electronic coupling of a bistable molecule to a metal electrode. Ab initio electronic structure calculations demonstrate that the electronic coupling strength is related to the hybridization of molecular orbitals at the interface as evidenced by their energy broadening and shifting to the Fermi level of the metal electrode surface. The hybridization determines the lifetime of the electrons on the molecule, affecting the signal strength in inelastic electron tunneling spectroscopy. We establish this correlation by tuning the electronic coupling strength via an interaction with a scanning tunneling microscope tip, achieving intermediate states between weak and strong coupling.