Abstract
Abstract A tight-binding Green's function approach is used to describe the bonding of a diatomic molecule to a metallic substrate. The molecule is idealized as a two-level system with an occupied donor orbital and an empty low-lying acceptor level, and the metal as a single half-filled band. The formation of a metastable metal-to-ligand charge transfer state or negative ion resonance after electronic excitation is demonstrated. The lifetime of the negative ion resonance is determined and effective atomic charges and bond orders are computed for both the ground and the excited states. Potential energy curves and the coordinate dependence of the lifetimes are computed by varying the adsorbate–surface distance, and hence the coupling strength between the molecule and the substrate. Based on a truncated Born expansion of the perturbed Green's matrix, an approximate and physically intuitive expression for the negative ion resonance width is derived and numerically justified. Variation of tight-binding parameters other than the molecule–surface coupling allows for the simulation of a broader class of substrates and adsorbates.
Published Version
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