The adsorption behavior of single CO molecules at 4 K bound to Au adatoms on a Ag(001) metal surface is studied with scanning tunneling microscopy (STM) and inelastic electron tunneling spectroscopy (IETS). In contrast to earlier observations two different binding configurations are observed—one on top of a Au adatom and the other one adsorbed laterally to Au on Ag(001). Moreover, IETS reveals different low-energy vibrational energies for the two binding sites as compared to the one for a single CO molecule bound to Ag(001). Density functional theory (DFT) calculations of the adsorption energies, the diffusion barriers, and the vibrational frequencies of the CO molecule on the different binding sites rationalize the experimental findings.

用扫描隧道显微镜（STM）和非弹性电子隧道光谱法（IETS）研究了单个CO分子在4K下与Ag（001）金属表面上的Au原子结合的吸附行为。与早期的观察结果相反，观察到两种不同的结合构型-一种在Au吸附原子的顶部，另一种横向吸附在Ag（001）上的Au上。此外，与结合到Ag（001）上的单个CO分子的IETS相比，IETS揭示了两个结合位点的低能振动能不同。密度泛函理论（DFT）计算不同结合位点上CO分子的吸附能，扩散势垒和振动频率可以合理化实验结果。