Effect of local geometry on magnetic property of nitric oxide on Au(110)−(1×2)

We investigate the effect of local geometry and environment on the electronic spin of nitric oxide (NO) on Au(110)-($1\ifmmode\times\else\texttimes\fi{}2$) using scanning tunneling microscopy/spectroscopy, density functional theory, and numerical renormalization group calculations. The molecules adsorb on the bridge or on-top sites, and the Kondo resonance is observed only for the latter. This indicates that the local geometry influences the spin state of NO on the surface. The Kondo resonance is accompanied by enhanced satellite peaks due to the interplay with vibrational excitation. In addition, we find that the Kondo resonance appears as a peak or a dip, depending on the local environment of the molecule. The calculations reveal that the NO/Au(110) system is represented by a two-orbital Anderson model, where the $2{\ensuremath{\pi}}^{*}$ orbitals compete for the unpaired electron to host the Kondo resonance. We propose that a subtle interaction between the NO molecules may play a critical role in determining the host of Kondo resonance and, consequently, the spectral shape.