Spatially inhomogeneous inelastic electron tunneling in oxygen-ethylene complexes on Ag(110) resolved with a scanning tunneling microscope

Inelastic electron-tunneling spectroscopy and microscopy with a scanning tunneling microscope revealed two vibrational modes of O-2 in single O-2-C2H4 complexes adsorbed on a Ag(110) surface at 13 K, showing both increased and decreased ac conductance. While both modes exhibit spatial variations in the intensity, the lower energy mode shows unexpected changes in the sign and lineshape of the peak. The observed spatial variations in the inelastic electron-tunneling signals may be induced by the broken symmetry of the O-2 due to the asymmetrically coadsorbed C2H4 and strong localization in the coupling between the vibrational motion and the electronic molecular orbitals.