Abstract
The metal-molecule stretch vibrational mode of CO chemisorbed in the c(4×2) structure on a Pt(111) surface at 100 K has been studied using infrared spectroscopy. For the bridge-bonded molecules the infrared absorption spectra reveal a doublet structure, which is assigned to a Fermi-resonance between the stretch mode and a combination of parallel, dipole-forbidden vibrational modes. Furthermore, no so-called antiabsorption connected to the frustrated rotation is detected, in contrast to what is found on close-packed copper surfaces.