ADSORPTION OF CARBON-MONOXIDE ON IR(110) INVESTIGATED BY INFRARED REFLECTION-ABSORPTION SPECTROSCOPY

The adsorption of carbon monoxide on the Ir(110) surface at 300 K has been investigated with Fourier transform infrared reflection-absorptio n spectroscopy. A single band was observed that shifted up from a low- coverage value of 2001 cm(-1) to a saturation-coverage limit of 2086 c m(-1). This band is attributed to the carbon-oxygen stretching mode of a molecule adsorbed on top of a surface iridium atom. This frequency shift was separated into a contribution due to dipole-dipole interacti ons and a smaller contribution from chemical effects (d-electron compe tition) by using isotopic substitution. Employing knowledge of the str ucture of the reconstructed Ir(110) surface and temperature-programmed desorption spectra measured at various coverages, an adlayer model is proposed to reconcile a single adsorption site with the temperature-p rogrammed desorption data.