INFRARED SPECTRA OF ORDERED AND DISORDERED OVERLAYERS ON METALS : CARBON MONOXIDE ON A PLATINUM(111) SINGLE CRYSTAL SURFACE

Abstract

The adsorption of CO on a Pt(111) single crystal surface has been studied by infrared reflection-absorption spectroscopy and surface potential measurements. The surface potential is positive, and after first increasing with coverage it passes through a maximum value and decreases to zero at saturation. The maximum value is temperature dependent, falling from 0.36 V at 80 K to 0.19 V at 500 K, an effect attributed to thermal disordering of the overlayer. Infrared spectra show a single, coverage-dependent band in the range 2 065-2 101 cm-1. The growth of the band at 80 K with increasing coverage differs from that at 295 K. These effects are discussed in relation to the overlayer structure