The adsorption of CO on Rh(100): reflection absorption infrared spectroscopy, low energy electron diffraction, and thermal desorption spectroscopy

The adsorption of CO on Rh(100) has been investigated as a function of temp. and CO pressure, with reflection absorption IR spectroscopy (RAIRA), LEED, and thermal desorption spectroscopy (TDS). At low coverages, most CO adsorbs linearly, up to 0.5 monolayers (ML), where a c(2*2) LEED pattern is obsd. The satn. coverage at 300 K is 0.75 ML, assocd. with p(4?2*?2)R45 Deg LEED pattern, and adsorption of CO in at least three states, namely two linear modes and one bridged mode. At temps. well below 300 K and relatively high exposures, CO is compressed into a dense hexagonal overlayer structure with a c(6*2) LEED pattern and a satn. coverage of 0.83 ML, in which the majority of the CO is bonded linearly. The activation energy of desorption for CO from Rh(100) in the limit of zero coverage is 131 +- 4 kJ/mol and the preexponential factor is (4 +- 3)*1016 s-1. We compare our results with the literature of CO on Rh(100), which shows contradictory results on the vibrational spectra, LEED structures, and satn. coverages of CO. [on SciFinder (R)]