Structure of Chemisorbed CO

The CO chemisorption is molecular at low temperature [207]. At higher temperatures the CO is dissociated. Evidence for the existence of more than one 

The disorder observed below room temperature [383, 427] [429] is caused by the lack of mobility [427]. Just below the dissociation temperature ordering is observed. 

While molecular and dissociated CO have similar X-ray photoelectron spectroscopy spectra, 0(ls) at 531 eV and C(ls) at 285 eV [245, 427, 431], the ultra violet photoelectron spectroscopy [245, 427] and laser Raman [432] spectra are different. 

During sequential adsorption of CO and CO on Fe(lOO), isotopic exchange is observed only among the two strongest bound molecular states [433]. For the catalyst, isotopic scrambling between C O and C 0 is observed at — 33 °C indicating the existence of dissociated CO at these temperatures. There is partial isotropic scrambling between the first and second exposure at - 195 °C [434] and at -78°C [435]. 

For single crystal surfaces the initial enthalpy of chemisorption for CO is —105 kJ/mole on Fe(lOO) by temperature programmed desorption [383], — 96 kJ/mole on Fe(l 10) by temperature programmed desorption [245, 436], —91 kJ/mole by temperature programmed desorption on Fe(l 11) [437], and — 155 kJ/mole by calorimetry on Fe(pc) [438]. 

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An exact interpretation of the basic reasons for the effect of the carrier on the structure of chemisorbed CO cannot yet be advanced. Qualitatively it appears that the alumina makes it easier for the platinum to provide electrons for bonding between the CO and the surface. This is based on a comparison of several possible electronic structures of the chemisorbed CO. The bond between the surface and the carbon of the linear CO could be either a double or a single bond,... 

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