Chemisorption of CO on tungsten (100): Combined flash desorption and electron stimulated desorption study. II

The chemisorption of CO on W(100) at ~ 100K has been studied using a combination of flash desorption and electron stimulated desorption (ESD) techniques. This is an extension of a similar study made for CO adsorption on W(100) at temperatures in the range 200–300K. As in the 200–300 K CO layer, both α₁-CO and α₂-CO are formed in addition to more strongly bound CO species upon adsorption at ~ 100K; the α-CO states yield CO⁺ and O⁺ respectively upon ESD. At low CO coverages, the α₁ and α₂-CO states are postulated to convert to β-CO or other strongly bound CO species upon heating. At higher CO coverages, α₁-CO converts to α₂-CO upon thermal desorption or electron stimulated desorption. There is evidence for the presence of other weakly-bound states in the low temperature CO layer having low surface concentration at saturation. The ESD behavior of the CO layer coadsorbed with hydrogen on W(100) is reported, and it is found that H(ads) suppresses either the concentration or the ionic cross section for α₁ and α₂-CO states.