Stimulated desorption from CO chemisorbed on Cr(110)

Abstract

Electron stimulated desorption (ESD) experiments using a time-of-flight pulse counting method are reported for molecular CO chemisorbed on the Cr(110) surface at 90 K. Consistent with previous qualitative observations, negligible CO + and O + desorption signals were measured from the α 1CO overlayer which saturates at 1 4 monolayer. For θ CO > 0.25, a terminally-bonded (α 2CO) binding mode is populated in addition to the existing ∝ 1CO binding mode and the ion yield increases sharply. For α 2CO, both O + and CO + ions are observed; the CO + ions desorb with characteristically lower kinetic energies than O + ions. Near saturation coverages of CO(ads), an observed decrease in the O + yield is attributed to adsorbate-adsorbate interactions which reduce the ion desorption probability, as seen in ESD studies of terminally-bonded CO on other metals. These results are considered in the context of two possible models proposed for the α 1CO binding state and related ESD observations for CO chemisorbed on Fe(001) and potassium-promoted Ru(001).