An inverse photoemission study of CO overlayers on Ru(0001)

We have examined the properties of several isochromat detectors and selected a Galileo 4800 series channel electron multiplier/CaF 2 combination for use in IPES experiments on clean and CO covered Ru(0001). These experiments, performed at T = 300 K and at an off-normal angle of incidence, showed a bulk, a crystal-induced surface state and an image potential state for clean ruthenium with the image state being suppressed at intermediate CO coverages and re-emerging with the formation of ordered overlayers. Two new features emerge upon CO adsorption. They are attributed to a splitting of the 2π ∗ state into bonding and anti-bonding components.