Chemisorption of CO on Co(0001). Structure and electronic properties

Angle-resolved photoemission with synchrotron radiation, low-energy electron diffraction, and x-ray photoelectron spectroscopy have been combined to study the behavior of chemisorbed CO on the hexagonal Co(0001) surface as a function of coverage, temperature, and CO partial pressure. The band structure was measured for the (√3×√3)R30^∘ (coverage =1/3 monolayer) and the (2√3×2√3)R30^∘ (=7/12 monolayer) phases. The results are compared to tight-binding calculations and show that hybridization effects for the 5σ and 1π bands and orbital mixing are important. The photoemission cross sections (shape resonances) are found to be significantly different for the high- and low-temperature phases.