Sulfur Adsorption on Ni(100) and Its Effect on CO Chemisorption. II. UPS (Ultraviolet Photoelectron Spectroscopies) and XPS (X-Ray Photoelectron Spectroscopies) Results

摘要

The adsorption of CO on sulfur-predosed Ni(100) at 95 K was studied using ultraviolet and X-ray photoelectron spectroscopies. For sulfur coverages below 0.22 ML, CO (beta 2 and alpha) adsorbed predominantly on regions of bare Ni, with alpha induced by repulsive CO-CO interactions. For theta s > or = 0.22, a and beta 1 CO adsorbed predominantly within the sulfur domains, and exhibited a reduciton in Ni-CKO backbonding. By theta s = 0.40 a weakly-bound CO state formed (denoted here as sigma). The close association of sigma CO with sulfur resulted in greatly reduced (or non-existent) backbonding and poor final state relaxation from the metal.