Dissociative chemisorption and localized oxidation states at titanium surfaces

Dissociative chemisorption of carbon monoxide and nitric oxide is shown to result in the formation of discrete localised oxidation states of titanium; Ti²⁺ with CO and Ti²⁺ and Ti³⁺ with NO. The results are compared with dioxygen (Ti²⁺, Ti³⁺ and Ti⁴⁺). A correlation is shown to exist between the extent of dissociative chemisorption i.e. overlayer growth and the emergence in a step-wise manner of Ti²⁺, Ti³⁺ and Ti⁴⁺. Attention is drawn to the significance of the Madelung energy in determining the oxidation states generated within the overlayer by this molecule-specific process.