ESR‐Study of the Interaction of Oxygen Atoms with Clean Titanium Dioxide Surfaces

Pure titanium dioxide, rutile, with well developed crystal faces was heated after pretreatment with oxygen in an ultrahigh vacuum system (p < 10−8 Torr) up to 1000°C. None of the ESR‐signals were observed reported in the literature for less rigorously cleaned high surface area samples. This finding is discussed on the basis of the thermal disorder equilibrium. Reactions with oxygen atoms resulted in the formation of an adsorbed O2−‐radical. This radical species occurs only after a few reaction steps for which a mechanism is discussed. Changes of the electronic energy levels on adsorption of the O2−‐radical are evaluated from the g‐tensor components (g1 = 2.019, g2 = 2.009, g3 = 2.003).