E.P.R. studies of the structure, mobility and reactivity of CO –2 and CO –3 species adsorbed on MgO

Abstract

F⁺-centres trapped in u.v. irradiated MgO react with CO₂ to yield CO^–₂ radicals. The mobility and the structure of the adsorbed CO^–₂ radicals depend on the reaction temperature. Besides the usual CO^–₂ radical a rotating CO^–₂ radical was observed, being more reactive towards N₂O to give the CO^–₃ radical with g⊥= 2.014 and g∥= 2.006 which exhibited a flexional behaviour. It was converted into the more conventional CO^–₃ species rigidly held on the surface of MgO, and characterized by g∥≃ 2.018 and g⊥= 2.006. In the process of this conversion a mobile CO^–₃ radical could be detected, it exhibited an isotropic g-tensor at g= 2.012 due to motional averaging.