EPR Characterization and Reactivity of Surface-Localized Inorganic Radicals and Radical Ions

The variety of inorganic radicals which are formed at oxide surfaces, emphasizing the importance of the structure-reactivity relationship and adsorbate-surface interaction, were studied. First are surface organic radicals because their large number and particular features require a specific analysis. Identification and characterization of surface radicals are essentially conducted using EPR techniques which provide, on the basis of g, hyperfine, and superhyperfine tensors, a detailed understanding of the radical composition and structure and, in some cases, the nature of the surface adsorption sites. In the bulk of a solid or at its surface, different types of paramagnetic species can be present before and after adsorption of gas-phase molecules. An interesting process involving chlorine dioxide was reported by Raghunathan and Sur, who showed that by EPR, the photoisomerization of CIO2 obtained by UV irradiation after adsorption in cancrinite.