Reactions of Atoms with Magnesium Oxide Surfaces Studied in a Flow System by ESR‐Spectroscopy

Energy transfer from excited metastable He‐ and Ar‐atoms to MgO surfaces as well as reactions of atomic hydrogen, oxygen and nitrogen respectively with these surfaces in a flow system produce paramagnetic centers which are detected in situ by ESR. The signals observed are attributed to S‐ and S H ‐centers as well as to O ‐radicals and to V b ‐type centers of clustered O ‐ ‐radicals. The reaction of S‐centers with N 2 O‐gas yielding O was observed. Mechanisms for the interaction of excited rare gas atoms and of H‐ O‐ and N‐atoms with the defect oxide surface are discussed. At high microwave power the ESR‐signal of the S‐center appears in emission. Fast valence change processes of Mn‐ions in MgO were observed on interaction with H‐ or O‐atoms.