Energy transfer in oxides. Part 1.—Adsorption of oxygen on magnesium oxide during γ-irradiation
- 1 January 1971
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Transactions of the Faraday Society
- Vol. 67, 1164-1182
- https://doi.org/10.1039/tf9716701164
Abstract
The γ-induced adsorption of oxygen on MgO has been shown to involve an energy transfer mechanism between the bulk and surface of each crystallite. In pure MgO, ionization events which occur within a subsurface region of effective depth ∼90 Å release electrons for the adsorption of oxygen as O– 2 at the surface. In manganese-doped MgO this effective depth is less and the positive holes are trapped at Mn2+ ions which lie within 40 Å of the surface. The initial GT values for oxygen adsorption thus depend on particle size and impurity content and are in the range 1–10. The adsorbed O– 2 ion has been identified by electron spin resonance and this species has been shown to possess an optical absorption in the reflectance spectrum at 2.9 eV, which is possibly due to the 2Πg–2Δu transition. A combination of e.s.r., reflectance and desorption studies during annealing indicates the decrease in the stability of the O– 2 ion with adsorbed coverage.Keywords
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