A theoretical model was proposed for the description of the kinetics of isotopic O exchange between the gas, and oxides with sub-surface regions which differed from the bulk with regard to the rate of O transfer. Exact solutions were derived which were valid for an arbitrary ratio of the exchange and diffusion rates. These described the time dependence of the total 18O tracer concentration and of 16O16O, 18O16O and 18O18O molecular concentrations. They made it possible to analyze the contributions to kinetics which arose from various types of exchange.

A.N.Ezin, V.I.Tsidilkovski, E.K.Kurumchin: Solid State Ionics, 1996, 84[1-2], 105-12