Photoadsorption and photocatalytic processes influencing the composition of the earth's atmosphere. I. Irreversible photoadsorption of Freon-134a on magnesia under conditions simulating atmosphere

It is shown that Freon-134 a (asymmetric tetrafluoroethane) is irreversibly adsorbed on dispersed magnesia under the action of a mild UV radiation with a high quantum yield (6% at λ = 313 nm), but is not adsorbed in the dark. Under pressures of 0.1-10 Pa, the rate of photoadsorption does not depend on the freon pressure. During freon photoadsorption, oxygen anions are probably substituted by fluorine anions. The degree of substitution may exceed 10% of the monolayer capacity. The spectral range of freon photoadsorption is substantially shifted to higher wavelengths (λ < 365 nm) as compared to the absorption of MgO (λ < 178 nm). The spectral dependence of the quantum yield is determined.