The Earth¿s climate is strongly influenced by clouds. The oxidative processing of pollutants in clouds affects cloud droplet size and optical properties, important climatic effects. Common cloud pollutants are naturally occurring organic surfactants forming organic films on the droplet. The magnitude of climatic effects depends upon the fate of the organic films following atmospheric oxidation. In this work we will measure the oxidation rate of ozone with mixed films. Specifically:-(a) Does the reaction between ozone and oleic acid initiate radical reactions in the film involving film components unreactive to ozone.(b) Measure the initial loss of oleic acid owing to reaction with ozone in a mixed film (i.e does the oleic acid environment effect the rate of oxidation). (c) Support an STFC/NERC case award student who will be based at ISIS 2008-2009.