Effect of Film Oxidation on Hygroscopic Behaviour and Surface Structural Changes during Ozonolysis of Thin-Film Fatty Acid Aerosol Proxies

Further to a recent rapid access INTER beamtime where we obtained very promising results, we propose a neutron reflectometry (NR) experiment on spin-coated thin films of self-assembled fatty acids on Si wafers as proxies for atmospheric aerosols. We aim (i) to observe differences in hygroscopic behaviour between pristine and oxidised films of our d-oleic acid/sodium oleate mixture, used as an atmospheric aerosol thin film proxy, and (ii) to characterise surface structure changes during oxidation by ozone. We have shown that we can control the film thickness by spin-coating films at different spin speeds and solution concentrations. These experiments are a key contribution to a wider study involving Diamond Lightsource on the effect of organic film thickness and structure on ozonolysis reaction kinetics and the effect of oxidation on hygroscopic behaviour.