We propose to study the two unsaturated surfactant palmitoleic acid (POA) and oleic acid (OA) and three binary mixtures (1:1) stearic acid (SA)/OA, SA/POA and OA/POA exposed to NO3. By using neutron reflection and simultaneous infra-red spectroscopy we want to study decay kinetics in real time and we aim to obtain mixed rate coefficients for POA and OA in presence of SA, as well as for POA and OA in presence of each other. These surfactants are recognized to be among the most abundant unsaturated surfactants in the atmosphere and very likely alter properties of aerosols that are of key importance for health and climate. The transformation of primary organic aerosols into oxidised aerosols is poorly understood, in particular if occurring at the aerosol surface at night. While much early work has focused on bulk processes, we aim to focus on surface reactions.