Conducted at the Paul Scherrer Institut environment chamber, Mass Spectrometers for the CHemical Analysis of Organic aerosolS (MSCHAOS) was a multi-partner venture, funded by the EU ACCENT programme, investigating the use of state-of-the-art mass spectrometers to probe the organic composition of the gas- and aerosol- phase matrices during Secondary Organic Aerosol (SOA) formation, from both anthropogenic and biogenic volatile organic compound (VOC) precursors. During MSCHAOS, we deployed Chemical Ionisation Reaction Time-of-Flight Mass Spectrometry (CIR-TOF-MS) to make detailed measurements of the products of isoprene, alpha-pinene and 1,3,5-trimethyl benzene (1,3,5-TMB) photooxidation. The comprehensive measurements made, lent insight into the complex oxidation mechanisms involved and enabled us to evaluate Master Chemical Mechanism reaction schemes. Highlight findings included the first real-time measurements of high-mass, oxygen-bridged peroxy-bicyclic products of 1,3,5-TMB oxidation.
