In this work, we explore how a certain class of short lived chemicals, called peroxy radicals (RO2) contribute to the formation of air pollution. Peroxy radicals have lots of different chemical reactions available to them, but some of these reactions, especially the ones that can lead to the formation of particulate pollution, are relatively poorly understood. This is because, while these reactions are important in the atmosphere, they often get outcompeted by other reactions in typical laboratory experiments. To isolate and study these uncertain reactions, we use a new experimental approach where we shine UV light on specific chemicals that form RO2 directly without the need for other reactive gasses. This approach lets us specifically focus on those reactions that are least well understood. We use a computer model to help us understand the chemistry we observe and plan our experiments. We use advanced analytical instrumentation to measure the products of these reactions in real time, allowing us to better understand the rates and products of these reactions and how they interact with each other to impact atmospheric composition and air quality.