研究领域

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Kinetics and photochemistry

Terry’s research is directed towards a detailed understanding of atmospheric free-radical chemistry. Radicals initiate the oxidative removal of atmospheric organics, a vast quantity and variety of which is emitted by vegetation and human activity. Understanding radical chemistry is crucial to assess the impact of emissions on air quality, chemistry and climate, and to confidently predict future trends. In laboratory-based experiments we study the key reactions controlling radical initiation, propagation and termination. A variety of gas-phase kinetic techniques are employed, including laser photolysis, fast-flow systems, and environmental chambers. The goal here is to determine physical chemistry parameters such as rate or equilibrium coefficients, product yields and photolysis quantum yields. These parameters are required to calculate atmospheric lifetimes for pollutants and, more generally, to describe photochemical reactions in models of the atmosphere. Recently the focus has been on the search for radical recycling routes within clean-air organic oxidation mechanisms. We are developing new field instruments for studying free-radical kinetics in real air. Atmospheric radicals are often short-lived and consequently present at low concentrations. Whilst this makes direct monitoring difficult, we can conduct kinetic experiments in the field to determine total loss rates or lifetimes for atmospheric radicals. Lifetimes are crucial for calculating radical budgets, provide a useful test of model reliability, and may reveal the presence of hitherto unidentified organics in the air.