IAS Distinguished Lecture - Radical Chemistry Across Interfaces

Abstract
The chemistry of our atmosphere is shaped not only by reactions in the gas phase but also by processes at interfaces that control reactivity in unexpected ways. Radicals such as OH, HO₂, and chlorine, long recognized as central to ozone depletion and oxidative balance, behave differently at the surfaces of cloud droplets, aerosols, and other condensed phases. Interfaces can align radicals, lower barriers, and accelerate reactions by orders of magnitude, producing pathways absent in the gas phase. These effects provide explanations for unresolved problems ranging from the efficiency of sulfur oxidation and acid rain formation to the persistence and recycling of chlorine in the stratosphere. By integrating computational modeling with experimental observations, the speaker reveals a consistent picture: not all chemistry in the atmosphere is gas-driven, interfacial chemistry is not peripheral but fundamental to atmospheric processes. Recognizing this interfacial control reshapes how we understand the chemical resilience and vulnerability of Earth’s atmosphere.