Phys.org  April 7, 2023 Hydroxyl radical (OH) is a key oxidant that triggers atmospheric oxidation chemistry in both gas and aqueous phases. The current understanding of its aqueous sources is mainly based on known bulk (photo) chemical processes, uptake from gaseous OH, or related to interfacial O3 and NO3 radical-driven chemistry. An international team of researchers (France, USA – UC Irvine, Israel) has provided experimental evidence that OH radicals are spontaneously produced at the air–water interface of aqueous droplets in the dark and the absence of known precursors, possibly due to the strong electric field that forms at such interfaces. […]