A mechanistic understanding of the varying yields of highly oxygenated organic molecules.

Highly oxygenated organic molecules (HOM) play a crucial role in the formation and growth of atmospheric particles, thereby influencing air quality and climate. A comprehensive understanding of HOM formation, particularly an accurate quantification of their yields, is essential to constrain the climate and health impacts of aerosols. Previous studies often reported constant HOM yields as averages, overlooking nuanced changes. Here we revisit several experimental datasets and demonstrate that HOM yields from single volatile organic compounds (VOCs) can vary by more than a factor of 3, depending on numerous parameters affecting peroxy radicals (RO2) autoxidation. Additionally, we propose a concept of RO2 oxidation fraction, which provides a unified explanation for variations in the HOM yields. Our findings indicate that applying the laboratory-derived HOM yields to the interpretation of ambient data may lead to substantial biases, especially when VOC and oxidant concentrations in the laboratory were higher than those in the real atmosphere.