Radical-omics reveals the hydrogen-abstraction pathway of isoprene oxidation

Isoprene is the most abundant biogenic volatile organic compound (BVOC) and has far-reaching impacts on secondary organic aerosol (SOA) formation globally. Its atmospheric oxidation produces diverse isomeric radicals that drive subsequent chain propagation and mechanistic branching. However, high-throughput experimental characterization of these isomeric-resolved radicals remains unavailable, leaving critical gaps in the underlying molecular mechanisms. Here we establish a radical-omics approach for isomer-specific identification and detection of hundreds of radical species generated during VOCs oxidation. Applied to OH-initiated isoprene oxidation, this method enables experimental quantification of four OH-added allylic radicals and determination of their branching ratios. We further found hydrogen-abstraction to be an unexpectedly important pathway, contributing up to 8.78 ± 3.96% of total branching. Incorporating the updated mechanism into a global chemical transport model shows that this pathway contributes up to 13.5% of isoprene-derived low-volatility SOA over tropical rainforests. These results provide an experimental foundation for radical screening and targeted mechanistic validation, revealing hidden pathways in complex atmospheric conditions.