Kinetic Model Simulations.

The behaviors of RO₂, HOM, OrgN, and C_16–20 dimers formed from α-pinene ozonolysis under typical experimental conditions were simulated using the F0AM v3.1 box model (53) employing MCM v3.3.1 (54). The α-pinene oxidation mechanism was updated to include RO₂ autoxidation, as well as HOM and dimer formation based on literature data and experimental results of the present study. Major modifications to MCM v3.3.1 are described in detail in SI Appendix, section S3 and Table S2. Measurement-model comparisons, as described in detail in SI Appendix, section S4, were performed to constrain the kinetic parameters of RO₂ chemistry (SI Appendix, Table S3), which were treated as free fitting parameters in the model.