Fig. 2.

UPLC/(−)ESI-Q-TOF-MS BPI chromatograms of SOA produced from the O₃-initiated oxidation of β-pinene in the CPOT in the presence and absence of cyclohexane as an OH scavenger (SI Appendix, Table S1, Exps. 7 and 8). Numbers correspond to nominal m/z values of [M−H]⁻ ions; molecular formulas are given in parentheses. (Inset ) Dimers that exhibited a significant decrease in abundance due to cyclohexane addition (Table 1), reported as a percent change relative to the control experiment and precise to <10%. Data for Control and OH Scavenger experiments are normalized to the total organic carbon content of the corresponding SOA samples (SI Appendix, S3.4) and are reported as averages of replicates (n = 3).