Polycyclic aromatic hydrocarbons (PAHs) are widely accepted as precursors for soot. Two major pathways of soot nucleation initiated from PAHs are known, namely, physical nucleation of PAHs into stacked clusters and chemical nucleation of PAHs into an aromatic network via cross-linking reactions . Physical nucleation of PAHs is only possible for large PAHs (>667 Da), but these species fail to be observed in experimental studies due to their low concentrations . Chemical nucleation is a process where reactive sites on PAHs are chemically combined to form a stable structure. These reactive sites can be connected by acetylene, which refers to the well-known hydrogen abstraction acetylene addition (HACA) growth mechanism . Another chemical pathway is the formation of a π-bonding network where π-radicals directly react with PAH σ-radicals without the requirement of hydrogen abstraction . These πradicals can be stabilized due to delocalization, also known as long-lived resonantly stabilized radicals (RSRs). The existence of PAH π-radicals in sooting flames has been reported by high-resolution atomic force microscopy (HR-AFM) and photoionization mass spectrometry experiments . The reactivity of different sites on a range of PAH radicals was examined by Martin et al. . They found that σradicals are the most reactive, forming bonds with other radicals. Partially saturated rim-based pentagonal rings were found to form localized π-radicals with high reactivities. The forward rate constants of these radicals are calculated by Menon et al. . The maximum rate was 10 12 cm 3 mol -1 s -1 for aryl-radical recombination, which is still insufficient to trigger the nucleation flux for nanoparticle formation .