Nitrous oxide (N 2 O), with its self‐pressurizing capability, strong oxidizing potential, and exothermic decomposition, is considered a promising green propellant oxidizer. However, when combined with hydrocarbon fuels, the concurrent formation of soot and polycyclic aromatic hydrocarbons (PAHs) remains a major challenge for propulsion efficiency and emission control. This study aims to elucidate the synergistic effects of N 2 O exothermic decomposition and its enhanced oxidizing potential on the transition from PAHs to soot particles using dual‐wavelength laser diagnostics. Primary soot was characterized using Laser‐Induced Incandescence (LII) at 1064 nm, while incipient soot and PAHs were probed with 532 nm excitation. Ethylene inverse diffusion flames (IDFs) were investigated under two oxidizer conditions: pure N 2 O and a decomposition‐equivalent mixture (67% N 2 /33% O 2 ). Results show that N 2 O decomposition significantly accelerates the precursor maturation process, producing up to tenfold higher LII signals with lifetimes over 130 ns, compared to less than 80 ns for O 2 /N 2 flames. The saturation fluence under N 2 O was as low as 0.26 J/cm 2 , lower than 0.48–0.59 J/cm 2 for O 2 /N 2 . Furthermore, the findings reveal a unique interaction: N 2 O–derived thermal effects dominate soot growth at moderate oxidizer‐to‐fuel ratios ( R = 2–6), promoting distinct soot morphology characterized by compact agglomerates rather than the typical chain‐like structures observed in O 2 /N 2 flames. Conversely, oxygen‐enriched effects from N 2 O enhance oxidative consumption at higher ratios ( R ≥ 5), ultimately limiting soot accumulation.
Lin et al. (Thu,) studied this question.