The role of polycyclic aromatic hydrocarbons (PAHs) in the formation of nascent soot particles in flames is well established and yet the detailed mechanisms are still not fully understood. Here we provide experimental evidence of the occurrence of dimerization of PAHs in the gas phase before soot formation in a laminar diffusion methane flame, supporting the hypothesis of stabilization of dimers through the formation of covalent bonds. The main findings of this work derive from the comparative chemical analysis of samples extracted from the gas to soot transition region of a laminar diffusion methane flame, and highlight two different groups of hydrocarbons that coexist in the same mass range, but show distinctly different behavior when processed with statistical analysis. In particular, the identified hydrocarbons are small-to-moderate size PAHs (first group) and their homo- and heterodimers stabilized by the formation of covalent bonds (second group).

多环芳烃 (PAH) 在火焰中新生烟灰颗粒形成中的作用已得到充分证实，但详细机制仍未完全了解。在这里，我们提供了在层流扩散甲烷火焰中烟灰形成之前气相中多环芳烃二聚化发生的实验证据，支持通过形成共价键稳定二聚体的假设。这项工作的主要发现来自于对从层流扩散甲烷火焰的气体到烟灰过渡区提取的样品进行的比较化学分析，并突出了在相同质量范围内共存的两组不同的碳氢化合物，但在以下情况下表现出明显不同的行为经统计分析处理。尤其，