This paper provides experimental evidence for the chemical structures of aliphatically substituted and bridged polycyclic aromatic hydrocarbon (PAH) species in gas-physe combustion environments. The identification of these single- and multicore aromatic species, which have been hypothesized to be important in PAH growth and soot nucleation, was made possible through a combination of sampling gaseous constituents from an atmospheric pressure inverse coflow diffusion flame of ethylene and high-resolution tandem mass spectrometry (MS–MS). In these experiments, the flame-sampled components were ionized using a continuous VUV lamp at 10.0 eV and the ions were subsequently fragmented through collisions with Ar atoms in a collision-induced dissociation (CID) process. The resulting fragment ions, which were separated using a reflectron time-of-flight mass spectrometer, were used to extract structural information about the sampled aromatic compounds. The high-resolution mass spectra revealed the presence of alkylated single-core aromatic compounds and the fragment ions that were observed correspond to the loss of saturated and unsaturated units containing up to a total of 6 carbon atoms. Furthermore, the aromatic structures that form the foundational building blocks of the larger PAHs were identified to be smaller single-ring and pericondensed aromatic species with repetitive structural features. For demonstrative purposes, details are provided for the CID of molecular ions at masses 202 and 434. Insights into the role of the aliphatically substituted and bridged aromatics in the reaction network of PAH growth chemistry were obtained from spatially resolved measurements of the flame. The experimental results are consistent with a growth mechanism in which alkylated aromatics are oxidized to form pericondensed ring structures or react and recombine with other aromatics to form larger, potentially three-dimensional, aliphatically bridged multicore aromatic hydrocarbons.

中文翻译：

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大气采样高分辨率串联质谱法检测烟s火焰中的桥联多核多环芳烃

本文为在气相燃烧环境中脂族取代和桥接的多环芳烃（PAH）物种的化学结构提供了实验证据。这些单核和多核芳族物质的鉴定被认为对PAH的生长和烟灰成核很重要，这是通过结合乙烯的大气压逆同流扩散火焰和高分辨率串联采样气态成分而实现的质谱（MS–MS）。在这些实验中，使用连续VUV灯在10.0 eV下对火焰采样的组件进行电离，然后通过与离子的碰撞在碰撞诱导解离（CID）过程中将离子破碎。产生的碎片离子 用反射电子飞行时间质谱仪分离的样品被用于提取有关采样的芳族化合物的结构信息。高分辨率质谱揭示了烷基化单核芳族化合物的存在，观察到的碎片离子对应于最多包含6个碳原子的饱和和不饱和单元的损失。此外，形成较大PAH的基础结构单元的芳族结构被鉴定为具有重复结构特征的较小的单环和增稠芳族物种。出于说明目的，提供了质量202和434的分子离子CID的详细信息。通过火焰的空间分辨测量，可以了解脂族取代和桥连的芳族化合物在PAH生长化学反应网络中的作用。实验结果与其中烷基化的芳族化合物被氧化形成过稠环结构或与其他芳族化合物反应并重新结合以形成更大的，可能是三维的脂族桥连的多核芳族烃的生长机理一致。