To examine the evolution processes of the nitrogen-containing polycyclic aromatic hydrocarbon (PAH) molecules occurring in interstellar environments, in this work we focus on the formation of large covalently bonded N-substituted polyaromatic species and their photochemistry behaviour in the gas phase. The experimental results show large PANH (e.g. DC/acridine and DC/phenazine) cluster cations formed in a chemical reaction between large PAH (e.g. dicoronylene, DC, C₄₈H₂₀) cations and small PANHs (e.g. acridine, C₁₃H₉N, or phenazine, C₁₂H₈N₂) by gas-phase condensation through ion–molecule reactions. With laser irradiation, PANH cluster cations are involved in a complex photofragmentation process (e.g. dehydrogenation, HCN/CN, C₂ or N₂ units lost) and then form large PANH/PAH or multiple dehydrogenated molecules; in particular, the dehydrogenation of PANH clusters provides a possible way to synthesize large nitrogen-containing graphene species (e.g. C₅₉N⁺ and C₆₁N⁺). Also, we perform quantum-theoretical calculations on the formation and photochemistry of DC/acridine and DC/phenazine cluster cations: two types of molecular cluster are considered (C–C and C–N bond type) and the formation pathway and dissociation energy for each isomer are determined. The experimental and theoretical findings obtained give a general molecular growth pathway toward all-benzenoid aromatic species with size (> 60 C atoms) in the astrophysically relevant range, during a ground-up formation process, and offer understanding of the nitrogen element effect on their chemical-evolutionary behaviour. Also, studies of DC/acridine and DC/phenazine clusters (89–112 atoms, ∼2 nm in size) offer a feasible means of explanation for the formation of nanoscale dust grains (nitrogen element included) in space.

中文翻译：

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气相中共价键合的多环芳族氮杂环（PANH）团簇的实验室形成和光化学

为了检查星际环境中含氮多环芳烃（PAH）分子的演化过程，在这项工作中，我们着重于大型共价键合N-取代的多芳族物质的形成及其在气相中的光化学行为。实验结果表明，在大PAH（例如，二亚二甲苯基，DC，C ₄₈ H ₂₀）阳离子与小的PANH（例如eg啶，C ₁₃ H ₉ N ）之间的化学反应中形成了较大的PANH（例如DC / ac啶和DC /吩嗪）簇阳离子或吩嗪，C ₁₂ H ₈ N ₂）是通过离子分子反应通过气相冷凝而产生的。在激光辐照下，PANH簇阳离子参与复杂的光碎裂过程（例如脱氢，HCN / CN，C ₂或N ₂单元损失），然后形成大的PANH / PAH或多个脱氢分子。特别是PANH簇的脱氢为合成大型含氮石墨烯物种（例如C ₅₉ N ⁺和C ₆₁ N ⁺）。另外，我们对DC / ac啶和DC /吩嗪簇阳离子的形成和光化学进行量子理论计算：考虑了两种类型的分子簇（CC和CN键型）以及形成途径和离解能确定每种异构体。获得的实验和理论发现在地面形成过程中提供了通往天体相关范围内尺寸（> 60 C原子）的所有苯系芳族物质的一般分子生长途径，并提供了氮元素对其影响的理解化学进化行为。同样，对DC / ac啶和DC /吩嗪簇（89-112个原子，大小约为2 nm）的研究提供了一种解释空间中纳米级尘埃颗粒（包括氮元素）形成的可行方法。