超越理想化的多环芳烃：激波合成产生的碳链缺陷的红外特征
Beyond Idealized PAHs: Infrared Signatures of Carbon-Chain Defects from Shock Synthesis
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中文总结 AI 辅助
本研究结合模拟与观测，发现激波合成的缺陷PAHs的红外特征可解释天文观测中的特定谱带，为星际介质中存在这类缺陷PAHs提供了观测依据。
中文摘要 AI 辅助
多环芳烃（PAHs）被广泛认为是芳香红外带（AIBs）的载体，但大多数光谱模型依赖理想化结构，无法捕捉星际PAHs形成的高能环境。本研究调查了激波条件下形成的PAHs的红外（IR）特征，探究产生的缺陷结构是否能解释标准理想化模型无法预测的观测特征。我们将PAHs形成的两阶段反应分子动力学模拟（涉及凝聚和激波处理）与密度泛函理论光谱计算相结合，并将理论结果与詹姆斯·韦布空间望远镜（JWST）对NGC 7023和MRK 1066的观测结果进行比较。激波处理产生的PAHs具有类富勒烯碳骨架和线性碳链附属结构，这些结构缺陷产生了独特的红外特征，包括在4.6-5.5微米处出现理想化PAHs不存在的显著碳链伸缩特征，以及在14.5-20微米范围内显著增强的面外骨架模式。我们的发现将NGC 7023和MRK 1066中观测到的5.2微米带归因于碳链振动，15-18微米发射归因于弯曲骨架模式，为星际介质中普遍存在激波形成的缺陷PAHs提供了观测支持。
英文摘要
Polycyclic aromatic hydrocarbons (PAHs) are widely recognized as carriers of the aromatic infrared bands (AIBs). However, most spectral models rely on idealized structures that fail to capture the energetic environments of interstellar PAH formation. This work investigates the infrared (IR) signatures of PAHs formed under shock conditions and explores whether produced defective structures can explain observational features unpredicted by standard, idealized models. We combine two-stage reactive molecular dynamics simulations of PAH formation via condensation and shock processing with density functional theory spectral calculations, and compare our theoretical results with James Webb Space Telescope (JWST) observations of NGC 7023 and MRK 1066. Shock processing produces PAHs featuring fullerene-like carbon skeletons and linear carbon-chain attachments. These structural defects yield distinct IR signatures, including prominent carbon-chain stretching features at 4.6-5.5 micron that is absent in ideal PAHs, and significantly enhanced out-of-plane skeletal modes in the 14.5-20 micron regime. Our findings attribute the observed 5.2 micron band in NGC 7023 and MRK 1066 to carbon-chain vibrations and the 15-18 micron emission to curved skeletal modes, providing observational support for the prevalence of defective, shock-formed PAHs in the interstellar medium.
