DFT Study on Interstellar PAH Molecules with Aliphatic Side Groups
DFT Study on Interstellar PAH Molecules with Aliphatic Side Groups
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DOI：
10.3847/1538-4357/ab733a
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发表时间：
2020-03
期刊：
影响因子：
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通讯作者：
M. Buragohain;A. Pathak;I. Sakon;T. Onaka
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文献类型：
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作者：
M. Buragohain;A. Pathak;I. Sakon;T. Onaka
多环芳烃（PAH）分子在3.3、6.2、7.7、8.6、11.2和12.7 μm处具有明显的发射特征，而在3-20 μm区域具有较弱的混合特征。相对较弱的3.4 μm发射特征被归因于具有作为载体的脂肪族来源。带有脂肪族官能团的多环芳烃是3.4 μm发射带的潜在候选载流子之一，但其归属仍是一个谜。在这项工作中，我们采用密度泛函理论计算的对称和紧凑的PAH分子，晕苯（C24 H12）与脂肪族侧基研究任何光谱的相似性与观察到的特征在3-4 μm。本研究中考虑的侧基是−H（氢化）、− CH 3（甲基）、− CH 2-CH 3（乙基）和−CH= CH 2（乙烯基）官能团。考虑到多环芳烃中可能存在氘（D），我们还将D引入脂肪族侧基以研究光谱行为。我们提出了一个详细的分析，这些分子的红外光谱，并讨论可能的天体物理意义。
Polycyclic aromatic hydrocarbon (PAH) molecules have been long adjudged to contribute to the frequently detected distinct emission features at 3.3, 6.2, 7.7, 8.6, 11.2, and 12.7 μm with weaker and blended features distributed in the 3–20 μm region. The comparatively weaker 3.4 μm emission feature has been attributed to have an aliphatic origin as carrier. PAH with an aliphatic functional group attached to it is one of the proposed potential candidate carriers for the 3.4 μm emission band, however, the assignment of carrier is still enigmatic. In this work, we employ density functional theory calculation on a symmetric and compact PAH molecule; coronene (C24H12) with aliphatic side group to investigate any spectral similarities with observed features at 3–4 μm. The side groups considered in this study are −H (hydrogenated), −CH3 (methyl), −CH2–CH3 (ethyl), and −CH=CH2 (vinyl) functional groups. Considering the possible presence of deuterium (D) in PAHs, we also include D in the aliphatic side group to study the spectral behavior. We present a detailed analysis of the IR spectra of these molecules and discuss possible astrophysical implications.