arXiv 2003.118882020-03-26astro-ph.GAphysics.chem-ph

气相多环芳烃分解产物的红外离子光谱研究

Breakdown products of gaseous polycyclic aromatic hydrocarbons investigated with infrared ion spectroscopy

A. Petrignani, M. Vala, J. R. Eyler, A. G. G. M. Tielens, G. Berden, A. F. G. van der Meer, B. Redlich, J. Oomens

发表信息：: The Astrophysical Journal, 826, 2016, 33
DOI：: 10.3847/0004-637X/826/1/33

摘要：

本文报道了三种不同的三环多环芳烃（PAH），芴（C $_{13}$ H $_{10}$），9，10-二氢菲（C $_{14}$ H $_{12}$）和9，10-二氢蒽（C $_{14}$ H $_{12}$）在电子电离诱导裂解过程中形成的一种常见碎片离子。在傅里叶变换离子回旋共振质谱仪中获得了与$m/z=165$质量隔离的产物离子的红外光谱，该质谱仪的单元被放置在红外自由电子激光的光学腔内，从而提供有效的红外多光子解离所需的高光子注量。发现由三种不同前体产生的$m/z=165$物质的红外光谱相似，表明形成了单一的C-$_{13}$ H $_{9}^+$异构体。使用密度泛函理论（DFT）的理论计算揭示了该片段的身份作为闭壳芴基阳离子。从每个母体前体的芴离子的分解途径提出的DFT计算的基础上。从三种不同的多环芳烃的单一裂解产物的识别支持的概念，存在的共同分解途径的多环芳烃一般，可以帮助理解天文多环芳烃物种的裂解化学。

英文摘要：

We report on a common fragment ion formed during the electron-ionization-induced fragmentation of three different three-ring polycyclic aromatic hydrocarbons (PAHs), fluorene (C$_{13}$H$_{10}$), 9,10-dihydrophenanthrene (C$_{14}$H$_{12}$), and 9,10-dihydroanthracene (C$_{14}$H$_{12}$). The infrared spectra of the mass-isolated product ions with $m/z=165$ were obtained in a Fourier transform ion cyclotron resonance mass spectrometer whose cell was placed inside the optical cavity of an infrared free-electron laser, thus providing the high photon fluence required for efficient infrared multiple-photon dissociation. The infrared spectra of the $m/z=165$ species generated from the three different precursors were found to be similar, suggesting the formation of a single C$_{13}$H$_{9}^+$ isomer. Theoretical calculations using density functional theory (DFT) revealed the fragment's identity as the closed-shell fluorenyl cation. Decomposition pathways from each parent precursor to the fluorenyl ion are proposed on the basis of DFT calculations. The identification of a single fragmentation product from three different PAHs supports the notion of the existence of common decomposition pathways of PAHs in general and can aid in understanding the fragmentation chemistry of astronomical PAH species.

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