Schleier Domenik, Kamer Jerry, Jiao Andy, Schneider Grégory F, Linnartz Harold, Bouwman Jordy
Laboratory for Astrophysics, Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands.
Lehrstuhl Technische Thermodynamik, Fakultät für Maschinenbau, Universität Paderborn, Warburger Str. 100, 33098 Paderborn, Germany.
Phys Chem Chem Phys. 2024 May 29;26(21):15547-15558. doi: 10.1039/d4cp01387e.
Polycyclic aromatic nitrogen heterocycles (PANHs) are present in various astronomical environments where they are subjected to intense radiation. Their photodissociation pathways give crucial insights into the cycle of matter in the universe, yet so far only the dissociation characteristics of few PANHs have been investigated. Moreover, most experiments use single photon techniques that only reveal the initial dissociation step, and are thus unsuited to replicate astronomical environments and timescales. In this work, we use the Instrument for the Photodynamics of PAHs (i-PoP) at the Laboratory for Astrophysics to simulate the interstellar photodissociation of a model PANH, cationic triazacoronene (TAC˙, CHN). Comparing the observed fragments to similar PAHs such as the isoelectronic coronene can give mechanistic insight into PAH dissociation. For coronene the major photodissociation products were found to be CH, C, and C. In contrast, fragmentation in TAC˙ is initiated by up to three HCN losses often in combination with H- or H losses. In the lower mass region, the fragments show similarities to comparable PAHs like coronene, but for TAC˙ the inclusion of nitrogen atoms into the ionic fragments in the form of (di)cyanopolyynes is also observed. These nitrogen-containing species may be important tracers of regions in interstellar space where interstellar PANHs are being photodissociated.
多环芳族氮杂环（PANHs）存在于各种天文环境中，在这些环境中它们会受到强烈辐射。它们的光解离途径为了解宇宙中的物质循环提供了关键见解，但到目前为止，仅对少数PANHs的解离特性进行了研究。此外，大多数实验使用单光子技术，这些技术仅揭示初始解离步骤，因此不适合复制天文环境和时间尺度。在这项工作中，我们使用天体物理实验室的多环芳烃光动力学仪器（i-PoP）来模拟模型PANH阳离子三氮杂蒄（TAC˙，CHN）的星际光解离。将观察到的碎片与类似的多环芳烃（如等电子体蒄）进行比较，可以深入了解多环芳烃的解离机制。对于蒄，发现主要的光解离产物是CH、C和C。相比之下，TAC˙中的碎片化通常由多达三次HCN损失引发，常伴有H或H损失。在较低质量区域，碎片与类似的多环芳烃（如蒄）有相似之处，但对于TAC˙，还观察到氮原子以（二）氰基多炔的形式包含在离子碎片中。这些含氮物种可能是星际空间中PANHs正在发生光解离区域的重要示踪剂。
