氰基取代的多环芳烃分子的非谐红外发射：以氰基萘为例
Anharmonic Infrared Emission of Cyano-Substituted Polycyclic Aromatic Hydrocarbon Molecules: Cyanonaphthalenes as a Case Study
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中文总结 AI 辅助
研究氰基取代的多环芳烃分子红外发射，用B3LYP/N07D和VPT2计算非谐性质并模拟光谱，发现电荷态等对发射有影响，给出异构体特征及能量分数，为约束氰基PAH丰度提供工具，助力JWST观测分析
中文摘要 AI 辅助
最近对氰基取代的多环芳烃（cyano-PAHs）的探测突出了它们作为星际介质中氮杂环的关键示踪剂。然而，它们的红外（IR）识别需要考虑不同环境中动态冷却的非谐振动辐射模型。我们提供了在代表性天体物理条件下中性、阳离子和阴离子的1-和2-氰基萘（1-和2-CNN）的红外级联发射光谱，研究电荷态和取代位置如何在红外级联过程中调节非谐轮廓和能量重新分布。使用B3LYP/N07D和二阶振动微扰理论（VPT2），我们计算了非谐性质，并应用优化的微正则采样算法来计算态密度和模拟环境相关的级联光谱。结果表明，电荷态强烈调节CN腈带：与中性相比，阴离子强度增强了一个数量级，而阳离子强度略弱。1-和2-CNN呈现出不同的异构体特征：由于周边氢相互作用，1-CNN在3.3微米C-H伸缩振动中显示出复杂的“红翼”结构，而2-CNN产生更对称的轮廓。我们评估了通过CN伸缩振动相对于跨电荷态和环境的总级联发射率发射的分数能量。结合观测到的CN通量，这些分数提供了一个定量工具来约束氰基PAH的丰度。通过将实验室基准与动态星际发射联系起来，这项工作提供了准确的非谐指纹，以指导JWST观测分析
英文摘要
Recent detections of cyano-substituted polycyclic aromatic hydrocarbons (cyano-PAHs) highlight them as key tracers of nitrogen heterocycles in the interstellar medium (ISM). However, their infrared (IR) identification requires anharmonic vibrational radiative models that account for dynamic cooling across diverse environments. We provide IR cascade emission spectra for neutral, cationic, and anionic 1- and 2-cyanonaphthalene (1- and 2-CNN) under representative astrophysical conditions, investigating how charge states and substitution positions modulate anharmonic profiles and energy redistribution during IR cascades. Using B3LYP/N07D with Second-order Vibrational Perturbation Theory (VPT2), we computed anharmonic properties and applied an optimized microcanonical sampling algorithm to calculate vibrational density of states and model environment-dependent cascade spectra. Results show that charge states strongly tune the CN nitrile band: anion intensity is enhanced by an order of magnitude compared to neutrals, whereas cation intensity is slightly weaker. 1- and 2-CNN present distinct isomeric signatures: 1-CNN displays a complex "red-wing" structure in the 3.3-micron C-H stretch due to peri-hydrogen interactions, whereas 2-CNN yields a more symmetric profile. We evaluated the fractional energy emitted via the CN stretch relative to total cascade emissivity across charge states and environments. Combined with observed CN fluxes, these fractions provide a quantitative tool to constrain cyano-PAH abundances. By bridging laboratory benchmarks with dynamic interstellar emission, this work delivers accurate anharmonic fingerprints to guide JWST observational analysis.
