Experimental radiative cooling rates of a polycyclic aromatic hydrocarbon cation.
Experimental radiative cooling rates of a polycyclic aromatic hydrocarbon cation.
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多环芳烃阳离子的实验辐射冷却速率。
DOI：
10.1039/d3fd00005b
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发表时间：
2023
影响因子：
3.4
通讯作者：
Navarro Navarrete JE
中科院分区：
文献类型：
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作者：
Navarro Navarrete JE
利用射电望远镜观测，在金牛座分子云（TMC-1）中发现了几种小分子多环芳烃（PAHs）。再现这些分子的观测丰度一直是天体化学模型的挑战。通过循环荧光（RF）快速辐射冷却多环芳烃，从热填充的电子激发态发射光子，已被证明可以有效地稳定电离后的小型多环芳烃，增强其在天文环境中的弹性，并有助于合理化其观察到的高丰度。在这里，我们使用一种新的方法来实验确定的1-氰基萘（C10 H7 CN，1-CNN），其中的中性物种已被确定在TMC-1的阳离子的辐射冷却速率。分析了低温静电离子束储存环中隔离的1-CNN阳离子的激光诱导解离速率和动能释放分布，以跟踪初始热离子系综在冷却时的振动能量分布的时间演化。测得的冷却速率是在良好的协议与先前计算的RF速率系数。需要改进的测量和RF机制的模型来解释天文观测和改进星际多环芳烃稳定性的预测。
Several small Polycyclic Aromatic Hydrocarbons (PAHs) have been identified recently in the Taurus Molecular Cloud (TMC-1) using radio telescope observations. Reproducing the observed abundances of these molecules has been a challenge for astrochemical models. Rapid radiative cooling of PAHs by Recurrent Fluorescence (RF), the emission of optical photons from thermally populated electronically excited states, has been shown to efficiently stabilize small PAHs following ionization, augmenting their resilience in astronomical environments and helping to rationalize their observed high abundances. Here, we use a novel method to experimentally determine the radiative cooling rate of the cation of 1-cyanonaphthalene (C10H7CN, 1-CNN), the neutral species of which has been identified in TMC-1. Laser-induced dissociation rates and kinetic energy release distributions of 1-CNN cations isolated in a cryogenic electrostatic ion-beam storage ring are analysed to track the time evolution of the vibrational energy distribution of the initially hot ion ensemble as it cools. The measured cooling rate is in good agreement with the previously calculated RF rate coefficient. Improved measurements and models of the RF mechanism are needed to interpret astronomical observations and refine predictions of the stabilities of interstellar PAHs.