Bouwman Jordy, Sztáray Bálint, Oomens Jos, Hemberger Patrick, Bodi Andras
Institute for Molecules and Materials, FELIX Laboratory, Radboud University Nijmegen , Toernooiveld 7c, NL-6525 ED Nijmegen, The Netherlands.
J Phys Chem A. 2015 Feb 19;119(7):1127-36. doi: 10.1021/jp5121993. Epub 2015 Feb 9.
Two nitrogen-containing polycyclic aromatic hydrocarbon isomers of C9H7N composition, quinoline, and isoquinoline have been studied by imaging photoelectron photoion coincidence spectroscopy at the VUV beamline of the Swiss Light Source. High resolution threshold photoelectron spectra have been recorded and are interpreted applying a Franck-Condon model. Dissociative ionization mass spectra as a function of the parent ion internal energy are analyzed with the use of breakdown diagrams. HCN loss and H loss are the dominant dissociation paths for both C9H7N(•+) isomers at photon energies below 15.5 eV. Computed C9H7N(•+) potential energy surfaces suggest that the lowest energy path leading to HCN-loss yields the benzocyclobutadiene cation. A statistical model is used to fit the breakdown diagram and-to account for the kinetic shift-the time-of-flight mass spectra that reveal the dissociation rates. We have derived appearance energies of 11.9 ± 0.1 (HCN loss) and 12.0 ± 0.1 (H loss), as well as 11.6 ± 0.2 (HCN loss) and 12.1 ± 0.2 (H loss) eV, for the dissociative ionization of quinoline and isoquinoline, respectively. The results are compared to a recent study on the dissociative ionization of naphthalene. Implications for the formation and destruction of nitrogenated PAHs in the interstellar medium and in Titan's atmosphere are highlighted.
由瑞士光源的真空紫外光束线通过成像光电子光离子符合光谱法研究了两种化学式为C9H7N的含氮多环芳烃异构体喹啉和异喹啉。记录了高分辨率阈值光电子能谱，并应用弗兰克-康登模型进行了解释。利用分解图分析了作为母离子内能函数的离解电离质谱。在光子能量低于15.5 eV时，HCN损失和H损失是两种C9H7N(•+)异构体的主要离解途径。计算得到的C9H7N(•+)势能面表明，导致HCN损失的最低能量路径产生苯并环丁二烯阳离子。使用统计模型拟合分解图，并考虑动力学位移，即揭示离解速率的飞行时间质谱。我们分别得出喹啉和异喹啉离解电离的出现能为11.9±0.1（HCN损失）和12.0±0.1（H损失），以及11.6±0.2（HCN损失）和12.1±0.2（H损失）eV。将结果与最近关于萘离解电离的研究进行了比较。强调了对星际介质和土卫六大气中含氮多环芳烃形成和破坏的影响。
