Palotás Julianna, Martens Jonathan, Berden Giel, Oomens Jos
Institute for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525ED Nijmegen, The Netherlands.
van 't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098XH Amsterdam, The Netherlands.
J Phys Chem A. 2022 May 19;126(19):2928-2935. doi: 10.1021/acs.jpca.2c01329. Epub 2022 May 9.
We present the first experimental vibrational spectra of gaseous oxidized derivatives of C in protonated and radical cation forms, obtained through infrared multiple-photon dissociation spectroscopy using the FELIX free-electron laser. Neutral CO has two nearly iso-energetic isomers: the epoxide isomer in which the O atom bridges a CC bond that connects two six-membered rings and the annulene isomer in which the O atom inserts into a CC bond connecting a five- and a six-membered ring. To determine the isomer formed for CO in our experiment─a question that cannot be confidently answered on the basis of the DFT-computed stabilities alone─we compare our experimental IR spectra to vibrational spectra predicted by DFT calculations. We conclude that the annulene-like isomer is formed in our experiment. For COH, a strong OH stretch vibration observed in the 3 μm range of the spectrum immediately reveals its structure as C with a hydroxyl group attached, which is further confirmed by the spectrum in the 400-1600 cm range. We compare the experimental spectra of CO and COH to the astronomical IR emission spectrum of a fullerene-rich planetary nebula and discuss their astrophysical relevance.
我们展示了通过使用费利克斯（FELIX）自由电子激光的红外多光子解离光谱法获得的气态C氧化衍生物的质子化和自由基阳离子形式的首个实验振动光谱。中性的CO有两种能量几乎相同的异构体：环氧异构体，其中O原子桥接连接两个六元环的CC键；以及轮烯异构体，其中O原子插入连接一个五元环和一个六元环的CC键中。为了确定在我们的实验中形成的CO异构体——这是一个仅根据密度泛函理论（DFT）计算的稳定性无法可靠回答的问题——我们将实验红外光谱与DFT计算预测的振动光谱进行比较。我们得出结论，在我们的实验中形成了类似轮烯的异构体。对于COH，在光谱的3μm范围内观察到的强烈OH伸缩振动立即揭示了其结构为带有连接羟基的C，这在400 - 1600cm范围内的光谱中得到了进一步证实。我们将CO和COH的实验光谱与富含富勒烯的行星状星云的天文红外发射光谱进行比较，并讨论它们的天体物理相关性。
