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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Infrared Spectroscopy of Matrix Isolated Polycyclic Aromatic Hydrocarbons. 1. PAHs Containing Two to Four Rings
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Infrared Spectroscopy of Matrix Isolated Polycyclic Aromatic Hydrocarbons. 1. PAHs Containing Two to Four Rings

机译：基质分离的多环芳烃的红外光谱。 1.含有两到四个环的PAH

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Matrix isolation techniques have been used to measure the mid-infrared spectra of the polycyclic aromatic hydrocarbons (PAHs) naphthalene, anthracene, phenanthrene, 1, 2-benzanthracene, chrysene, pyrene, tetracene, and triphenylene. The band positions and relative strengths are compared to previous laboratory studies, where available, and with available theoretical calculations. Comparisons with theory indicate that density functional theory (DFT) does an excellent job of describing the majority of the infrared active fundamentals of the PAHs considered here. Band positions typically match to within 5 cm~(-1), with the worst mismatches usually no more than 15 cm~(-1). Matches in band strengths are not as precise but, with the exception of the CH stretching bands, are generally good to better than 35% for most strong and moderate bands and to factors of 2 to 3 for weaker bands. Theory predicts CH stretching band strengths that are about a factor of 2 times too strong. The laboratory spectra contain large numbers of bands due to overtone/combination modes that are not considered in the calculations, and while most of these bands are weak, some can be moderately strong. Finally, comparisons between the infrared spectra of matrix isolated PAHs and a common family of interstellar emission bands confirm that neutral PAHs do not provide a good fit to the astronomical data. Neutral PAHs produce features having appropriate frequencies but generally inappropriate strengths. Nevertheless, significant contributions from PAH neutrals may be required to explain the spectra of a few less energetic astronomical environments.
机译：基质分离技术已用于测量多环芳烃（PAHs）萘，蒽，菲，1、2-苯并蒽，ry 、,、并四苯和三亚苯基的中红外光谱。将带的位置和相对强度与以前的实验室研究（如果有的话）进行比较，并进行理论计算。与理论的比较表明，密度泛函理论（DFT）在描述此处考虑的PAH的大部分红外活性基础方面做得非常出色。频段位置通常匹配在5 cm〜（-1）以内，最差的不匹配通常不超过15 cm〜（-1）。频段强度的匹配并不那么精确，但是，除了CH拉伸频段以外，对于大多数强频段和中频段，通常好于35％，而对于弱频段则为2-3。理论预测CH拉伸带强度大约是强度的2倍。由于在计算中未考虑泛音/组合模式，因此实验室光谱包含大量频带，尽管这些频带中的大多数较弱，但有些频带可能中等强。最后，矩阵隔离的PAH的红外光谱与星际发射带的常见族之间的比较证实，中性PAH不能很好地适合天文数据。中性PAH产生具有适当频率但强度通常不合适的特征。然而，可能需要PAH中性物质做出重大贡献来解释一些能量较低的天文环境的光谱。

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