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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >The C-H Stretch Intensities of Polycyclic Aromatic Hydrocarbon Cations. Origins and Astrophysical Implications
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The C-H Stretch Intensities of Polycyclic Aromatic Hydrocarbon Cations. Origins and Astrophysical Implications

机译：多环芳烃阳离子的C-H拉伸强度。起源与天文学意义

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摘要

Infrared vibrational transition intensities of polycyclic aromatic hydrocarbons are known to depend strongly on the charge state. The detailed understanding of this effect for the C-H stretching modes has been approached by applying the quantum theory of atoms in molecules. Several benchmark calculations were undertaken in order to disentangle charge and size effects, from benzene (C6H6) up to the ovalene (C32H14) molecule. Upon decomposition of the dipole moment derivative along a C-H stretch into charge, charge flux, and dipole flux terms, it is found that it is the competition between the sum of the first two terms and the latter which drives the intensity, due to their opposing signs. Additionally, while the dipole flux term changes very little with size and charge, the other terms are strongly sensitive to these. This effect leads to a very weak C-H stretch intensity for cation sizes close to pyrene (C16H10) and comparable intensities between neutral and cations for the much larger ones. The astrophysical implications are discussed.
机译：已知多环芳族烃的红外振动跃迁强度强烈依赖于电荷状态。通过应用分子中原子的量子理论，可以深入了解这种对C-H拉伸模式的影响。为了消除电荷和尺寸效应，从苯（C6H6）到椭圆烯（C32H14）分子，进行了几次基准计算。沿着CH的偶极矩导数分解为电荷，电荷通量和偶极通量项时，发现前两项之和与后者之间的竞争驱动了强度，这是由于它们的相反迹象。此外，尽管偶极子通量项随尺寸和电荷的变化很小，但其他项对它们非常敏感。对于接近pyr（C16H10）的阳离子，此效应导致C-H拉伸强度非常弱，对于较大的阳离子，中性和阳离子之间的强度相当。讨论了天文学的意义。

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