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首页> 外文期刊>Physical chemistry chemical physics: PCCP >Accurate determination of low state rotational quantum numbers (J 4) from planar-jet and liquid nitrogen cell absorption spectra of methane near 1.4 micron
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Accurate determination of low state rotational quantum numbers (J 4) from planar-jet and liquid nitrogen cell absorption spectra of methane near 1.4 micron

机译：根据1.4微米附近甲烷的平面射流和液氮电池吸收光谱准确确定低态旋转量子数（J <4）

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摘要

An improved procedure for accurate determination of empirical lower state rotational quantum numbers from molecular absorption spectra is demonstrated for methane. We combine the high resolution absorption spectra in the 7070-7300 cm~(-1) frequency range obtained in liquid nitrogen cooled cryogenic cell (T = 81 K) and in supersonic planar jet expansion (T_R = 25 K), Empirical lower state energies of 59 transitions are determined from the ratio of the absolute absorption line strengths at 25 and 81 K. The procedure relies on the realistic description of rotational state populations in the supersonic jet expansion where non-equilibrium nuclear spin isomer distributions are generated due to the rapid cooling. The accuracy of the experimental determination of the lower state energies with J ≤ 3 is found to considerably improve the results of the same approach applied to spectra at 296 and 81 K. The 59 transitions with determined lower J values provide a good starting point for the theoretical interpretation of the highly congested icosad region of methane. In particular, the centres of nine vibrational bands are estimated from the transitions with J = 0 lower state rotational quantum number.
机译：演示了一种从分子吸收光谱准确确定经验较低态旋转量子数的改进程序。我们结合了在7070-7300 cm〜（-1）频率范围内在液氮冷却的低温电池（T = 81 K）和超音速平面射流膨胀（T_R = 25 K）中获得的高分辨率吸收光谱，经验低态能量从25和81 K处的绝对吸收谱线强度之比确定59个跃迁中的跃迁。该过程依赖于对超音速射流膨胀中旋转态总体的现实描述，在该超音速射流扩张中，由于快速生成非平衡核自旋异构体分布冷却。发现J≤3的较低态能量的实验确定的精度大大改善了在296和81 K处应用于光谱的相同方法的结果。确定的较低J值的59个跃迁为该方法提供了良好的起点。对甲烷高度拥塞的艾萨德地区的理论解释。特别地，从具有J = 0的低态旋转量子数的跃迁估计九个振动带的中心。

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