Abstract Very accurate transition frequencies of HC5N were determined between 5.3 and 21.4 GHz with a Fourier transform microwave spectrometer. The molecules were generated by passing a mixture of HC3N and C2H2 highly diluted in neon through a discharge valve followed by supersonic expansion into the Fabry-Perot cavity of the spectrometer. The accuracies of the data permitted us to improve the experimental 14 N nuclear quadrupole coupling parameter considerably and the first experimental determination of the 14 N nuclear spin-rotation parameter. The transition frequencies are also well suited to determine in astronomical observations the local speed of rest velocities in molecular clouds with high fidelity. The same setup was used to study HC7N, albeit with modest improvement of the experimental 14 N nuclear quadrupole coupling parameter. Quantum chemical calculations were carried out to determine 14 N nuclear quadrupole and spin-rotation coupling parameters of HC5N, HC7N, and related molecules. These calculations included evaluation of vibrational and relativistic corrections to the non-relativistic equilibrium quadrupole coupling parameters; their considerations improved the agreement between calculated and experimental values substantially.

中文翻译：

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氰基丁二炔HC5N精确静止频率和超精细结构参数的测定

摘要 HC5N 在 5.3 和 21.4 GHz 之间非常准确的跃迁频率是用傅立叶变换微波光谱仪确定的。这些分子是通过使在氖中高度稀释的 HC3N 和 C2H2 的混合物通过排放阀然后超音速膨胀进入光谱仪的法布里-珀罗腔而产生的。数据的准确性使我们能够显着提高实验 14 N 核四极耦合参数和 14 N 核自旋旋转参数的首次实验确定。跃迁频率也非常适合在天文观测中以高保真度确定分子云中静止速度的局部速度。使用相同的设置来研究 HC7N，尽管实验 14 N 核四极耦合参数略有改进。进行了量子化学计算以确定 14 N 核四极杆和 HC5N、HC7N 和相关分子的自旋-旋转耦合参数。这些计算包括对非相对论平衡四极耦合参数的振动和相对论修正的评估；他们的考虑大大提高了计算值和实验值之间的一致性。