Vinylsulfur pentafluoride (VSPF), a molecule with a four-fold internal rotor, —SF₄, has been studied with high resolution Fourier transform microwave spectroscopy. We believe that this is the first report of resolved four-fold internal rotation. As such, we have presented the tools needed to understand and analyze such a problem. These include debugging the ERHAM computer program necessary to fit the spectra and the free rotor to high barrier correlation diagram necessary to understand the torsional states of the four-fold rotor. The A, E, and B torsional state rotational transitions are well resolved and assigned. Spectroscopic transitions of four isotopologues of VSPF, H₂C=CH—SF₅, the normal isotopologue, and the singly substituted ³⁴S and ¹³C isotopologues were measured and assigned. Contrary to expectation, the A torsional state could not be fit with only a semi-rigid Hamiltonian. The barrier to internal rotation, V₄, is found to be 227 cm⁻¹. Ab initio calculations at the MP2 aug-cc-pVQZ level of theory and basis set were performed and the results of this calculation are compared to our experimental results.

中文翻译：

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扭转分裂和内部旋转的四重障碍：五氟化乙烯硫的旋转光谱

五氟乙烯硫（VSPF）是具有四倍内转子-SF ₄的分子，已通过高分辨率傅立叶变换微波光谱法进行了研究。我们认为，这是解决四重内部轮换的第一份报告。因此，我们提供了理解和分析此类问题所需的工具。其中包括调试ERHAM计算机程序以适应光谱，将自由转子调试为了解四重转子扭转状态所需的高势垒相关图。的甲，ê，和乙扭转状态转动跃迁被良好分辨，并分配。VSPF，H ₂ C = CH-SF ₅的四个同位素的光谱跃迁，正常同位素，单取代的³⁴ S和¹³ C同位素进行了测量和分配。与预期相反，在一个扭曲的状态是不配，只有一个半刚性哈密顿。发现内部旋转的屏障V ₄为227 cm ^-1。在理论和基础集的MP2 aug-cc-pVQZ级别进行了从头算计算，并将该计算结果与我们的实验结果进行了比较。