High-resolution spectroscopy near the continuum limit: the microwave spectrum of trans -3-bromo-1,1,1,2,2-pentafluoropropane
High-resolution spectroscopy near the continuum limit: the microwave spectrum of trans -3-bromo-1,1,1,2,2-pentafluoropropane
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接近连续谱极限的高分辨率光谱：反式-3-溴-1,1,1,2,2-五氟丙烷的微波光谱
DOI：
10.1080/00268976.2018.1547845
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发表时间：
2018
影响因子：
1.7
通讯作者：
Grubbs II, G. S.
中科院分区：
文献类型：
--
作者：
Marshall, Frank E.;Moon, Nicole;Persinger, Thomas D.;Gillcrist, David J.;Shreve, Nelson E.;Bailey, William C.;Grubbs II, G. S.
用CP-FTMW光谱观察了3-溴-1，1，1，2，2-五氟丙烷的微波光谱。已经进行了势能扫描，并确认存在两种构象--Transandguche，对它们进行了进一步的结构优化和电场梯度计算，以便为分配目的获得高精度的核四极耦合常数。多个构象和大的核四极耦合常数的组合产生了非常密集的光谱，估计为1 跃迁/兆赫，接近连续谱极限。这种光谱密度使得有必要有非常复杂的计算方法，以获得非常接近实验观测的几何和电子结构。对光谱的分析允许指定变形体，但事实证明这是令人望而却步的，尽管它被认为存在于当前的光谱中。观察到并报道了两种同位素--79Br和81Br的转动光谱参数的完整分析。还报道了利用克拉奇曼坐标和二阶矩参数对实验观察到的构象进行几何分析。对光谱的进一步分析揭示了偶极禁止、核四极允许跃迁的发生，其中一个禁止跃迁具有第一已知的X型禁止跃迁连接路径。
The microwave spectrum of 3-bromo-1,1,1,2,2-pentafluoropropane has been observed using CP-FTMW spectroscopy. Potential energy scans have been performed and confirm the existence of two conformers –transandgauche– for which further structural optimisations and electric field gradient calculations have been performed in order to get highly accurate nuclear quadrupole coupling constants for assignment purposes. The combination of multiple conformers and large nuclear quadrupole coupling constants produce a very dense spectrum at an estimated 1 transition/MHz, near the continuum limit. This spectral density makes it necessary to have very sophisticated computational approaches in order to get geometric and electronic structures that are very close to experimental observation. Analysis of the spectrum allowed for the assignment of thetransconformer, but thegaucheproved to be prohibitive, although it is believed to be present in the current spectrum. Full analysis of the rotational spectroscopic parameters of two isotopologues – the79Br and81Br – have been observed and are reported. Geometric analysis of the experimentally observed conformer is also reported using Kraitchman coordinate and second moments arguments. Further analysis of the spectrum reveals the occurrence of dipole-forbidden, nuclear quadrupole allowed transitions with one forbidden transition possessing the first knownx-type forbidden transition linkage pathway.