C-$_6$ H，$^{13}$ C-$_6$ H和C-$_6$ D电子跃迁的光谱研究
A Spectroscopic Survey of Electronic Transitions of C$_6$H, $^{13}$C$_6$H, and C$_6$D
摘要：
利用超声膨胀烃等离子体的光腔衰荡光谱，在$18\,950-21\,100$ cm $^{-1}$域测量了C $_6$ H的电子光谱。总共，19（子）带的C $_6$ H，所有探测的振动流形的B $^2Π$电子激发态。分配的指导下，电子光谱可从矩阵隔离工作，同位素取代实验（也产生光谱$^{13}$ C $_6$ H和C $_6$ D），从头计算以及旋转拟合和振动轮廓模拟使用现有的基态参数从微波实验中获得的预测。除了$0_0^0$的起源带外，还确定了C-$_6$ H分子线性骨架上的三个非简并伸缩振动：与C-C键振动相关的$ν_6$模式和与C-$\equiv$ C三键相关的$ν_4$和$ν_3$模式.对于两个最低的$ν_{11}$和$ν_{10}$弯曲模式，进行Renner-Teller分析，识别$μ^2Σ$（$ν_{11}$）以及$μ^2Σ$（$ν_{10}$）和$κ^2Σ$（$ν_{10}$）组件。此外，还观察到两个较高的弯曲模式，它们被暂时指定为$μ^2Σ$（$ν_9$）和$μ^2Σ$（$ν_8$）水平。在第一非简并振动（$ν_6$）下面的激发区域中，观察到一些$^2Π-^{2}Π$跃迁，这些跃迁被分配为低位弯曲振动的偶组合模式。这同样适用于在$ν_6$水平之上发现的$^2Π-^{2}Π$转换。从这些光谱数据和振动分析的全面的B $^2Π$状态的C $_6$ H的能级图推导和提出。
英文摘要：
Electronic spectra of C$_6$H are measured in the $18\,950-21\,100$ cm$^{-1}$ domain using cavity ring-down spectroscopy of a supersonically expanding hydrocarbon plasma. In total, 19 (sub)bands of C$_6$H are presented, all probing the vibrational manifold of the B$^2Π$ electronically excited state. The assignments are guided by electronic spectra available from matrix isolation work, isotopic substitution experiments (yielding also spectra for $^{13}$C$_6$H and C$_6$D), predictions from ab initio calculations as well as rotational fitting and vibrational contour simulations using the available ground state parameters as obtained from microwave experiments. Besides the $0_0^0$ origin band, three non-degenerate stretching vibrations along the linear backbone of the C$_6$H molecule are assigned: the $ν_6$ mode associated with the C-C bond vibration and the $ν_4$ and $ν_3$ modes associated with C$\equiv$C triple bonds. For the two lowest $ν_{11}$ and $ν_{10}$ bending modes, a Renner-Teller analysis is performed identifying the $μ^2Σ$($ν_{11}$) and both $μ^2Σ$($ν_{10}$) and $κ^2Σ$($ν_{10}$) components. In addition, two higher lying bending modes are observed, which are tentatively assigned as $μ^2Σ$($ν_9$) and $μ^2Σ$($ν_8$) levels. In the excitation region below the first non-degenerate vibration ($ν_6$), some $^2Π-^{2}Π$ transitions are observed that are assigned as even combination modes of low-lying bending vibrations. The same holds for a $^2Π-^{2}Π$ transition found above the $ν_6$ level. From these spectroscopic data and the vibronic analysis a comprehensive energy level diagram for the B$^2Π$ state of C$_6$H is derived and presented.
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