C $_3$的弯曲--$l$型倍增和共振的实验研究
The Bending of C$_3$: Experimentally Probing the $l$-type Doubling and Resonance
摘要：
C $_3$是一种在不同天文环境中发现的纯碳链分子，通过观测其基态电子态的低弯曲模（$ν_2$）跃迁，被认为是一种很好的动力学温度探测器。目前的实验室工作的目的是调查这种弯曲模式与多量子的激发相结合的高分辨率的光学和红外光谱的C $_3$放电实验中产生的记录。在中国科学技术大学用单纵模光参量振荡器作为窄带光源，用激光诱导荧光光谱法记录了A $^1Π_u -$ X $^1Σ_g^+$的旋振子跃迁光谱。分配源自X（0 $v_2$ 0），$v_2 = 0-5$的36个频带。在SOLEIL同步加速器的AILES光束线上，用球泡光源，用傅里叶变换红外光谱法记录了转振$ν_3$带的中红外光谱。光谱揭示了涉及$ν_2$中多达5个激发量子的热带。从目前记录的所有光谱和文献数据相结合的分析，准确的旋转参数和绝对能级的C $_3$，特别是涉及弯曲模式的状态，确定。使用包含涉及X和A状态的所有可用数据（文献和本研究）的单个PGOPHER文件来拟合所有数据。从这项工作中获得的光谱信息，使新的星际搜索C $_3$，不仅在红外和光学区域的调查，但也值得注意的是在$ν_2$带区域（约63厘米$^{-1}$），振动卫星现在可以准确地预测。这使得C $_3$成为一个通用的诊断工具，可以研究从黑暗和密集到半透明的云的各种不同的天文环境。
英文摘要：
C$_3$, a pure carbon chain molecule that has been identified in different astronomical environments, is considered a good probe of kinetic temperatures through observation of transitions involving its low-lying bending mode ($ν_2$) in its ground electronic state. The present laboratory work aims to investigate this bending mode with multiple quanta of excitation by combining recordings of high resolution optical and infrared spectra of C$_3$ produced in discharge experiments. The optical spectra of rovibronic (A $^1Π_u -$ X $^1Σ_g^+$) transitions have been recorded by laser induced fluorescence spectroscopy using a single longitude mode optical parametric oscillator as narrow bandwidth laser source at the University of Science and Technology of China. 36 bands originating from X(0$v_2$0), $v_2 = 0-5$, are assigned. The mid-infrared spectrum of the rovibrational $ν_3$ band has been recorded by Fourier-transform infrared spectroscopy using a globar source on the AILES beamline of the SOLEIL synchrotron facility. The spectrum reveals hot bands involving up to 5 quanta of excitation in $ν_2$. From combining analyses of all the presently recorded spectra and literature data, accurate rotational parameters and absolute energy levels of C$_3$, in particular for states involving the bending mode, are determined. A single PGOPHER file containing all available data involving the X and A states (literature and present study) is used to fit all the data. The spectroscopic information derived from this work enables new interstellar searches for C$_3$, not only in the infrared and optical regions investigated here but also notably in the $ν_2$ band region (around 63 cm$^{-1}$) where vibrational satellites can now be accurately predicted. This makes C$_3$ a universal diagnostic tool to study very different astronomical environments, from dark and dense to translucent clouds.
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