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首页> 外文期刊>The Astrophysical journal >LABORATORY DETECTION OF FIVE NEW LINEAR SILICON CARBIDES: SiC_3, SiC_5, SiC_6, SiC_7, AND SiC_8
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LABORATORY DETECTION OF FIVE NEW LINEAR SILICON CARBIDES: SiC_3, SiC_5, SiC_6, SiC_7, AND SiC_8

机译：五种新型线性硅碳化物的实验室检测：SiC_3，SiC_5，SiC_6，SiC_7和SiC_8

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摘要

The rotational spectra of five highly polar linear silicon-carbon chains SiC_n, n = 3 and 5-8, were detected by Fourier transform microwave spectroscopy in a supersonic molecular beam among the products of a gas discharge through silane and diacetylene; SiC_3 was detected as well by conventional millimeter-wave absorption spectroscopy in a large glow discharge through silane and acetylene. The electronic ground state was found to be X~1Σ~+ for those with even n and X~3Σ~- for those with odd n, in agreement with recent ab initio calculations. The rotational and centrifugal distortion constants of all five molecules were determined to high accuracy, as were the spin-spin and spin-rotation coupling constants for triplet SiC_3, SiC_5, and SiC_7. A fairly steep increase in the magnitude of the spin-spin constant with chain length, similar to that found previously for the C_n and C_nO chains, was observed for the present silicon carbides. Of the five new silicon carbides, SiC_3 is of particular astronomical interest because radio emission lines of the isomeric ground state, a compact rhomboidal ring, have recently been detected in IRC+10216 and because this chain is calculated to possess a large dipole moment of 4.8 D and to lie only 5 kcal mol~(-1) above ground. From the laboratory data, the most intense transitions of SiC_3 can now be calculated to better than 1 km s~(-1) in equivalent radial velocity at frequencies up to 300 GHz.
机译：通过傅立叶变换微波光谱法在通过硅烷和联乙炔进行气体放电的产物中的超音速分子束中检测了五个高极性线性硅碳链SiC_n（n = 3和5-8）的旋转光谱。 SiC_3也通过常规毫米波吸收光谱法在通过硅烷和乙炔的大辉光放电中检测到。与最近的从头算的结果一致，发现偶数为n的电子基态为X〜1Σ〜+，奇数为n的电子基态为X〜3Σ〜-。以高精度确定所有五个分子的旋转和离心畸变常数，以及三重态SiC_3，SiC_5和SiC_7的自旋-自旋和自旋-旋转耦合常数。对于本发明的碳化硅，观察到自旋-自旋常数随链长的变化相当陡峭，类似于先前对于C_n和C_nO链所发现的。在这五种新的碳化硅中，SiC_3具有特殊的天文学意义，因为最近在IRC + 10216中检测到了同质基态的无线电发射线，紧凑的菱形环，并且计算出该链具有4.8的大偶极矩。 D和位于地上仅5 kcal mol〜（-1）。根据实验室数据，现在可以计算出在高达300 GHz的频率下，等效径向速度下SiC_3的最强跃迁要好于1 km s〜（-1）。

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