在TMC-1中发现了丙二烯基乙炔，H2CCCHCCH。C5H4异构体的研究
Discovery of allenyl acetylene, H2CCCHCCH, in TMC-1. A study of the isomers of C5H4
摘要：
通过对19条谱线的观测，我们在TMC-1中发现了丙二烯基乙炔（H2 CCCHCCH），谱线的信噪比为信噪比4-15。对于这个物种，我们推导出的旋转温度为7 +/- 1 K和柱密度为（1.2 +/- 0.2）e13 cm-2。该分子的另一个众所周知的异构体甲基二乙炔（CH 3C 4 H）也被观察到，我们推导出类似的旋转温度，Trot = 7.0 +/- 0.3 K，其两种状态（A和E）的柱密度为（6.5 +/- 0.3）e12 cm-2。因此，丙二烯基乙炔和甲基丁二炔具有相似的丰度。值得注意的是，它们的丰度接近乙烯基乙炔（CH 2CHCCH）。我们还搜索了C5 H4的另一种异构体HCCCH 2CCH（1.4-丙炔），但只能确定柱密度的3 σ上限为2.5e12 cm-2。这些结果已与TMC-1的最新化学模型进行了比较，表明这些烃在其化学中的重要作用。通过对TMC-1中观测到的跃迁频率和实验数据的拟合，改进了联烯基乙炔的转动参数。
英文摘要：
We present the discovery in TMC-1 of allenyl acetylene, H2CCCHCCH, through the observation of nineteen lines with a signal-to-noise ratio ~4-15. For this species, we derived a rotational temperature of 7 +/- 1 K and a column density of (1.2 +/- 0.2)e13 cm-2. The other well known isomer of this molecule, methyl diacetylene (CH3C4H), has also been observed and we derived a similar rotational temperature, Trot = 7.0 +/- 0.3 K, and a column density for its two states (A and E) of (6.5 +/- 0.3)e12 cm-2. Hence, allenyl acetylene and methyl diacetylene have a similar abundance. Remarkably, their abundances are close to that of vinyl acetylene (CH2CHCCH). We also searched for the other isomer of C5H4, HCCCH2CCH (1.4-pentadiyne), but only a 3sigma upper limit of 2.5e12 cm-2 to the column density can be established. These results have been compared to state-of-the-art chemical models for TMC-1, indicating the important role of these hydrocarbons in its chemistry. The rotational parameters of allenyl acetylene have been improved by fitting the existing laboratory data together with the frequencies of the transitions observed in TMC-1.
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