论文标题
星际NC4NH+的发现：dicyanopolynes确实很丰富
Discovery of interstellar NC4NH+: dicyanopolyynes are indeed abundant in space
论文作者
论文摘要
先前检测与非极性分子氰基（NCCN），其质子化形式（NCCNH+）和一个亚稳态异构体（CNCN）有关的两个物种，在冷致密的云中支持了Dycyanopolynes在太空中丰富的假设。在这里，我们报告了NC4NH+空间中的第一个识别，即NC4N的质子化形式，NC4N是NCCN之后的Dicyanopolynes系列的第二个成员。该检测是基于对Yebes 40M线Quijote的Yebes 40m线调查中的六个和谐相关线的观察。可以将六条线拟合到旋转常数B = 1293.90840 +/- 0.00060 MHz，并且离心失真常数d = 28.59 +/- 1.21 Hz。我们基于高级估计计算，自信地将这一系列线分配给NC4NH+，该计算支持Marcelino等人的先前对HC5NH+的识别。 （2020）观察到一系列旋转常数2 MHz的线比此处得出的线。 TMC-1中NC4NH+的色谱柱密度为（1.1 +1.4 -0.6）E10 cm-2，这意味着NC4NH+比NCCNH+少了八倍。在后一种来源中，证实了先前报道的L483和TMC-1中的CNCN物种。我们估计NCCN和NC4N存在于TMC-1中，大量比HC3N和HC5N低几次。这意味着dicyanopolyynes nc-（cc）n-CN的存在低于相应的单核hcc-（cc）N-CN。自由基CN和C3N与HNC的反应是在冷致密云中最有可能的NCCN和NC4N的形成途径。
The previous detection of two species related to the non polar molecule cyanogen (NCCN), its protonated form (NCCNH+) and one metastable isomer (CNCN), in cold dense clouds supported the hypothesis that dicyanopolyynes are abundant in space. Here we report the first identification in space of NC4NH+, which is the protonated form of NC4N, the second member of the series of dicyanopolyynes after NCCN. The detection was based on the observation of six harmonically related lines within the Yebes 40m line survey of TMC-1 QUIJOTE. The six lines can be fitted to a rotational constant B = 1293.90840 +/- 0.00060 MHz and a centrifugal distortion constant D = 28.59 +/- 1.21 Hz. We confidently assign this series of lines to NC4NH+ based on high-level ab initio calculations, which supports the previous identification of HC5NH+ by Marcelino et al. (2020) from the observation of a series of lines with a rotational constant 2 MHz lower than that derived here. The column density of NC4NH+ in TMC-1 is (1.1 +1.4 -0.6)e10 cm-2, which implies that NC4NH+ is eight times less abundant than NCCNH+. The species CNCN, previously reported toward L483 and tentatively in TMC-1, is confirmed in this latter source. We estimate that NCCN and NC4N are present in TMC-1 with abundances a few times to one order of magnitude lower than HC3N and HC5N, respectively. This means that dicyanopolyynes NC-(CC)n-CN are present at a lower level than the corresponding monocyanopolyynes HCC-(CC)n-CN. The reactions of the radicals CN and C3N with HNC arise as the most likely formation pathways to NCCN and NC4N in cold dense clouds.
