Non-detection of HC11N towards TMC-1: constraining the chemistry of large carbon-chain molecules
Non-detection of HC11N towards TMC-1: constraining the chemistry of large carbon-chain molecules
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未检测到 TMC-1 的 HC11N：限制大碳链分子的化学性质
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
A. Remijan
中科院分区：
文献类型：
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作者：
R. Loomis;C. Shingledecker;G. Langston;B. McGuire;Niklaus M. Dollhopf;A. Burkhardt;J. Corby;S. Booth;P. B. Carroll;B. Turner;A. Remijan
Bell等人报道了首次在冷黑云TMC-1中检测到氰聚烷HC_(11)N；后来没有向任何来源报告发现病毒。另外对氰聚烷和其他碳链分子向TMC-1方向的观测显示，分子大小和柱密度之间呈对数线性趋势，为了进一步探索驱动这一趋势的潜在化学过程，我们分析了绿岸望远镜对HC_9N和HC_(11)N向TMC-1方向的观测结果。虽然我们发现HC_9N的柱密度与之前的值一致，但没有检测到HC_(11)N，我们得出的柱密度上限明显低于Bell等人的报告。使用最先进的化学模型，我们研究了柱密度趋势非线性的可能解释。尽管更新了化学模型以更好地解释离子-偶极子相互作用，但我们无法解释为什么没有检测到HC_(11)N，我们将其解释为以前未知的碳链化学的证据。我们认为环化反应可能是导致HC11N丰度减少的原因，这些环化反应的产物应该作为候选星际分子进行研究。
Bell et al. reported the first detection of the cyanopolyyne HC_(11)N towards the cold dark cloud TMC-1; no subsequent detections have been reported towards any source. Additional observations of cyanopolyynes and other carbon-chain molecules towards TMC-1 have shown a log-linear trend between molecule size and column density, and in an effort to further explore the underlying chemical processes driving this trend, we have analysed Green Bank Telescope observations of HC_9N and HC_(11)N towards TMC-1. Although we find an HC_9N column density consistent with previous values, HC_(11)N is not detected and we derive an upper limit column density significantly below that reported in Bell et al. Using a state-of-the-art chemical model, we have investigated possible explanations of non-linearity in the column density trend. Despite updating the chemical model to better account for ion–dipole interactions, we are not able to explain the non-detection of HC_(11)N, and we interpret this as evidence of previously unknown carbon-chain chemistry. We propose that cyclization reactions may be responsible for the depleted HC11N abundance, and that products of these cyclization reactions should be investigated as candidate interstellar molecules.