Toward the limits of complexity of interstellar chemistry: Rotational spectroscopy and astronomical search for n- and i-butanal
M. Sanz-Novo, A. Belloche, V. M. Rivilla, R. T. Garrod, J. L. Alonso, P. Redondo, C. Barrientos, L. Kolesniková, J. C. Valle, L. Rodríguez-Almeida, I. Jiménez-S… 展开作者
M. Sanz-Novo, A. Belloche, V. M. Rivilla, R. T. Garrod, J. L. Alonso, P. Redondo, C. Barrientos, L. Kolesniková, J. C. Valle, L. Rodríguez-Almeida, I. Jiménez-Serra, J. Martín-Pintado, H. S. P. Muller, K. Menten
In recent times, large organic molecules of exceptional complexity have been found in diverse regions of the interstellar medium. In this context, we aim to provide accurate frequencies of the ground vibrational state of two key aliphatic aldehydes, n-butanal and its branched-chain isomer, i-butanal, to enable their eventual detection in the interstellar medium. We employ a frequency modulation millimeter-wave absorption spectrometer to measure the rotational features of n- and i-butanal. We use the spectral line survey ReMoCA performed with the Atacama Large Millimeter/submillimeter Array to search for n- and i-butanal toward the star-forming region Sgr B2(N). We also search for both aldehydes toward the molecular cloud G+0.693-0.027 with IRAM 30 m and Yebes 40 m observations. Several thousand rotational transitions belonging to the lowest-energy conformers have been assigned in the laboratory spectra up to 325 GHz. A precise set of the relevant rotational spectroscopic constants has been determined for each structure. We report non-detections of n- and i-butanal toward both sources, Sgr B2(N1S) and G+0.693-0.027. We find that n- and i-butanal are at least 2-6 and 6-18 times less abundant than acetaldehyde toward Sgr B2(N1S), respectively, and that n-butanal is at least 63 times less abundant than acetaldehyde toward G+0.693-0.027. Comparison with astrochemical models indicates good agreement between observed and simulated abundances (where available). Grain-surface chemistry appears sufficient to reproduce aldehyde ratios in G+0.693-0.027; gas-phase production may play a more active role in Sgr B2(N1S). Our astronomical results indicate that the family of interstellar aldehydes in the Galactic center region is characterized by a drop of one order of magnitude in abundance at each incrementation in the level of molecular complexity.
Interstellar Detection of the Highly Polar Five-Membered Ring Cyanocyclopentadiene
就像六元环一样，五元环在有机化学中无处不在，经常作为更大分子的构建单元，包括许多生物化学重要性。通过实验室旋转光谱学和对无星云核TMC-1的无线电波段的灵敏谱线测量相结合，我们报告了1-氰基-1，3-环戊二烯，$c$ -C $_5$ H $_5$ CN}的天文探测，它是环戊二烯的一种高极性氰基衍生物，$c$ -C $_5$ H $_6$。导出的$c$ -C $_5$ H $_5$ CN}的丰度远大于从天体化学模型中预测的，这些模型很好地再现了许多碳链的丰度。这一发现意味着可能需要考虑一种重要的生产机制或大量的芳香族物质。其密切相关的异构体2-氰基-1，3-环戊二烯的明显缺乏可能是由于其较低的稳定性，或者表明形成1-氰基异构体的选择性更高的途径，可能是从无环前体开始的途径。没有N-杂环，如吡咯和吡啶的天文发现进行了讨论。
Rotational spectroscopy and astronomical search of propane-1-thiol (CH3CH2CH2SH) and propane-2-thiol ((CH3)2CHSH)
University of Bologna（博洛尼亚大学）；Nanjing Institute of Atomic Scale Manufacturing（南京原子尺度制造研究所）；Centro de Astrobiología (CAB), CSIC-INTA（天体生物学中心（CAB），西班牙国家研究委员会-国家航空航天技术研究所）
