The discovery of carbon-rich species, including polycyclic aromatic hydrocarbons (PAH) and fullerenes, in the space environment is among the most intriguing findings in molecular astrophysics and astrochemistry of the recent decades. The mechanism of their formation remains unclear and the one of the key issues is related to making “first ring”, i.e., formation of benzene from simple small molecules abundant in the outer space. Different routes involving C2, C3 and C4 hydrocarbons are considered in literature. Here we report the first direct evidence for a single-step radiation-induced formation of benzene from pre-existing isolated acetylene trimer occurring in frozen inert environment at very low temperature (6 K). The finding is based on the correlation between trimer decay and build-up of benzene as monitored by FTIR spectroscopy. This concerted pathway may be applicable to acetylene aggregates trapped in the bulky ices or in the grain pores and it emphasizes the importance of concept of molecular organization in the chemical history of the Universe.

在太空环境中发现富含碳的物质，包括多环芳烃（PAH）和富勒烯，是近几十年来分子天体物理学和天化学中最引人入胜的发现之一。它们的形成机理仍不清楚，关键问题之一与“第一环”的制造有关，即由外层空间中丰富的简单小分子形成苯。文献中考虑了涉及C 2，C 3和C 4烃的不同途径。在这里，我们报告的第一个直接证据是在非常低的温度（6 K）下，在冻结的惰性环境中，由预先存在的分离的乙炔三聚体通过单步辐射诱导的苯形成。这一发现是基于三聚体衰变与苯堆积（通过FTIR光谱法进行监测）之间的相关性。