Ryazantsev Sergey V, Feldman Vladimir I
Department of Chemistry, Lomonosov Moscow State University, Moscow 119991, Russia.
Phys Chem Chem Phys. 2015 Nov 11;17(45):30648-58. doi: 10.1039/c5cp05446j.
The effect of X-ray irradiation on the isolated formic acid molecules (HCOOH) in solid noble gas matrices (Xe, Kr, Ar, and Ne) at very low temperatures (6 K) was first studied by FTIR spectroscopy. Carbon oxides (CO and CO2) and hydrocarboxyl radicals (HOCO) have been detected as the principal degradation products. The formation of HOCO radicals represents a primary dissociation channel for formic acid, which was not reported previously under UV photolysis in solids. This reaction can be explained by the involvement of the recombination-induced excited states, which are not populated in photolysis. The effects of the matrix and the absorbed dose on the product formation were studied in detail and possible mechanisms are discussed with particular attention to the difference between radiolysis and UV-photolysis of the matrix-isolated formic acid. The results obtained provide a new insight into the effects of high-energy impact on the simplest carboxylic acid with possible implications to the astrochemical problems, in particular, the prebiotic evolution in the interstellar medium.
通过傅里叶变换红外光谱（FTIR）首次研究了在极低温（6K）下，X射线辐照对固体稀有气体基质（Xe、Kr、Ar和Ne）中分离出的甲酸分子（HCOOH）的影响。已检测到碳氧化物（CO和CO2）和氢羧基自由基（HOCO）作为主要降解产物。HOCO自由基的形成代表了甲酸的一个主要解离通道，这在以前固体中的紫外光解过程中未曾报道过。该反应可以通过复合诱导激发态的参与来解释，而这些激发态在光解过程中并未出现。详细研究了基质和吸收剂量对产物形成的影响，并讨论了可能的机制，特别关注基质隔离甲酸的辐射分解和紫外光解之间的差异。所获得的结果为高能撞击对最简单羧酸的影响提供了新的见解，这可能对天体化学问题，特别是星际介质中的益生元进化产生影响。
