甲酰胺冰的光处理：通向太空中的前生物化学的途径
Photoprocessing of formamide ice: route towards prebiotic chemistry in space
摘要：
目标。甲酰胺（HCONH 2）是最简单的含有肽键的分子，首先在Orion-KL和SgrB 2的气相中检测到。近年来，人们在热科里诺斯等高温区域观察到了这种现象，在那里，热脱附是导致冷冻地幔升华为气相的原因。对观测结果的解释可得益于在实验室收集的信息，因为在实验室可以模拟热解吸过程，并在模拟的空间条件下研究甲酰胺，如紫外线照射。方法.在这里，两个实验室分析报告：我们研究了甲酰胺光稳定性在紫外线照射下，当它被吸附的空间相关的矿物在63 K和真空制度。我们还研究了程序升温脱附纯甲酰胺冰的存在下，二氧化钛粉尘之前和之后的紫外线照射。结果通过这些分析，紫外光降解的影响和甲酰胺和不同矿物之间的相互作用进行了比较。我们发现，硅酸盐，无论是水合物和脱水物，提供了更高水平的保护分子的紫外光降解比矿物氧化物。纯甲酰胺的脱附温度为220 K。当甲酰胺从TiO 2颗粒表面脱附时，脱附温度升高到250 K。结论.通过这里概述的实验，可以跟踪甲酰胺及其碎片的解吸，模拟恒星形成区和热科里诺的解吸过程，并限制参数，如甲酰胺及其碎片的热解吸温度和所涉及的结合能。我们的研究结果为观测数据提供了支持，并提高了我们对颗粒表面在丰富空间化学中的作用的理解。
英文摘要：
Aims. Formamide (HCONH2) is the simplest molecule containing the peptide bond first detected in the gas phase in Orion-KL and SgrB2. In recent years, it has been observed in high temperature regions such as hot corinos, where thermal desorption is responsible for the sublimation of frozen mantles into the gas phase. The interpretation of observations can benefit from information gathered in the laboratory, where it is possible to simulate the thermal desorption process and to study formamide under simulated space conditions such as UV irradiation. Methods. Here, two laboratory analyses are reported: we studied formamide photo-stability under UV irradiation when it is adsorbed by space relevant minerals at 63 K and in the vacuum regime. We also investigated temperature programmed desorption of pure formamide ice in the presence of TiO2 dust before and after UV irradiation. Results. Through these analyses, the effects of UV degradation and the interaction between formamide and different minerals are compared.We find that silicates, both hydrates and anhydrates, offer molecules a higher level of protection from UV degradation than mineral oxides. The desorption temperature found for pure formamide is 220 K. The desorption temperature increases to 250 K when the formamide desorbs from the surface of TiO2 grains. Conclusions. Through the experiments outlined here, it is possible to follow the desorption of formamide and its fragments, simulate the desorption process in star forming regions and hot corinos, and constrain parameters such as the thermal desorption temperature of formamide and its fragments and the binding energies involved. Our results offer support to observational data and improve our understanding of the role of the grain surface in enriching the chemistry in space.
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