标题： 辐射剂量影响空间中有机难熔材料的组成：来自实验室类似物的结果 显示英文标题

标题： Irradiation dose affects the composition of organic refractory materials in space: Results from laboratory analogues

摘要： 背景。 近红外和中红外观测揭示了太阳系中存在有机难熔材料，在彗核以及半人马座、柯伊伯带和海王星外天体的表面都有发现。 在这些天体物理环境中，由于冻结的挥发性化合物与宇宙射线、恒星/太阳粒子的相互作用，并得益于热处理，有机材料可以形成。 这类材料的实验室模拟分析提供了关于它们性质的信息，这与观测结果互补。 目标。 我们提出了新的实验，以帮助理解空间中有机难熔材料的化学成分。 方法。 我们用40 keV的H$^+$离子轰击水、甲醇和氨的混合冰，并将产物加热到300 K。 这些实验允许生成有机残留物，我们通过红外光谱和非常高分辨率质谱仪对其进行分析，研究它们的化学成分及其高分子多样性，包括六次甲基四胺及其衍生物的存在。 结果。 我们发现累积的辐照剂量在决定残留物组成方面起着作用。 结论。 基于实验室剂量，我们估计天体物理时间尺度足够短，可以在太阳系外部天体的表面诱导有机难熔材料的有效形成。 显示英文摘要

摘要： Context. Near- and mid-infrared observations have revealed the presence of organic refractory materials in the solar system, in cometary nuclei and on the surface of centaurs, Kuiper-belt and trans-neptunian objects. In these astrophysical environments, organic materials can be formed because of the interaction of frozen volatile compounds with cosmic rays, stellar/solar particles, and favoured by thermal processing. The analysis of laboratory analogues of such materials gives information on their properties, complementary to observations. Aims. We present new experiments to contribute in the understanding of the chemical composition of organic refractory materials in space. Methods. We bombard frozen water, methanol and ammonia mixtures with 40 keV H$^+$ and we warm the by-products up to 300~K. The experiments allow the production of organic residues that we analyse by means of infrared spectroscopy and by Very High Resolution Mass Spectrometry to study their chemical composition and their high molecular diversity, including the presence of hexamethylenetetramine and its derivatives. Results. We find that the accumulated irradiation dose plays a role in determining the residue's composition. Conslusions. Based on the laboratory doses, we estimate the astrophysical timescales to be short enough to induce an efficient formation of organic refractory materials at the surface of icy bodies in the outer solar system.