Experimental study of the formation and destruction of carbonates in circumstellar and interstellar environments and their impact on the oxygen depletion in the interstellar medium

星周和星际环境中碳酸盐的形成和破坏及其对星际介质耗氧影响的实验研究

• 批准号: 451244650
• 负责人: Dr. Cornelia Jäger
• 金额: --
• 依托单位: Laboratory Astrophysics and Cluster Physics Group
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/451244650?language=en
• 关键词: Experimental; study; formation; destruction; carbonates

Carbonates are found in various astrophysical environments including circumstellar envelopes around evolved stars, protoplanetary disks, solar and extrasolar planets, and comets. Their formation and destruction in astrophysical environments is a complex interplay between different refractory and nonrefractory solids, gaseous components, and irradiation with energetic photons. Carbonates can be formed from silicates and carbonaceous material. A considerable amount of carbon and in particular of oxygen can be sequestered in such inorganic and organic carbonates, which provides a possible solution to the oxygen depletion problem in the interstellar medium. In the course of the project, we are going to simulate the formation and destruction of carbonates in the laboratory at conditions prevailing in various astrophysical environments. Inorganic and organic carbonates will be produced from carbonaceous and silicate dust analogues produced in our laboratory. The carbonation of silicates will be realized by gas phase condensation in CO2/H2O-containing atmospheres, gas-surface reactions between CO, CO2, and H2O molecules and cosmic silicate analogues, reactions of cold silicates or silicate/carbon mixtures with molecular ice composed of CO, CO2, and H2O. In addition, the effect of simultaneous ultraviolet irradiation on the carbonate formation produced from silicates either in the gas phase or at the interface grains/ice will be investigated. The exposure of carbon grains to a bombardment of oxygen atoms and a flow of CO and CO2 molecules will be used to synthesize organic carbonates. Their formation is expected to occur in two reaction steps including the formation of epoxide functional groups and their reaction into cyclic carbonates. IR spectroscopy will be used to monitor the formation of inorganic and organic carbonates in situ. The formation rates will be determined as a function of temperature covering a range between 10 K and ~400 K. IR spectroscopy, electron microscopy, and organic analyses will be used to explain the chemical and structural modifications of the silicate and carbon grains. Besides the formation rate of carbonates, their photon-induced destruction by VUV irradiation plays an important role and has to be analyzed. The results of our studies will provide us significant information on the spectral properties of cosmic carbonates and their potential role in astrochemical and astrophysical processes such as the depletion of oxygen and the formation of complex organic molecules in the interstellar medium, as well as the formation of planets.

碳酸盐存在于各种天体物理环境中，包括进化恒星周围的星周包层、原行星盘、太阳和太阳系外行星以及彗星。它们在天体物理环境中的形成和破坏是不同难熔和非难熔固体、气体成分和高能光子辐照之间复杂的相互作用。碳酸盐可以由硅酸盐和碳质材料形成。大量的碳，特别是氧可以被隔离在这种无机和有机碳酸盐中，这为星际介质中的氧耗尽问题提供了一种可能的解决方案。在项目过程中，我们将在实验室中模拟各种天体物理环境下碳酸盐的形成和破坏。无机和有机碳酸盐将从我们实验室生产的碳质和硅酸盐粉尘类似物中产生。硅酸盐的碳酸化将通过在含CO2/H2O的气氛中的气相冷凝、CO、CO2和H2O分子与宇宙硅酸盐类似物之间的气体表面反应、冷硅酸盐或硅酸盐/碳混合物与由CO、CO2和H2O组成的分子冰的反应来实现。此外，同时紫外线照射对碳酸盐的形成产生的硅酸盐无论是在气相中或在界面晶粒/冰的影响将进行调查。碳颗粒暴露于氧原子的轰击和CO和CO2分子流将用于合成有机碳酸酯。它们的形成预计在两个反应步骤中发生，包括形成环氧官能团和它们反应成环状碳酸酯。红外光谱将用于监测无机和有机碳酸盐的形成在原位。形成速率将被确定为温度的函数，覆盖10 K和~400 K之间的范围。红外光谱，电子显微镜，和有机分析将被用来解释硅酸盐和碳颗粒的化学和结构的修改。除了碳酸盐的形成速率外，真空紫外辐照对碳酸盐的光致破坏也起着重要作用，必须加以分析。我们的研究结果将为我们提供有关宇宙碳酸盐的光谱特性及其在天体化学和天体物理过程中的潜在作用的重要信息，例如星际介质中氧气的耗尽和复杂有机分子的形成，以及行星的形成。