Formation of GEMS from interstellar silicate dust

在演化的M型恒星或超新星的星周壳层中，通过气相凝聚形成的硅酸盐可能是宝石(嵌入金属和硫化物的玻璃)粒子的前身。在第二个应用阶段，我们将继续研究离子诱导处理和适度热处理过程中从太阳系前硅酸盐颗粒中形成宝石的可能途径。不同组成和结构的硅酸盐将在我们的实验室制备。与辉石和橄榄石化学计量比类似的无定形或部分结晶硅酸盐粉尘、纯镁硅酸盐、含有金属铁包裹体的不均匀硅酸盐和含有有机碳的硅酸盐将受到不同能量范围(400.1000和10.100 keV)的H+、He+等丰富和活性离子(如Fe+和C+离子)的离子辐照。此外，还将研究适度热处理和离子诱导处理相结合的方法，以模拟宝石的形态和结构特性。宝石中硫化铁的来源仍然是一个有争议的问题。首先将进行有关硫化物在离子辐照下的稳定性的研究。由于溅射、缺陷形成、多孔结构的形成以及可能的结晶过程，硅酸盐或硫化铁中的结构、化学和形态变化将通过卢瑟福背散射光谱(RBS)、电子显微镜、能量色散X射线分析(EDX)和红外光谱进行监测。这一结果将有助于理解宝石的起源，宝石属于开启了太阳系行星形成过程的最原始材料。

Silicates formed via gas-phase condensation in circumstellar shells of evolved M-type stars or in supernovae are the possible precursors for the GEMS (glass with embedded metal and sulfide) particles. In the second application period, we will continue our studies on the possible formation pathways of GEMS from presolar silicate grains by ion-induced processing accompanied by moderate annealing processes. Differently composed and structured silicates will be prepared in our laboratory. Amorphous or partly crystalline silicate dust analogs with pyroxene and olivine stoichiometry, pure magnesium silicates, inhomogeneous silicates containing metallic iron inclusions, and silicates containing organic carbon will be exposed to ion irradiation with H+, He+, but also abundant and reactive ions such as Fe+ and C+ cations in different energy ranges (10.100 and 400.1000 keV). In addition, the combination of moderate annealing and ion-induced processing will be studied to simulate the morphological and structural properties of GEMS. The origin of iron sulfide in GEMS is still a matter of debate. First studies dedicated to the stability of sulfide under ion irradiation will be performed. Structural, chemical, and morphological changes in the silicates or in iron sulfide due to sputtering, defect formation, formation of porous structures, and possible crystallization processes will be monitored by Rutherford backscattering spectroscopy (RBS), electron microscopy, energy dispersive X-ray analyses (EDX) and IR spectroscopy. The results will help to understand the origin of GEMS which belong to the most primitive materials that began the planet forming processes in our solar system.