Energetic photon irradiation of carbonaceous icy grains–laboratory studies on the interstellar ice-dust interface in star-forming regions

在密集的星际介质中，宇宙尘埃颗粒被一层分子冰层覆盖。这些由难熔成分和挥发成分组成的颗粒有望被高能光子连续照射。光子可以穿透尘埃颗粒上约10纳米的薄分子冰层。它们可以与耐火粉尘材料相互作用，在冰/粉尘材料和冰-粉尘界面处激活光子诱导反应。耶拿天体物理实验室和星团物理小组与台湾光处理光谱学实验室的拟议项目致力于研究星际介质和恒星形成区域中冰尘颗粒的光子诱导修饰。由于颗粒尺寸小，粉尘团聚体的孔隙率高，冰与粉尘界面的接触面积大。建立DFG-MOST联合研究项目，研究由真空紫外光子（E <10.9 eV）、极紫外光子（E=11-40 eV）和软x射线光子（E= 80-1200 eV）组成的高能光子触发的冰尘界面加工。本研究将解决三个不同的目标，即自由基与碳质粉尘表面可能的相互作用导致材料的侵蚀，冰-粉尘界面上有机和益生元分子的形成以及高能光子对耐火粉尘材料组成和结构的影响。我们将包括非晶和氢化非晶碳纳米颗粒与富勒烯类结构亚基和硅酸盐/碳混合物。系统的实验研究了典型星际参数（如温度和光子能量）对纯冰覆盖的尘埃类似物（包括H2O， NH3, CH4, H2S， N2和O2）的函数。这个高能颗粒/冰处理项目的成果将提高我们对星际颗粒演化的认识，并有助于更好地了解行星系统和行星的成分。它对天体化学、天体生物学和（外）行星科学也很重要。预计2021年发射的詹姆斯·韦伯太空望远镜将以极高的红外光谱分辨率和灵敏度揭示星际冰和尘埃的细节，这是该研究项目的创新和及时准备。

In the dense interstellar medium, cosmic dust grains are covered by a molecular ice layer. These grains consisting of a refractory and a volatile component are expected to be continuously irradiated by energetic photons. Thin molecular ice layers of about 10 nm on dust grains can be penetrated by photons. They can interact with the refractory dust material activating photon-induced reactions in the ice/dust material and at the ice-dust interface. The proposed project between the Laboratory Astrophysics and Cluster Physics Group in Jena and the Photoprocessing Spectroscopy Laboratory in Taiwan is dedicated to the investigation of photon-induced modifications of ice-dust grains in the interstellar medium and in star-forming regions. The interface between ice and dust is characterized by a large contact area due to the small sizes of particles and the high porosity of the dust agglomerates. The joint research project under the DFG-MOST program is established to study the ice-dust interface processing triggered by energetic photons comprising vacuum ultraviolet photons (E <10.9 eV), extreme ultraviolet photons (E=11-40 eV), and soft X-ray photons (E= 80-1200 eV). This research will address three different objectives namely the possible interactions of radicals with carbonaceous dust surfaces leading to the erosion of the material, the formation of organic and prebiotic molecules at the ice-dust interface and the effect of energetic photons on the composition and structure of the refractory dust materials. We will include amorphous and hydrogenated amorphous carbon nanoparticles with fullerene-like structural subunits and silicate/carbon mixtures. Systematic experimental studies as a function of typical interstellar parameters such as temperature and photon energy will be performed on dust analogs covered by pure ices including H2O, NH3, CH4, H2S, N2 and O2. The outcome of this project on energetic grain/ice processing will improve our knowledge on the interstellar grain evolution and will help to better understand the ingredients of planetary systems and planets. It will also be important for Astrochemistry, Astrobiology, and (Exo-)Planetary Science. The research project is an innovative and timely preparation of the upcoming James Webb Space Telescope expected to be launched in 2021, which will reveal the details of interstellar ice and dust in exceptionally high IR spectral resolution and sensitivity.