Project P8: Temperature-dependent photostability and optical properties of realistic cometary ice composites

在升华距离之外，碎片盘中冰粒的主要侵蚀过程应该是紫外线光溅射，因为紫外线光子能够破坏水分子中的键，碎片可以从颗粒表面解吸。软x射线也能被吸收并引起电离和化学键断裂。在该项目中，我们将研究由水冰、天体物理相关分子和难熔颗粒混合组成的非均质颗粒在预测的碎片盘宿主恒星紫外线和x射线照射水平下的侵蚀和电阻率。水，分子和灰尘颗粒将同时沉积在冷基板上，可以保持在6到150 K之间。冰类似物将暴露在紫外线和x射线照射下。利用能量为10 eV的氢放电灯，研究了冰在紫外波段的光溅射。可以为同步加速器设施的各种x射线线提供3x108光子/s/cm2的天体物理相关x射线通量。利用原位紫外/可见光谱和红外光谱，结合蒸发物质的质谱分析，研究了污水冰的光致处理。在P1、P2和P4项目中，冰粒在紫外线和x射线照射下的电阻率以及光谱性质和形态的变化将用于开发更真实的圆盘模型。

Outside the sublimation distance, the dominant erosive process for ice grains in debris disks is supposed to be UV photosputtering since UV photons are able to break bonds in water molecules and fragments can be desorbed from the grain surfaces. Soft X-rays can also be absorbed and cause ionization and the breaking of bonds. In the project, we will study the erosion and resistivity of heterogeneous grains consisting of blends of water ice, astrophysically relevant molecules, and refractory grains to UV and X-ray irradiation at levels predicted for the debris disk host stars. H2O, molecules, and dust particles will be simultaneously deposited on cold substrates that can be kept at temperatures between 6 and 150 K. The ice analogs will be exposed to UV and Xray irradiation. A hydrogen discharge lamp providing photons with an energy of 10 eV will be used to study the photosputtering of ices in the UV range. Astrophysically relevant X-ray fluxes of 3x108 photons/s/cm2 can be provided for a variety of X-ray lines at synchrotron facilities. In-situ UV/VIS and IR spectroscopy of the ice layers in combination with mass spectrometry of evaporated species will be used to study the photo-induced processing of the dirty water ice. The resistivity of icy grains to UV and X-ray irradiation and changes in the spectral properties and morphology will be used to develop more realistic disk models in projects P1, P2 and P4.