Evolution of porosity and structure of Amorphous Solid Water (ASW)

This experiment will measure the microstructure of Amorphous Solid Water (ASW), a porousmaterial that can be formed by vapour-depositing water onto a cold plate, an excellent analogue ofthe ice found in star- and planet-forming regions of our galaxy. The thermal and temporal evolutionof this metastable condensed-matter material has major implications in the physical and chemicalrole ices play in astrophysical environments. Our previous results on ISIS NIMROD has shown thatthe ASW has very small-scale porosity, and hints at larger scale structure of the material; and our recentresults on ISIS SANS2D showed a good overlap with these data and gave us information about aggregation and collapse of pores.This experiments aims to reproduce these results at various temperatures to elucidate how the deposition temperature modifies the pores thermal evolution.

本实验将对无定形固态水（Amorphous Solid Water，ASW）的微观结构进行表征。无定形固态水是一种可通过将水蒸气气相沉积至冷板表面制备得到的多孔材料，同时也是银河系恒星与行星形成区域中存在的冰的绝佳模拟物。这种亚稳态凝聚态材料的热演化与时间演化，对于理解冰在天体物理环境中所扮演的物理与化学角色具有重要意义。我们此前在ISIS NIMROD设备上得到的实验结果表明，ASW具有极细微尺度的孔隙结构，并暗示了该材料存在更大尺度的结构；近期在ISIS SANS2D设备上的实验结果则与前述数据高度吻合，同时为我们提供了关于孔隙聚集与坍缩的相关信息。本实验旨在通过在不同沉积温度下复现上述实验结果，阐明沉积温度如何调控孔隙的热演化过程。