由於冷星雲的內部溫度僅有10 K，經過了上百萬年的吸積，幾乎所有的分子（除了氫氣以外）都會冷凝成冰晶並附著在宇宙塵埃的表面上。根據現有的宇宙觀測，這些宇宙冰晶會形成一個雙層的結構[1]。在先前的研究中，我們在實驗室模擬了宇宙冰晶，長出了下層為水（H2O）：甲烷（13CH4）：氨氣（15NH3）＝2:1:1，上層為一氧化碳（CO）：甲醇（CH3OH）＝3:1 的冰晶。透過同位素的標定，發現了X射線的照射可以引發分子在冰晶內的擴散現象。來自下層的產物（如：13CO、13CO2 和15N2等）穿過上層，並從冰晶的表面脫附。因為X射線會生成大量的二次電子，同時宇宙射線也會生成真空紫外光，在本次研究中我們分別使用了電子及真空紫外光進行照射，同樣發現了來自下層的產物從冰晶的表面脫附。這個結果證明了電子及真空紫外光也能引發擴散現象。透過建立模型，將能夠計算出CO 在冰晶中的擴散係數，並將與X射線的結果進行比較。;In the interior of a cold dense cloud, since the temperature is as low as 10 K, the molecules condense to dust grains. According to the observational data, these ices are expected to form a double-layered structure. In previous studies, we found that X-ray can induce the bulk diffusion in the realistic-like double-layered ices which include H2O + 13CH4 + 15NH3 (2:1:1) in the bottom layer and CO + CH3OH (3:1) in the top layer. The species produced in bottom layer, such as 13CO, 13CO2 and 15N2, desorbed from the ices. Since X-ray generate secondary electrons and cosmic ray can induced vacuum ultraviolet (VUV) field, we studied the realistic-like double-layered ice under electron and VUV irradiation and found the desorption of species from the bottom layer. These results proved that the species produced in bottom layer can diffuse through the top layer. Then we developed some models to calculate the diffusion coefficient of CO in the realistic double-layered ices and compared with the diffusion coefficient under X-ray irradiation.
