Temperature Dependence of Effective Sites in Water Ice and Carbonaceous Dust Interactions

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题名:	Temperature Dependence of Effective Sites in Water Ice and Carbonaceous Dust Interactions
作者:	徐衍裕;Hsu, Yen-Yu
贡献者:	物理學系
关键词:	天文物理;天文化學;星際冰晶;水冰晶;碳基塵埃;真空紫外光誘發脫附;Astrophysics;Astrochemistry;Interstellar ice;Water ice;Carbonaceous dust;VUV-induced desorption
日期:	2024-08-15
上传时间:	2024-10-09 15:48:54 (UTC+8)
出版者:	國立中央大學
摘要:	近年來碳基塵埃引起了實驗室天文物理與天文化學領域中科學家的興趣，因為它有可能可以提供碳並與其他冰晶分子反映，進而形成一些複雜有機分子或是它們的前體。多項研究已經證實，在真空紫外線的照射後，固態水分子與碳基塵埃之間的相互作用會產生新的一氧化碳和二氧化碳的生成路徑 (Mennella et al. 2006; Shi et al. 2015)。然而這些研究中都沒有對冰晶覆蓋在塵埃上的情況提供深入的見解。這就引發了一個問題：當冰晶分子覆蓋在塵埃上時是否所有的冰晶分子皆與塵埃有所接觸，還是只有部分的冰晶分子?這個問題非常關鍵，因為碳基塵埃提供的反應位點的數量會大大影響這些含碳產物的產量 (Potapov et al. 2023)。因此，本研究旨在了解溫度如何影響固態水分子在碳基塵埃中的擴散以及碳基塵埃能提供的反應位點總數。在本研究中，我們將水分子在不同的溫度(13 K到150 K)下沉積到碳基塵埃上，並分析在經過真空紫外光照射後所生成的含碳產物的產量。實驗結果顯示，產量在100 K以下保持恆定，約為0.006分子/光子，但在100 K以上開始顯著增加，並在150 K時達到約0.01分子/光子的生成速率。這表明了水分子在碳基塵埃中的擴散確實可以增加反應位點的數量，從而影響含碳產物的產量。此外，我們在碳基塵埃上沉積不同柱密度的固態水分子，以檢驗碳基塵埃能提供的有效位點數量。結果顯示，在13 K時其有效位點的數量約為56.6-77.8 ML。;Recently, carbonaceous dust (C-dust) aroused the interest of scientists in the laboratory astrophysics/astrochemistry field as it can be seen as a potential carbon supplier for some complex organic molecules (COMs) or their precursors. Several studies have confirmed new formation routes of CO and CO2 from interactions between H2O ice and C-dust after the vacuum ultraviolet (VUV) irradiation (Mennella et al. 2006; Shi et al. 2015). However, none offered insights into the morphology of the ice-covered dust. Is all the ice buried in the dust, or only a few layers? According to Potapov et al. (2023), this question is crucial since the number of reactive sites can highly affect the production yield of those C-bearing products. Therefore, this study aimed to understand how temperature impacts the diffusion of water molecules into the C-dust and the subsequent number of effective sites. In this study, we deposited H2O ice at different temperatures ranging from 13 K to 150 K on the 13C-dust. Then, they were irradiated with VUV at 13 K. Our experiments showed that the production yield of 13C-products remains constant up to 100 K, with a value of around 0.006 molecules/photon, but increases significantly at temperatures above 100 K, reaching about 0.01 molecules/photon at 150 K. This highlights that the diffusion of H2O in the 13C-dust can influence the number of reactive sites, consequently affecting the production yield of 13C-products. Additionally, different column densities of H2O were deposited onto the 13C-dust to examine the number of effective sites provided by the 13C-dust. Results indicated that the effective site number of the 13C-dust is approximately 56.6-77.8 ML at 13 K.
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