Extreme-ultraviolet Photochemistry in Water-covered Carbonaceous Dust analogs: Effects of Dust Thickness and Hydrogen Content
The Astrophysical Journal 1004 (2026) 181
Chun-Yi Lee, Ko-Yu Chuang, Yen-Yu Hsu, Cornelia Jäger Thomas Henning, and Yu-Jung Chen
Extreme-ultraviolet Photochemistry in Water-covered Carbonaceous Dust analogs: Effects of Dust Thickness and Hydrogen Content
本研究在探討不同厚度的氫化與非氫化無序碳塵埃與水冰(H2O ice)在極紫外光照射下的光化學生成效率差異，研究團隊透過國際合作，初期前往德國機構利用雷射剝蝕法製備類星塵碳塵埃樣品，隨後與荷蘭合作夥伴共同申請國家同步輻射中心的極紫外光波段光源進行模擬實驗。團隊藉由紅外吸收光譜即時監測13C碳塵埃與水冰介面反應生成的13CO2 變化趨勢，並透過類一階反應模型定量評估光化學效率。研究結果證實13CO2的生成效率在氫化與非氫化碳塵埃皆與其塵埃厚度成正比；同時由於含氫碳塵埃上具有額外的反應位點，使其在相同塵埃厚度情況下的反應效率顯著優於非氫化樣品。這項成果不僅提供了一條可在相對高溫之宇宙環境中進行的非傳統CO2生成機制，也成功解釋了氫化碳塵埃與冰晶交互作用的高活性。
This study investigates the interfacial reaction on the water-covered carbonaceous dust, including amorphous carbon and hydrogenated amorphous carbon, under extreme ultraviolet (EUV) irradiation. Through an international collaboration, the research team initially prepared carbonaceous dust analogues using laser ablation at a partner institution in Germany, and subsequently performed the experiments within cosmic-environment at the National Synchrotron Radiation Research Center (NSRRC) with collaborators from the Netherlands. By using Fourier-transform infrared (FTIR) spectroscopy to monitor the evolution of 13CO2 produced at the ice-dust interface, the team applied a pseudo-first-order reaction model to quantify the photochemical efficiencies. The results reveal that while the 13CO2 production rate scales linearly with dust thickness for both dust types and the hydrogenated samples benefit from additional reaction sites on their surfaces. These findings not only provide an alternative pathway for CO2 formation in relatively warm cosmic environments but also successfully explain the enhanced reactivity of hydrogenated carbon dust in interstellar ice chemistry.