星际冰在碳质尘埃上的分子特异性扩散与脱附
Molecule-specific diffusion and desorption of interstellar ices on carbonaceous dust
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中文总结 AI 辅助
通过实验室研究发现，星际冰在碳质尘埃上的扩散与脱附具有分子特异性，尘埃-冰界面会影响冰的结构和脱附动力学，为天文观测和星际冰化学模型提供了新约束。
中文摘要 AI 辅助
星际冰形成于分子云最冷区域的尘埃颗粒上，保存着关键的挥发物储库，可能在恒星和行星形成过程中被纳入原行星盘。然而，尘埃表面组成对冰结构和光谱行为的影响仍知之甚少。我们开展了一项天体物理相关冰（CO、CO₂和H₂O）的对比实验室研究，这些冰沉积在惰性氟化钙（CaF₂）基底和碳质尘埃模拟物上，实验处于星际条件下。红外光谱和程序升温脱附显示，无定形碳质表面对红外光谱响应具有显著的分子特异性：CO和CO₂均呈现吸收带增宽、带位置红移以及脱附延迟，这源于热激活的扩散进入多孔尘埃基质，表明存在强分子-表面相互作用；相比之下，H₂O的光谱和热行为仅发生极小变化，表明其润湿性弱，与基底的耦合有限。这些结果提供了直接的实验室证据，证明即使在厚冰层中，尘埃-冰界面也能影响星际冰的结构和脱附动力学。这些发现为解释天文观测中的红外吸收带提供了新的约束，并强调了表面效应在星际冰化学模型中的重要性。
英文摘要
Interstellar ices form on dust grains in the coldest regions of molecular clouds and preserve key volatile reservoirs that could be incorporated into protoplanetary disks during star and planet formation. However, the effect of the dust surface composition on the ice structure and spectroscopic behavior remains poorly constrained. We present a comparative laboratory study of astrophysically relevant ices (CO, CO2, and H2O) deposited on inert calcium fluoride (CaF2) substrate and carbonaceous dust analogs under interstellar conditions. Infrared spectroscopy and temperature-programmed desorption reveal pronounced molecule-specific infrared spectral responses to the amorphous carbonaceous surface. CO and CO2 both exhibit broadened absorption bands, redshifted band positions, and delayed desorption, arising from thermally activated diffusion into the porous dust matrix and indicating strong molecule-surface interactions. By contrast, H2O varies only very little spectrally and thermally, indicating weak wetting and limited coupling to the substrate. These results provide direct laboratory evidence that dust-ice interfaces can affect the ice structure and desorption kinetics of interstellar ices even in thick ice layers. These findings offer new constraints for interpreting infrared absorption bands in astronomical observations and highlight the importance of surface effects in models of interstellar ice chemistry.
