发表机构
Aix Marseille Univ, CNRS, CINaM; Center for Interstellar Catalysis (InterCat), IFA, Aarhus University（艾克斯-马赛大学，法国国家科学研究中心，纳米科学与材料中心; 奥胡斯大学物理研究所，星际催化中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究以CO为原型，结合多种技术揭示纳米级表面形态调控低温下气体在尘埃颗粒上的粘附与冻结，修正了重物质粘附概率接近1的假设，明确纳米级形态降低有效粘附概率的机制。
AI 中文摘要
在冷分子云中，气体在尘埃颗粒上的冻结启动了星际冰的形成，但通常假设低温下重物质的粘附概率接近1。近期对真实尘埃颗粒类似物的实验室测量表明，这一假设可能不成立。以一氧化碳（CO）为原型，我们研究了10 K下纳米级表面形态如何控制高定向热解石墨和碳烟上的吸附与冰生长。我们结合X射线光电子能谱、低温扫描隧道显微镜（STM）、动力学蒙特卡洛模拟及热力学描述，将分子滞留与局部表面结构关联起来。CO在石墨上并非以单位粘附量吸附：吸附过程经历单层生长、单层完成附近的低滞留转变以及延迟的多层生长。STM显示CO在石墨平台上仍具有高迁移性，主要在岛边缘和平台台阶处稳定。在碳烟上，相同序列在高得多的曝光量下发生，且粘附系数显著更低，模拟显示凹区域优先滞留，凸状粗糙处润湿性差。这些结果表明，低温粘附由撞击后的探索以及稳定与逃逸之间的竞争所控制。纳米级形态放大了该机制，降低了真实尘埃颗粒上的有效粘附概率并延迟了气体冻结。
英文摘要
In cold molecular clouds, gas freeze-out onto dust grains initiates interstellar ice formation, yet sticking probabilities of heavy species are often assumed to be near unity at low temperature. Recent laboratory measurements on realistic grain analogues show that this assumption can fail. Using CO as a prototype, we investigate how nanoscale surface morphology controls adsorption and ice growth at 10 K on highly oriented pyrolytic graphite and carbon soot. X-ray photoelectron spectroscopy, low-temperature scanning tunneling microscopy, kinetic Monte Carlo simulations, and a thermodynamic description are combined to relate molecular retention to local surface structure. CO does not adsorb with unit sticking on graphite: adsorption proceeds through monolayer growth, a reduced-retention crossover near monolayer completion, and delayed multilayer growth. STM shows that CO remains highly mobile on graphite terraces and is stabilized mainly at island edges and terrace steps. On soot, the same sequence occurs at much higher exposures and with substantially lower sticking coefficients, while simulations show preferential retention in concave regions and poor wetting of convex asperities. These results indicate that low-temperature sticking is governed by post-impact exploration and competition between stabilization and escape. Nanoscale morphology amplifies this mechanism, reducing effective sticking probabilities and delaying gas freeze-out on realistic dust grains.
Comments12 pages, 13 figures
