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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Interaction of carboxylic acids and water ice probed by argon ion induced chemical sputtering
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Interaction of carboxylic acids and water ice probed by argon ion induced chemical sputtering

机译：氩离子诱导化学溅射探测羧酸与水冰的相互作用

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摘要

In this paper, we investigated the interaction of simple carboxylic acids, formic acid (FA), acetic acid (AA), and propionic acid (PA) with thin layers of water ice in the temperature range of 110-190 K in ultrahigh vacuum. The focus, however, is on the AA-ice system. Molecularly thin layers of these systems were prepared on a pre-cooled polycrystalline copper substrate. The interactions and phase changes in the system were monitored with chemical sputtering using low-energy (<= 30 eV) Ar+, which probes the topmost surface layers. At 110 K, the deposited AA exists as dimers in its amorphous solid form. At the same temperature, in the presence of water ice, this dimeric form gets converted to chainlike oligomers. Chemical sputtering spectra show distinct features for these two surface species. The data suggest that ion formation reflects the surface structure, implying a unique mechanism for its formation. Detailed studies have been made with amorphous solid water (ASW) and crystalline water (CW) to get a complete understanding of the system. Experiments carried out with AA-D2O ice confirmed the proton-transfer mechanism during chemical sputtering. Other studies were conducted with AA-CH3OH and AA-CCl4 systems. Detailed investigations performed to understand the effect of thickness of AA and ice overlayers suggest that the extent of water molecules required to effect the structural transformation in the acid is dependent on the amount of the latter. Dimeric-to-oligomeric transformation does not occur for the PA-ice system. Detection of a structural transition at the very top of ice in molecularly thin films adds additional capabilities to the low-energy ion scattering technique.
机译：在本文中，我们研究了简单的羧酸，甲酸（FA），乙酸（AA）和丙酸（PA）与薄冰层在110-190 K温度范围内在超高真空下的相互作用。但是，重点是AA-ice系统。这些系统的分子薄层是在预冷的多晶铜基板上制备的。使用低能量（<= 30 eV）Ar +的化学溅射监测系统中的相互作用和相变，该Ar +探测最顶层的表面层。在110 K下，沉积的AA以无定形固体形式以二聚体形式存在。在相同的温度下，在水冰的存在下，这种二聚体形式转化为链状低聚物。化学溅射光谱显示这两种表面物质的明显特征。数据表明离子形成反映了表面结构，这暗示了其形成的独特机理。已对非晶态固体水（ASW）和结晶水（CW）进行了详细研究，以全面了解该系统。用AA-D2O冰进行的实验证实了化学溅射过程中的质子转移机理。其他研究是使用AA-CH3OH和AA-CCl4系统进行的。为了解AA和覆冰层的厚度而进行的详细研究表明，影响酸中结构转变所需的水分子程度取决于后者的量。对于PA-ice系统，不会发生二聚体到低聚体的转化。检测分子薄膜中冰最顶部的结构转变为低能离子散射技术增加了更多功能。

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