A Fully Size-Resolved Perspective on the Crystallization of Water Clusters
A Fully Size-Resolved Perspective on the Crystallization of Water Clusters
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DOI：
10.1126/science.1225468
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发表时间：
2012-09-21
期刊：
影响因子：
56.9
通讯作者：
Buck, Udo
中科院分区：
文献类型：
--
作者：
Pradzynski, Christoph C.;Forck, Richard M.;Buck, Udo
事实证明，形成最小冰晶所需的水分子数量在实验上具有挑战性。这些信息将有助于更好地理解氢键相互作用，这些相互作用解释了水的宏观性质。在这里，我们报道了精确选择尺寸的(H2O)(N)团簇的红外光谱，n范围从85到475；钠掺杂和相关的红外激发调制光电离光谱允许研究这个以前难以处理的尺寸区域。当n=275+/-25时，首次观察到结晶开始的光谱特征；当n=475+/-25时，3200 cm(-1)左右的已知结晶冰带主导了OH-伸缩区。所应用的方法有可能将中性团簇的尺寸分辨红外光谱更广泛地推向100至1000分子范围，在该范围内，许多溶剂开始显示出凝聚相性质。
The number of water molecules needed to form the smallest ice crystals has proven challenging to pinpoint experimentally. This information would help to better understand the hydrogen-bonding interactions that account for the macroscopic properties of water. Here, we report infrared (IR) spectra of precisely size-selected (H2O)(n) clusters, with n ranging from 85 to 475; sodium doping and associated IR excitation-modulated photoionization spectroscopy allowed the study of this previously intractable size domain. Spectral features indicating the onset of crystallization are first observed for n = 275 +/- 25; for n = 475 +/- 25, the well-known band of crystalline ice around 3200 cm(-1) dominates the OH-stretching region. The applied method has the potential to push size-resolved IR spectroscopy of neutral clusters more broadly to the 100- to 1000-molecule range, in which many solvents start to manifest condensed phase properties.