Infrared detection of (H2O)20 isomers of exceptional stability: a drop-like and a face-sharing pentagonal prism cluster.
Infrared detection of (H2O)20 isomers of exceptional stability: a drop-like and a face-sharing pentagonal prism cluster.
复制标题
DOI：
10.1039/c4cp03642e
复制
发表时间：
2014-11
期刊：
影响因子：
--
通讯作者：
C. C. Pradzynski-C.;Christoph W. Dierking;Florian Zurheide;Richard M. Forck;U. Buck;T. Zeuch;S. Xantheas
中科院分区：
文献类型：
--
作者：
C. C. Pradzynski-C.;Christoph W. Dierking;Florian Zurheide;Richard M. Forck;U. Buck;T. Zeuch;S. Xantheas
具有内部溶剂化水分子的水团簇是模拟凝聚相局部环境的广泛模型。稳定的(H2O)n团簇异构体的出现具有完全配位的内部分子，理论上预测出现在n=20的尺寸范围内。然而，我们目前关于这些结构在能量上变得更加稳定的大小区域的知识仍然是来自模拟的假设，而不是缺乏精确的大小分辨的实验测量。本文报道了用红外激发调制光电离光谱研究钠原子标记的(H2O)20团簇的尺寸和异构体选择红外光谱。在OH伸展区域观察到的吸收谱与理论预测的两种结构不同的异构体的光谱是一致的，这两种异构体是一个具有完全配位(内部)水分子的液滴状团簇和一个边缘共享的五角棱柱状团簇，其中所有原子都在表面上。这种水滴状结构是第一个实验检测到的水团，显示出在液态水中发现的局部连通性。
Water clusters with internally solvated water molecules are widespread models that mimic the local environment of the condensed phase. The appearance of stable (H2O)n cluster isomers having a fully coordinated interior molecule has been theoretically predicted to occur around the n = 20 size range. However, our current knowledge about the size regime in which those structures become energetically more stable has remained hypothetical from simulations in lieu of the absence of precisely size-resolved experimental measurements. Here we report size and isomer selective infrared (IR) spectra of (H2O)20 clusters tagged with a sodium atom by employing IR excitation modulated photoionization spectroscopy. The observed absorption patterns in the OH stretching region are consistent with the theoretically predicted spectra of two structurally distinct isomers of exceptional stability: a drop-like cluster with a fully coordinated (interior) water molecule and an edge-sharing pentagonal prism cluster in which all atoms are on the surface. The drop-like structure is the first experimentally detected water cluster exhibiting the local connectivity found in liquid water.