Generation of Supra-molecular Cluster Structure and its Binding Condition

通过对液滴中分离的簇的质谱分析和完整溶液的x射线衍射测量，研究了x_E（乙醇摩尔分数）<或等于>0.2时乙醇-水二元溶液中簇的结构。在0.2<等于或小于等于>x_E<等于或小于等于>0.8的混合物中，乙醇-聚合物水合物（5<m<15）的平均水分子数（N^a）由水摩尔分数（x_w）的函数表示：Na^a={(m/4.2) -1} ^2 (x_w+0.85)，表明乙醇-聚合物水合物的基本结构在该区域是不变的。在x_3<约等于>0.2处发现N^a的拐点。x射线测量的径向分布函数（rdf）表明，随着x_E的增加，2.8 *处的线性氢键减少，而在0.4<小于等于>1.0时，最强的峰保持在4.8 *处。在质谱组成分析和RDFs浓度依赖性的基础上，我们提出了在0.2<小于等于>x_E<小于等于>0.8区域形成乙醇-水二元团簇的最可能模型。

The structure of clusters in ethanol-water binary solutions at x_E (ethanol mole fraction) <greater than or equal>0.2 is investigated by the mass spectrometric analysis of the clusters isolated from liquid droplets and X-ray diffraction measurements of intact solution. Average numbers of water molecules (N^a) of the ethanol m-mer hydrates (5<m<15) in the mixtures at 0.2<less than or equal>x_E<less than or equal>0.8 are found to be expressed by a function of water mole fraction (x_w) : Na^a={(m/4.2) -1} ^2 (x_w+0.85), suggesting that the fundamental structure of the ethanol polymer-hydrates is invariable in thie region. An inflection point of N^a was found at x_3<approximately equal>0.2. The radial distribution functions (RDFs) fromthe X-ray measurements demonstrated a decrease of linear hydrogen bonds at 2.8 * with increasing x_E, while keeping the strongest peak at 4.8 * in 0.4<less than or equal>x_E<less than or equal>1.0. On the basis of the composition analysis of the mass spectra and the concentration dependence of RDFs, we propose the most likely model of ethanol-water binary clusters formed in the region 0.2<less than or equal>x_E<less than or equal>0.8.