X-ray spectroscopy studies of water and aqueous solutions

斯坦福大学的Anders Nilsson在实验物理化学计划的支持下，使用X射线吸收光谱（XAS）和X射线拉曼散射（XRS）来检查液态水和水溶液。 最近基于XAS和XRS对水的研究表明，液态水平均每个分子只有两个强氢键，而不是通常认为的约3.5个。 如果得到证实，这将极大地改变目前对水的结构及其在所涉及的许多过程中的作用的看法。 这里所采用的技术是基于使用内壳层电子从吸收/散射氧原子探测未占据的价电子结构，这取决于详细的分子排列。 该项目的一个重要方面是使用实验和密度泛函理论（DFT）计算相结合，以整合现有的水分子实验数据。 从这样的实验和理论的结合，水分子周围的局部氢键的协调可以探测与键伸长和角度扭曲的敏感性。 人们希望，这一关于水在不同热力学条件下的结构的新的独特信息将使人们能够理解水的许多不寻常性质的微观起源。 同样，水溶液中离子对水氢键网络的影响对于揭示水在化学和生物过程中的作用至关重要。水是我们在这个星球上生存的关键化合物，它参与了几乎所有的生物，地质和化学过程。 它已经被深入研究了数百年，但仍然令科学家感到困惑。 关于水中氢键网络结构的新知识对于理解其许多不寻常的化学和物理性质至关重要。 水研究预计将对媒体，公众和科学高中教师对化学的普遍兴趣产生广泛的影响。

Anders Nilsson of Stanford University is supported by the Experimental Physical Chemistry Program to use x-ray absorption spectroscopy (XAS) and x-ray Raman scattering (XRS) to examine liquid water and aqueous solutions. Recent studies of water based on XAS and XRS have suggested that liquid water has on average only two strong hydrogen bonds per molecule rather than ~3.5 as is commonly believed. If confirmed, this would dramatically change the current thinking about the structure of water and its role in the many processes in which it is involved. The techniques to be employed here are based on the use of inner shell electrons from the absorbing/scattering oxygen atom to probe the unoccupied valence electron structure, which depends in detail on the molecular arrangements. An important aspect of this project is to use a combination of experiments and density functional theory (DFT) calculations to integrate available experimental molecular data on water. From such a combination of experiment and theory, the local hydrogen-bonding coordination around water molecules can be probed with sensitivity to both bond elongations and angle distortions. It is hoped that this new unique information regarding the structure of water under different thermodynamic conditions will enable understanding of the microscopic origin of water's many unusual properties. Similarly, the influence of ions on the water hydrogen-bonding network in aqueous solutions is critical to unraveling the role of water in chemical and biological processes.Water is the key compound for our existence on this planet, and it is involved in nearly all biological, geological, and chemical processes. It has been studied intensively for hundreds of years but is still puzzling scientists. New knowledge about the hydrogen-bonded network structure in water is essential to understand its many unusual chemical and physical properties. Water research is expected to have a broad impact on general interest in chemistry in the media, general public, and for science high school teachers.