Waluyo Iradwikanari, Nordlund Dennis, Bergmann Uwe, Schlesinger Daniel, Pettersson Lars G M, Nilsson Anders
Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, P.O. Box 20450, Stanford, California 94309, USA.
Linac Coherent Light Source, SLAC National Accelerator Laboratory, P.O. Box 20450, Stanford, California 94309, USA.
J Chem Phys. 2014 Jun 28;140(24):244506. doi: 10.1063/1.4881600.
X-ray absorption spectroscopy measured in transmission mode was used to study the effect of alkali and halide ions on the hydrogen-bonding (H-bonding) network of water. Cl(-) and Br(-) are shown to have insignificant effect on the structure of water while I(-) locally weakens the H-bonding, as indicated by a sharp increase of the main-edge feature in the x-ray absorption spectra. All alkali cations act as structure-breakers in water, weakening the H-bonding network. The spectral changes are similar to spectra of high density ices where the 2nd shell has collapsed due to a break-down of the tetrahedral structures, although here, around the ions, the breakdown of the local tetrahedrality is rather due to non-directional H-bonding to the larger anions. In addition, results from temperature-dependent x-ray Raman scattering measurements of NaCl solution confirm the H-bond breaking effect of Na(+) and the effect on the liquid as similar to an increase in temperature.
采用透射模式测量的X射线吸收光谱来研究碱金属离子和卤离子对水的氢键网络的影响。结果表明，Cl(-)和Br(-)对水的结构影响不显著，而I(-)会局部削弱氢键，这表现为X射线吸收光谱中主边缘特征的急剧增加。所有碱金属阳离子在水中都起到结构破坏者的作用，会削弱氢键网络。光谱变化与高密度冰的光谱相似，在高密度冰中，由于四面体结构的破坏，第二配位层已经坍塌，不过在这里，在离子周围，局部四面体性的破坏主要是由于与较大阴离子的非定向氢键作用。此外，NaCl溶液的温度依赖性X射线拉曼散射测量结果证实了Na(+)的氢键破坏作用以及对液体的影响，这种影响类似于温度升高的影响。
