Department of Chemistry, Rice University, Houston, Texas 77005, USA.
J Phys Chem B. 2012 Dec 13;116(49):14426-32. doi: 10.1021/jp310153n. Epub 2012 Dec 3.
Microscopic structures and dynamics of aqueous salt solutions were investigated with the ultrafast vibrational energy exchange method and anisotropy measurements. In KSCN aqueous solutions of various concentrations, the rotational time constants of SCN(-) anions are proportional to the viscosities of the solutions. However, the reorientation dynamics of the water molecules are only slightly affected by the solution viscosity. With the addition of strongly hydrated F(-) anions, the rotations of both SCN(-) anions and water molecules slow down. With the addition of weakly hydrated I(-) anions, only the rotation of SCN(-) anions slows down with that of water molecules unaffected. Vibrational energy exchange measurements show that the separation among SCN(-) anions decreases with the addition of F(-) and increases with the addition of I(-). The series of experiments clearly demonstrate that both structures and dynamics of ion and water are segregated in the strong electrolyte aqueous solutions.
采用超快振动能量交换方法和各向异性测量技术研究了水溶液中盐的微观结构和动力学。在不同浓度的 KSCN 水溶液中，SCN-阴离子的旋转时间常数与溶液的粘度成正比。然而，水分子的重取向动力学仅受溶液粘度的轻微影响。随着强水合 F-阴离子的加入，SCN-阴离子和水分子的旋转都减慢。随着弱水合 I-阴离子的加入，只有 SCN-阴离子的旋转减慢，而水分子的旋转不受影响。振动能量交换测量表明，随着 F-的加入，SCN-阴离子之间的分离减少，而随着 I-的加入，SCN-阴离子之间的分离增加。一系列实验清楚地表明，在强电解质水溶液中，离子和水的结构和动力学是分离的。
