School of Chemistry, University of Southampton, Southampton, SO17 1BJ, United Kingdom.
Phys Rev Lett. 2018 Jun 29;120(26):266001. doi: 10.1103/PhysRevLett.120.266001.
Water exists in two forms, para and ortho, that have nuclear spin states with different symmetries. Here we report the conversion of fullerene-encapsulated para water to ortho water. The enrichment of para water at low temperatures is monitored via changes in the electrical polarizability of the material. Upon rapid dissolution of the material in toluene the excess para water converts to ortho water. In H_{2}^{16}O@C_{60} the conversion leads to a slow increase in the NMR signal. In H_{2}^{17}O@C_{60} the conversion gives rise to weak signal enhancements attributed to quantum-rotor-induced nuclear spin polarization. The time constants for the para-to-ortho conversion of fullerene-encapsulated water in ambient temperature solution are estimated as 30±4 s for the ^{16}O isotopolog of water, and 16±3 s for the ^{17}O isotopolog.
水以两种形式存在，即具有不同对称性的顺式和反式，这里我们报告了富勒烯包裹的顺式水向反式水的转化。通过材料电极化率的变化来监测低温下顺式水的富集。将材料快速溶解在甲苯中，多余的顺式水会转化为反式水。在 H_{2}^{16}O@C_{60}中，这种转化导致 NMR 信号缓慢增加。在 H_{2}^{17}O@C_{60}中，这种转化导致了归因于量子转子诱导核自旋极化的弱信号增强。在环境温度溶液中，富勒烯包裹的水的顺式-反式转化的时间常数估计为 30±4 s，对于水的 ^{16}O 同位素，以及 16±3 s，对于水的 ^{17}O 同位素。
