Theoretical Chemistry Institute and Department of Chemistry, University of Wisconsin, Madison, WI 53706, USA.
Proc Natl Acad Sci U S A. 2013 Feb 5;110(6):1992-8. doi: 10.1073/pnas.1222017110. Epub 2013 Jan 17.
Using our newly developed explicit three-body (E3B) water model, we simulate the surface of liquid water. We find that the timescale for hydrogen-bond switching dynamics at the surface is about three times slower than that in the bulk. In contrast, with this model rotational dynamics are slightly faster at the surface than in the bulk. We consider vibrational two-dimensional (2D) sum-frequency generation (2DSFG) spectroscopy as a technique for observing hydrogen-bond rearrangement dynamics at the water surface. We calculate the nonlinear susceptibility for this spectroscopy for two different polarization conditions, and in each case we see the appearance of cross-peaks on the timescale of a few picoseconds, signaling hydrogen-bond rearrangement on this timescale. We thus conclude that this 2D spectroscopy will be an excellent experimental technique for observing slow hydrogen-bond switching dynamics at the water surface.
我们使用新开发的显式三体 (E3B) 水模型来模拟液态水的表面。我们发现，表面氢键切换动力学的时间尺度比体相中的要慢大约三倍。相比之下，在该模型中，表面的旋转动力学比体相中的稍快。我们将二维（2D）和频产生（2DSFG）光谱学作为一种观察水表面氢键重排动力学的技术。我们计算了两种不同偏振条件下的非线性极化率，在每种情况下，我们都在几皮秒的时间尺度上观察到了交叉峰的出现，这表明在这个时间尺度上氢键发生了重排。因此，我们得出结论，这种 2D 光谱学将是观察水表面慢氢键切换动力学的一种极好的实验技术。
