Impact of nuclear quantum effects on the structural inhomogeneity of liquid water

作者：Arian Berger, Gustavo Ciardi, David Sidler, Peter M. Hamm, Andrey Shalit · 发表于：Proceedings of the National Academy of Sciences · 年份：2019 · DOI：10.1073/pnas.1818182116 · 被引用次数：53 · 研究领域：Spectroscopy and Quantum Chemical Studies、Quantum, superfluid, helium dynamics、Advanced NMR Techniques and Applications

The 2D Raman-terahertz (THz) response of liquid water is studied in dependence of temperature and isotope substitution ([Formula: see text]O, [Formula: see text]O, and [Formula: see text]O). In either case, a very short-lived (i.e., between 75 and 95 fs) echo is observed that reports on the inhomogeneity of the low-frequency intermolecular modes and hence, on the heterogeneity of the hydrogen bond networks of water. The echo lifetime slows down by about 20% when cooling the liquid from room temperature to the freezing point. Furthermore, the echo lifetime of [Formula: see text]O is [Formula: see text] slower than that of [Formula: see text]O, and both can be mapped on each other by introducing an effective temperature shift of [Formula: see text] K. In contrast, the temperature-dependent echo lifetimes of [Formula: see text]O and [Formula: see text]O are the same within error. [Formula: see text]O and [Formula: see text]O have identical masses, yet [Formula: see text]O is much closer to [Formula: see text]O in terms of nuclear quantum effects. It is, therefore, concluded that the echo is a measure of the structural inhomogeneity of liquid water induced by nuclear quantum effects.