Supercooled water structures Water displays a number of anomalous properties that are further enhanced in its supercooled state, but experimental studies at ambient pressure must obtain data before the onset of rapid crystallization at temperatures below ∼240 kelvin. Kringle et al. obtained infrared spectra of supercooled water films at temperatures between 135 and 235 kelvin that formed for a few nanoseconds by ultrafast heating and cooling. Supercooled water thermally equilibrates before crystallization above 170 kelvin, and over the range of temperatures studied, the structure of water was shown to be a linear combination of a high-density and a low-density liquid. Science, this issue p. 1490 Infrared spectroscopy reveals a temperature-dependent mixture of two local structural motifs in films of supercooled water. A fundamental understanding of the unusual properties of water remains elusive because of the limited data at the temperatures and pressures needed to decide among competing theories. We investigated the structural transformations of transiently heated supercooled water films, which evolved for several nanoseconds per pulse during fast laser heating before quenching to 70 kelvin (K). Water’s structure relaxed from its initial configuration to a steady-state configuration before appreciable crystallization. Over the full temperature range investigated, all structural changes were reversible and reproducible by a linear combination of high- and low-temperature structural motifs. The fraction of the liquid with the high-temperature motif decreased rapidly as the temperature decreased from 245 to 190 K, consistent with the predictions of two-state “mixture” models for supercooled water in the supercritical regime.

中文翻译：

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过冷液态水从 135 到 245 K 的可逆结构转变

过冷水结构 水显示出许多异常性质，在其过冷状态下会进一步增强，但在环境压力下进行的实验研究必须在低于 240 开尔文的温度下开始快速结晶之前获得数据。克林格尔等人。获得了温度在 135 到 235 开尔文之间的过冷水膜的红外光谱，该膜通过超快加热和冷却形成了几纳秒。过冷水在 170 开尔文以上结晶之前达到热平衡，并且在研究的温度范围内，水的结构显示为高密度和低密度液体的线性组合。科学，这个问题 p。1490 红外光谱揭示了过冷水薄膜中两种局部结构基序的温度相关混合物。由于在相互竞争的理论之间做出决定所需的温度和压力数据有限，因此对水的异常性质的基本理解仍然难以捉摸。我们研究了瞬态加热过冷水膜的结构转变，在淬火到 70 开尔文 (K) 之前，在快速激光加热过程中，每脉冲演变了几纳秒。在明显的结晶之前，水的结构从其初始配置松弛到稳态配置。在研究的整个温度范围内，通过高温和低温结构基序的线性组合，所有结构变化都是可逆和可重复的。随着温度从 245 K 降低到 190 K，具有高温基序的液体比例迅速下降，