Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron, DE-22607 Hamburg, Germany.
Department of Physics and Astronomy, Uppsala University, SE-751 20 Uppsala, Sweden.
Proc Natl Acad Sci U S A. 2018 May 29;115(22):5652-5657. doi: 10.1073/pnas.1711220115. Epub 2018 May 14.
The bright ultrafast pulses of X-ray Free-Electron Lasers allow investigation into the structure of matter under extreme conditions. We have used single pulses to ionize and probe water as it undergoes a phase transition from liquid to plasma. We report changes in the structure of liquid water on a femtosecond time scale when irradiated by single 6.86 keV X-ray pulses of more than 10 J/cm These observations are supported by simulations based on molecular dynamics and plasma dynamics of a water system that is rapidly ionized and driven out of equilibrium. This exotic ionic and disordered state with the density of a liquid is suggested to be structurally different from a neutral thermally disordered state.
X 射线自由电子激光的明亮超短光脉冲允许在极端条件下研究物质的结构。我们使用单个光脉冲在水经历从液态到等离子态的相变时对其进行电离和探测。我们报告了当用超过 10 J/cm 的单个 6.86 keV X 射线脉冲辐照时，液体水的结构在飞秒时间尺度上的变化。这些观察结果得到了基于分子动力学和水系统等离子体动力学的模拟的支持，该系统被快速电离并驱离平衡。这种具有液体密度的奇特离子无序状态在结构上被认为与中性热无序状态不同。
