液态水中激光诱导等离子体产生的探测，这一成果由中科院北京凝聚态物理国家研究中心孟胜研究组经过不懈努力而取得。相关论文于2021年7月1日发表在《美国化学会杂志》上。

基于非绝热量子动力学模拟，研究组探索了液态水在强光激发下的飞秒演化。分离的离子和电子动力学被明确地监测，在前所未有的微观水平上揭示了巨大的细节。水被发现经历了两步加热过程。强场效应和电子激发是第一阶段加热和加压的主要原因。随后离子和电子子系统的驰豫进一步提高了离子温度，但释放了很大的内部压力。

在激光脉冲作用下，水分子被拉伸，电子激发导致了激光脉冲后的质子转移。强激光脉冲强烈激发液态水，在激光脉冲过程中产生严重的分子离解和等离子体。激光诱导的水等离子体具有高比例的自由质子(~50%)、非平衡离子和电子分布以及金属态电子密度等特征。

据悉，了解液态水的光激发动力学对于基础科学探索和技术应用都具有重要意义。尽管观测到了光诱导的宏观现象，但由于激光-水相互作用的极端复杂性和超快的时间尺度，很难跟踪激光照射后的初始原子运动和相关的能量转移路径。

附：英文原文

Title: Probing Laser-Induced Plasma Generation in Liquid Water

Author: Jiyu Xu, Daqiang Chen, Sheng Meng

Issue&Volume: July 1, 2021

Abstract: Understanding photoexcitation dynamics in liquid water is of crucial significance for both fundamental scientific exploration and technological applications. Despite the observations of photoinduced macroscopic phenomena, the initial atomistic movements and associated energy transfer pathways immediately following laser irradiation are hard to track due to the extreme complexity of laser–water interaction and its ultrafast time scale. We explore the femtosecond evolution of liquid water upon intense photoexcitation based on nonadiabatic quantum dynamics simulations. Separate ionic and electronic dynamics were explicitly monitored with tremendous details unveiled on an unprecedented microscopic level. Water was found to undergo the two-step heating processes. The strong-field effects and electronic excitations dominate the first-stage heating and pressurization. Subsequent relaxation of ionic and electronic subsystems further increases the ionic temperature but releases the large internal pressure. The water molecules are stretched during the laser pulses, and the electronic excitations result in the proton transfers after laser pulses. Intense laser pulses violently excite liquid water, giving rise to severe molecular dissociation and plasma generation during the laser pulses. The laser-induced water plasma is characterized by a high fraction of free protons (～50%), nonequilibrium ionic and electronic distributions, and a metallic electronic density of states.

DOI: 10.1021/jacs.1c04675

Source: https://pubs.acs.org/doi/10.1021/jacs.1c04675