| The high-temperature and high-pressure environment created by strong pulse laser-induced shock waves provides a technological means for studying the dynamic behavior of materials under extreme conditions.Specifically,in liquid mediums,molecular dynamics become exceptionally complex in this environment.Aqueous solutions,crucial locations for biochemical reactions and detecting environmental changes,have garnered widespread attention.This paper explored the hydrogen bond structure and stimulated Raman scattering characteristics of water（heavy water）systems under the influence of strong laser-induced shock waves.Firstly,the impact of shock wave-induced high pressure on the hydrogen bond structure at the liquid water/heavy water-air interface was analyzed.It revealed the stimulated Raman scattering properties at the liquid water/heavy water-air interface,and we further investigated the effects of shock wave-induced resonance enhancement on the stimulated Raman scattering of liquid water/heavy water.Secondly,the paper analyzed the variations in the hydrogen bond network structure of liquid water/heavy water mixed solutions under extreme conditions induced by ion fields（LiOH）and acetone.（1）The stimulated Raman scattering behavior of the liquid water/heavy water-air interface under shock waves was studied.Through the stimulated Raman scattering spectra of the liquid water/heavy water-air interface,the distribution of water/heavy water Raman peaks at the interface and their enhancement mechanisms were explored.Low-frequency Raman shifts of O-H/O-D vibrations were observed in the stimulated Raman scattering of water/heavy water molecules at the interface.This phenomenon is attributed to laser-induced breakdown generating excess electrons,enhancing the nonlinear polarization of water/heavy water molecules,and promoting the intensity of characteristic Raman peaks.Meanwhile,the stimulated Raman scattering threshold at the water/heavy water-air interface is significantly lower than that inside the liquid,and the threshold shows an"N-shaped"curve relationship with distance.This is because the liquid interface acts as a reflector for the laser resonant cavity.The unique properties of the liquid-air interface play a crucial role in regulating the stimulated Raman scattering threshold.（2）Combining a stimulated Raman scattering generator and amplifier,the utilization of the resonance enhancement effect had effectively increased the intensity of cascaded stimulated Raman scattering and significantly lowered its threshold.The frequency difference between the pump light and stimulated Raman Stokes light matches the O-H/O-D stretching vibration frequency of water/heavy water molecules,leading to the loss of pump light and the enhancement of Stokes light.The time behavior of stimulated Raman scattering generation was explored,with Stokes light generated in the first half of the pump pulse.The study effectively eliminated the low-intensity extended tail,demonstrating pulse width compression capability.This research provides a new approach for high-intensity,tunable,broadband Raman lasers（3）The influence of shock waves on stimulated Raman scattering in LiOH-liquid water/heavy water solutions and the resulting changes in hydrogen bond structures were investigated.Analysis of stimulated Raman scattering spectra of mixed LiOH solutions at different concentrations revealed that at high concentrations,the Raman main peak of water/heavy water evolved into two or three characteristic peaks,significantly enhancing the normalized intensity of stimulated Raman scattering.The analysis of spontaneous Raman spectra indicated that LiOH enhanced the hydrogen bond network structure in liquid water/heavy water solutions,similar to the effect of applying pressure.This action increased the density of the liquid water/heavy water solution,prolonged the duration of laser-induced breakdown shock waves,slowed down the speed of shock waves,thereby increasing the compression effect caused by shock waves in liquid water/heavy water.（4）The dynamic behavior of hydrogen bond structures in acetone-water mixtures with and without shock waves was studied using spontaneous Raman and stimulated Raman scattering spectra.Firstly,in spontaneous Raman spectra without shock waves,with increasing volume fraction of acetone,the hydrogen bond network structure of water gradually strengthened but could lead to the destruction of the hydrogen bond structure at high volume fractions.Further analysis of stimulated Raman scattering spectra under shock wave compression was conducted by analyzing the Raman shifts and normalized intensities of O-H vibrations and C-H stretching peaks,obtaining volume fractions corresponding to hydrogen bond structure transitions.At low concentrations of acetone volume fraction,the carbonyl oxygen formed a complete tetrahedral hydrogen bond structure with neighboring four water molecules by H2O:（?）O=C compressing effect,enhancing the hydrogen bond structure of water.Additionally,the methyl group enhanced the hydrogen bond structure of water,forming a quasi-ice-like structure.However,as the concentration of acetone increased,the self-association of a large number of acetone molecules led to the destruction of the hydrogen bond structure of water,and the nonlinear changes in the acetone Raman peak validated the above conclusion. |
