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Stimulated Raman scattering (SRS) not only expands the spectral range of stimulated emission but also presents a way to delve into the intricate microscopic dynamics of matter. In this manuscript, SRS of O–O and O–H stretching vibrations in H2O–H2O2 solution is measured using 532 nm Nd:YAG laser. SRS peak intensities of O–O and O–H stretches are observed to engage in a competitive process, depending on the coupling direction of the excess electrons, which is determined by the recombination rate of H2O2 and H2O under laser-induced breakdown. Notably, a high-order (fifth order) SRS peak originating from H2O2 is detected, attributable to the Raman-active enhancement caused by surplus electrons and the amplification of vibration energy resulting from shockwaves. This experiment holds potential for advancing multi-wavelength selective regulation in terms of its contributions. [ABSTRACT FROM AUTHOR]

Forward stimulated Raman scattering in pure water and H2O2–H2O mixture solutions are investigated under different pump laser energies. Three characteristic peaks are observed in mixture solutions due to the enhancement of hydrogen bonds (H‐bonds) structure of water molecules by H2O2. Simultaneously, stimulated Raman scattering lines indicate that high‐pressure ice‐phase is formed in mixture solutions, which is attributed to the reduction of the laser breakdown threshold of liquid water by H2O2, resulting in a strong dynamic high pressure. [ABSTRACT FROM AUTHOR]

Liquid water is a complex system consisting of ice‐like and quartz‐like structure based on the classic two‐state model. Although lots of theoretical work have been developed about this model, the experimental evidences are still needed. Herein, a 355‐nm pulse laser is employed to excite stimulated Raman scattering (SRS) of liquid water both in bulk and on surface, with the generation of shockwave‐induced dynamic high pressure. Two characteristic features Raman peaks of both spontaneous Raman and SRS indicate the coexistence of two structures in localized water area. The ice‐like structure corresponds to ice Ih phase under the presented conditions, because the pressure dependence behavior of Raman shift agree well with the anomaly of diffusion coefficient of ice Ih phase, when the shock wave‐induced dynamic high pressure forms. Two structures show different pressure‐dependent behaviors based on the SRS results; meanwhile, the distribution of two structures is different in bulk and on surface water. [ABSTRACT FROM AUTHOR]

Stimulated Raman scattering (SRS) in H2O2–H2O mixture solutions are obtained in forward and backward directions. Characteristic features peaks related to OH stretching vibrations of water are the appearance of three enhancement peaks in both directions. Simultaneously, the low‐wavenumber SRS peaks in water at 840 and 1,700 cm−1 are enhanced. The mechanism of enhancement is attributed to excess electron‐enhanced Raman scattering. The electron‐enhanced process is also discussed. [ABSTRACT FROM AUTHOR]

Stimulated Raman scattering (SRS) spectra of the OH stretching vibrations of pure water and 2‐nm Si quantum dots (Si QDs) water solution have been investigated under different pump laser energies. Simultaneously, we have studied the spontaneous Raman spectra of pure water and Si QDs water solution at room temperature and atmospheric pressure. The results show that SRS intensity of Si QDs water solution is an order of magnitude higher than that of pure water at the same laser energy, which indicates that Si QDs enhance the SRS intensity of water molecules. The QDs enhancement SRS mechanism is attributed to the increase of third‐order nonlinear Raman susceptibility from the electric fields induced by the exciton effect of Si QDs. Stimulated Raman scattering (SRS) intensity of Si quantum dots (Si QDs) water solution is an order of magnitude higher than that of pure water.The increase of the third‐order nonlinear polarizability in water molecules is induced from the exciton effect of Si QDs.Due to Si QDs having a self‐absorption effect, the most obvious enhancement effect appears at laser energy of 110 mJ. [ABSTRACT FROM AUTHOR]

Stimulated Raman scattering (SRS) of water molecules excited by 532 nm laser is greatly enhanced by the application of CW (continuous-wave) seeding laser with 650 nm. When the CW laser power is 1 mW, the normalized SRS intensity of O–H stretching vibration at 3405 cm−1 is increased by ten orders of magnitude. Two new lower frequency shoulder peaks are also observed after adding CW seeding laser, which shift to the low-wavenumber due to the pulse heating of water molecules in the laser focused volume. The CW seeding laser not only lowers the threshold of SRS, but also increases the intensity of SRS. The mechanism of enhancement is attributed to the frequency difference between pump laser (532 nm) and CW seeding laser (650 nm) matching the O–H stretching vibrational frequency of water molecule, which provides the possibility of using resonance methods to enhance weak Raman vibration modes. • CW seeding laser lowers the threshold of SRS, but increases the intensity of SRS. • Frequency difference of two lasers matches O–H stretching vibrational frequency. • Resonance effect enhances Raman vibration modes in water. [ABSTRACT FROM AUTHOR]

Stimulated Raman scattering of ethanol-water binary solutions is investigated when an intense pulsed beam is focused on sample solutions. Two new enhanced peaks of water at about 3300 and 3375 cm−1 are obtained in dilute ethanol solutions (Volume Ratio of ethanol: V E from 0 to 0.1), indicating the formation of strong hydrogen bonds, which results from the cooperation of the hydroxyl-enhanced hydrogen bonds and the ice-like structure around the ethyl groups. However, when V E increases to 0.2, the main peak of water is very weak and a new peak appears at 3500 cm−1, indicating the destroy of hydrogen bonds network structure, which is attributed to the self-association in ethanol aggregates. Unlabelled Image • When the volume ratio of ethanol (V E) < 0.2, the hydrogen bonds structure of water is enhanced. • The peak at 3300 cm−1 represents the ice-like structure. • Self-association of ethanol (V E > 0.2) destroys hydrogen bonds network of water. [ABSTRACT FROM AUTHOR]