Efficient generation of multi-order Raman radiation in aqueous solutions derived from -CH and -NH vibrations via cascaded four-wave mixing and Stokes processes.

Multiple coherent radiations are achieved in a water-3-aminopropanol (3AP) mixed solution through cascaded four-wave mixing (C-FWM) and cascaded Stokes (C-Stokes) processes, both driven by stimulated Raman scattering (SRS) in this work. The O-H vibration peak from water is replaced by the emergence of the -NH symmetric stretching Raman peaks from 3AP, with intensity approaching that of the -CH symmetric stretching peak. The dual-wavelength SRS signals for the -NH and -CH stretching vibrations have a relatively small frequency interval of about 400 cm (16 nm).

Stimulated Raman scattering and enhancement mechanisms in alkali metal hydroxide aqueous solutions under laser-induced dynamic pressure.

Stimulated Raman scattering (SRS) in lithium hydroxide-water/heavy water (LiOH-HO/DO) solutions with varying concentrations was investigated under laser-induced high-pressure conditions using an Nd: YAG laser. The spectra revealed a significant enhancement in SRS signals, characterized by the emergence of low-wavenumber Raman peaks and a shift of the main SRS peak of liquid water to lower frequencies, evolving from a single peak to two or three peaks, which suggested the formation of an ice-like structure. Additionally, the normalized SRS intensity was higher than that of pure water.

Pressure-induced hydrogen bonding modulating Fermi resonance between fundamental modes in xylitol molecule.

Xylitol, as a typical polyol, has a broad range of application prospects. However, the molecular states of xylitol under different environments are rarely reported until now. In this work, the state changes of xylitol molecules under high pressure were analyzed by Raman spectra.

DMSO synergized with sugars: optical clearing agent modulation of optical coherence tomography of skin tissues.

The stratum corneum of the outermost skin is an important barrier impeding transdermal permeation, and permeation enhancers can reduce the barrier resistance of the stratum corneum and enhance the permeation of drugs in tissues. The optical imaging depth, signal intensity, and scattering coefficient variation rules of skin tissues in time dimension are obtained by using optical coherence tomography (OCT). The effect of optical clearing agents (OCAs) on OCT imaging is obtained by quantitatively analyzing the changes in the optical properties of tissues.

Investigating local field tuning Fermi resonance of CS by Raman spectroscopy and DFT calculations.

In the spectroscopic study of polyatomic molecules, Fermi resonance (FR) is a vibrational coupling and energy transfer phenomenon that widely exists intra- and intermolecular. In particular, the FR coupling between the fundamental mode ν and the doubling mode 2ν of the CS molecule has attracted extensive research. In this work, we investigate the effect of local field on tuning the FR of CS.

Exploring the dynamic changes in hydrogen bond structure of water and heavy water under external perturbation of DMF.

The Raman spectra of DMF-water/heavy water binary solutions at different volume ratios are measured to investigate the hydrogen bond structure between N, N-dimethylformamide (DMF) and water/heavy water. It was observed that when V below 40 %, DMF reinforces the hydrogen bond among water molecules through the substitution of a small amount of water molecules within the tetrahedral structure. However, a similar enhancement phenomenon is not observed in heavy water.

Enhancement of stimulated Raman scattering of a weak vibration mode in tetrahydrofuran through the energy-transfer resonance of lycopene.

A method of energy-transfer resonance of lycopene used to enhance stimulated Raman scattering (SRS) of a weak vibration C-O mode in tetrahydrofuran (THF) was developed in this study. Only C-H SRS was observed in pure THF at high energies. When lycopene was added, the C-O SRS located at 915 cm of the weak vibration mode in THF was observed.

Cationic complex-enhanced C-H stimulated Raman scattering in naphthalene-benzene solution.

Ring skeleton vibrations of aromatic series are dominant in Raman spectroscopy compared with the C-H stretching vibrations. When a laser-induced plasma (LIP) was generated in a mixed solution of naphthalene and benzene, an anomalous enhancement was observed in stimulated Raman scattering (SRS) of aromatic C-H stretching vibrations of naphthalene (3055 cm). However, SRS of C-H stretching vibrations of benzene at 3060 cm disappeared.

Pressure-induced Fermi resonance between fundamental modes in α-Hydroquinone.

Fermi resonance (FR), a prevalent phenomenon in molecules, has an important effect in spectrum analysis. As an effective way to change the molecular structure and tune symmetry, high-pressure techniques can often induce FR. Hydroquinone (HQ) is a hydrogen-bonded crystal that tends to form a solid inclusion compound with a suitable guest and has wide applications.

Temperature dependence of stimulated Raman scattering from a VYO crystal.

The microstructural, electrical, and optical properties of crystals are critical to laser device performance, and the temperature-dependence effect of crystals has gained a great deal of attention in research. The linewidth, stimulated Raman scattering (SRS) shift, and intensity of the characteristic peak at 890 cm of YVO crystal have been investigated between 148 and 448 K. As the crystal temperature increases, the bond length increases and the crystal force constant decreases, and the phonon softening process arises in the crystal at high temperature.

Exploring electronic energy level structure and excited electronic states of β-carotene using DFT.

Carotenoids are a class of natural pigments that play a fundamental role in photosynthesis and optoelectronics. However, the complexity of their energy level structure and electronic states has prevented a clear interpretation of their photophysics and photochemistry. The mediating nonradiative decay of the bright S state to the dark S state of carotenoids involves a population of bridging intermediate state.

Intermolecular energy transfer-enhanced super-broadband stimulated Raman scattering in cyclohexane-benzene mixtures.

Supercontinuum radiation has found numerous applications in diverse fields encompassing spectroscopy, pulse compression, and tunable laser sources. Anomalous enhanced stimulated Raman scattering (SRS) of cyclohexane-benzene mixtures was obtained in this study. SRS of the pure solvent, the multi-order Stokes of the strongest fundamental vibration modes, and energy transfer in intra-molecular modes were observed.

Hydrogen bond network dynamics of heavy water resolved by alcohol hydration under an intense laser.

Despite a great deal of effort spanning for decades, it remains yet puzzling concerning how alcohol molecules functionalize the hydrogen bond (H-bond) networks of water. We employed an isotopic substitution method (using alcohol-heavy water system) to avoid spectral overlap between the alcohol hydroxyl groups and water hydrogen bonds. We showed spectrometrically that under the strong pulse laser, the low mixing ratio (V < 20%) of alcohol can strengthen the H-bond network structure of DO through :ÖCH↔ DÖ: compression.

Hydrogen-Bond Dynamics and Water Structure in Aqueous Ethylene Glycol Solution via Two-Dimensional Raman Correlation Spectroscopy.

The hydrogen-bond (H-bond) dynamics and water structural transitions in aqueous ethylene glycol (EG) solution were investigated on the basis of concentration- and temperature-dependent two-dimensional Raman correlation spectroscopy (2D Raman-COS). At room temperature, EG-induced enhancement of the water structure when the EG/water molar ratio is less than 1:28 resulted from the hydrophobic effect around the methylene groups of EG. The decrease in the temperature caused an enhancement of the Raman peak at about 3200 cm, representing an increase in the orderliness of water molecules.

Tuning the Fermi resonance of pyridine using ethanol molecules.

The Fermi resonance (FR) phenomenon is prevalent in infrared and Raman spectroscopy, and it can be observed in a variety of molecules. In particular, pyridine is a compound that has two Fermi doublets: ν ∼ ν and ν + ν ∼ ν. To analyze the effect of environmental changes on the FR, this study first investigated the Raman spectra of pyridine mixed with ethanol at different concentrations.

Investigated hydrogen-bond network kinetics of acetone-water solutions by spontaneous and stimulated Raman spectroscopy.

The hydrogen bond (HB) network structure and kinetics of the acetone-water mixed solutions were investigated by the spontaneous Raman and stimulated Raman scattering (SRS) spectra. The HB network of water molecules was enhanced when the volume fraction of acetone ranged from 0 to 0.25.

Generation of dual-supercontinuum coherent radiation in acetone mixed with carbon disulfide by stimulated Raman scattering.

Stimulated Raman scattering (SRS) in a liquid has been a major focus of nonlinear optics. Traditional SRS generates single or cascaded Stokes components arising from spontaneous Raman noise. Herein, we report the formation mechanism of a specific spectrum-continuous spectroscopy technique based on SRS of mixed liquids.

Hydrogen bonding network dynamics of 1,2-propanediol-water binary solutions by Raman spectroscopy and stimulated Raman scattering.

Raman spectroscopy and stimulated Raman scattering (SRS) were used to investigate the hydrogen bonding (HB) network in 1,2-propanediol (1,2-PD)-water binary solutions. Abnormal changes in hydrogen bonds (HBs) were detected when V (volume fraction of the1,2-PD) was 0.4.

Modulated excited state geometry and Electron-Phonon coupling of lutein by temperature and solvent polarizability.

Resonance Raman spectroscopy is one of the spectroscopic methods often chosen for studying linear polyene molecules because the Raman intensities of their υ (C = C) and υ (C-C) stretching vibrations are sensitive to electron-phonon coupling and the π-electron energy gap. Here, the resonance Raman and absorption spectra of lutein were studied as a function of solvent polarizabilities and of temperature in the CS solvent. For lutein in CS, as the temperature decreased and CS solidified, the Raman scattering cross-section (RSCS) and the electron-phonon coupling constant had opposite dependence trends on temperature.

Coherent Raman comb generation in HOaqueous solutions by crossing-pump stimulated Raman scattering.

The cascaded stimulated Raman scattering (SRS) of 30% HO aqueous solutions was investigated using a pulsed Nd: YAG laser with a wavelength of 532 nm. The transfer of excess electrons between HO and HO molecules enhanced the SRS. Together, the decomposition of HO and the intense SRS Stokes led to the generation of the crossing-pump effect of HO aqueous solutions and the appearance of a new peak at 4229 cm that is excited by Stokes as the pump source.

Investigated coherent anti-Stokes Raman scattering in the process of cascaded stimulated Raman scattering in liquid and ice-Ih DO.

Stimulated Raman scattering (SRS) of liquid and ice-Ih DO was investigated using a pulsed Nd:YAG laser with a wavelength of 532 nm. The high-order Stokes peaks and corresponding anti-Stokes SRS [Coherent Anti-Stokes Raman Spectroscopy (CARS)] peaks were obtained. Two symmetric and antisymmetric Raman modes of stretching vibrations were observed in liquid DO, while only a symmetric stretching vibration mode was observed in ice-Ih DO.

Short-pulse broadband stimulated Raman scattering in carbon disulfide via resonance cascading.

Cascaded stimulated Raman scattering (SRS) of carbon disulfide () was investigated by a pulsed Nd:YAG laser with a wavelength of 532 nm. The fourth-order Stokes and second-order anti-Stokes lines were generated when the pump laser energy was about 1.909 mJ in one sample cell () only.

Determination of temperature-dependent Fermi resonance in acetonitrile-water binary solution by two-dimensional correlation Raman spectroscopy.

Acetonitrile (AN), as an organic solvent, has a wide range of applications. The C≡N stretching vibration mode (ν) and the combination mode (ν + ν) are coupled by Fermi resonance (FR). In this work, the phase transition and the interaction mechanism of the 60% AN-water binary solution (AN-Water) were analyzed by calculating FR parameters and two-dimensional correlation Raman spectroscopy (2DCRS).

Intramolecular Vibration Energy-Transfer-Driven Cascaded Stimulated Raman Scattering and Four-Wave Mixing in Benzene Series.

Cascaded stimulated Raman scattering (SRS) of benzene, bromobenzene, chlorobenzene, ethylbenzene, and toluene was investigated by a pulsed Nd:YAG laser with 532 nm wavelength. The results showed that the third-order Stokes SRS of the ring skeleton vibration (CC at 3006 cm) accompanied by another higher-frequency Stokes SRS of the CH stretching vibration (at 3066 cm), which arose only when the third-order Stokes SRS of the ring skeleton was produced, can be attributed to the vibration energy transfer between vibration energy levels of CC and CH. The Stokes and anti-Stokes SRS rings, which originated from the intramolecular energy-transfer-enhanced four-wave mixing (FWM) processes, can be observed only in the forward direction along different angles apart from the pump beam direction.