The Fermi resonance behaviours of the two groups of binary solutions -- pyridine and methanol, benzene and carbon tetrachloride, under different pressures are investigated according to their Raman spectra. The effect of pressure on Fermi resonance in binary solution differs significantly from that in pure liquid. In a binary solution, with the intermolecular distance shortening, the intermolecular interaction potential increases, the shift rates of the Raman spectral lines increase, the spectral line splitting occurs ahead of that in pure liquid, and the wavenumber separation A0 between the unperturbed harmonic levels shifts more quickly, too. The Fermi resonance parameters, the coupling coefficient W and the intensity ratio R of the two Raman bands, decrease rapidly with pressure increasing, and the pressure at which Fermi resonance phenomenon disappears is much lower than that in pure liquid, especially in the solution whose molecules are of the same polarity. This article is valuable in the identification and the assignment of spectral lines under high pressure, as well as the study of high pressure effect, intermolecular interaction, and solvent effects in different cases, etc.
We have measured the Raman spectra and UV-Vis absorption spectra of linear polyene biomolecules(β-carotene and lycopene) in CS2 at low concentrations(10-6-10-10 mol/L).With decreasing concentration,all the carbon-carbon vibrations form a coherent mode in ordered β-carotene and lycopene due to extended π-conjugation that gives strong electron-phonon coupling,which leads to an anomalous experimental phenomenon.We observed an extremely high Raman scattering cross section(RSCS) and the Raman activities in β-carotene and lycopene are characterized by intensive overtones and combinations.Further,the UV-Vis absorption bands become narrower.
OUYANG ShunLi1,2,SUN ChengLin1,2,ZHOU Mi1,2,LI DongFei2,WANG WeiWei1,2,QU GuanNan1,LI ZuoWei1,2,GAO ShuQin1 & YANG JianGe3 1 State Key Laboratory of Superhard Materials,Jilin University,Changchun 130012,China
This paper reports that vibrational spectroscopic analysis on hYdrogen-bonding between acetone and water comprises both experimental Raman spectra and ab initio calculations on structures of various acetone/water complexes with changing water concentrations. The optimised geometries and wavenumbers of the neat acetone molecule and its complexes are calculated by using ab initio method at the MP2 level with 6-311＋G（d,p） basis set. Changes in wavenumber position and linewidth （fullwidth at half maximum） have been explained for neat as well as binary mixtures with different mole fractions of the reference system, acetone, in terms of intermolecular hydrogen bonding. The combination of experimental Raman data with ab initio calculation leads to a better knowledge of the concentration dependent changes in the spectral features in terms of hydrogen bonding.
In this study, our vibrational spectroscopic analysis is made on hydrogen-bonding between dimethyl sulfoxide and water comprises both experimental Raman spectra and ab initio calculations on structures of various dimethyl sulfoxide/water clusters with increasing water content. The Raman peak position of the v（S=O） stretching mode of dimethyl sulfoxide serves as a probe for monitoring the degree of hydrogen-bonding between dimethyl sulfoxide and water. In addition, the two vibrational modes, namely, the CH3 symmetric stretching mode and the CH3 asymmetric stretching mode have been analysed under different concentrations. We relate the computational results to the experimental vibrational wavenumber trends that are observed in our concentration-dependent Raman study. The combination of experimental Raman data with ab initio calculation leads to a better knowledge of the nature of the hydrogen bonding and the structures of the hydrogen-bonded complexes studied.
We measured the resonant Raman spectra of all-trans-β-carotene in solvents with different densities and concentrations at different temperatures. The results demonstrated that the Raman scattering cross section （RSCS） of short-chain polymer all-trans-β-carotene is extremely high in liquid. Resonance and strong coherent weakly damped CC bond vibrating properties play important roles under these conditions. Coherent weakly damped CC bond vibration strength is associated with molecular ordered structure. All-trans-β-carotene has highly ordered structure and strong coherent weakly damped CC bond vibrating properties, which lead to large RSCS in the solvent with large density and low concentration at low temperature.
We demonstrate stimulated supercontinuum-radiation of carbon disulfide （CS2） influenced by biological molecules all-trans-stimulated Raman scattering, stimulated Brillouin scattering, all-trans-β-carotene, liquid core optical fibre-carotene in liquid core optical fibre （LCOF）. By virtue of the broad fluorescence characteristics and large third-order optical nonlinearities of all-trans-β-carotene, the high-order Stokes lines of stimulated Raman scattering （SRS） and the multi-order Stokes lines of stimulated Brillouin scattering （SBS） excitated by SRS are observed at low input-laser energies. The results indicate that the fluorescence not only enhances the SRS, but also the SBS. These Stokes lines generate the SRS-SBS supercontinuum radiation （RBSR）. A flat-amplitude bandwidth of 110 nm from 515 nm to 625 nm is observed when a frequency-doubled Nd：YAG laser at 532 nm with an energy of 0.86 mJ is used. This result is expected to be useful for the multi-wavelength fibre laser.
