Study Of Broadband Stimulated Raman Scattering Of Acetone Binary Solution

Stimulated Raman scattering（SRS）is a coherent and non-linear form of Raman scattering that has spectral Raman scattering properties while magnifying the optical signal up to several orders of magnitude.The phenomenon of excited Raman scattering occurs widely in gaseous,liquid and solid media.Liquids are of great interest to researchers because of their high damage tolerance threshold,low price and easy preservation.Acetone is a highly Raman active liquid with a large cross section for Raman scattering and is also known as a universal solvent that can be mixed with most organic solutions.Carbon disulfide has a slow vibrational relaxation time and can withstand high incident pumping intensities.Carbon tetrachloride is an organic compound with a low Raman threshold.Both liquids are effective in producing stimulated Raman spectra and by mixing acetone with carbon disulfide and carbon tetrachloride solutions respectively,we can better understand the special phenomena that may exist from the interaction between both molecules.The following innovative results have been achieved in this thesis:1.A pulsed Nd:YAG laser at 532 nm was used as the excitation source to pump SRS from a mixed acetone-carbon disulfide solution.Two significantly asymmetric excited Raman broadening spectra were obtained at the first-order Stokes peak of carbon disulfide and at the first-order Stokes peak of acetone,respectively.The maximum band widths of 785 cm^-1and 1005 cm^-1were achieved at a volume ratio of7:3 for both liquids.Simultaneous theoretical simulations using density flooding theory（DFT）reveal that the double broad band is caused by the weak hydrogen bonding of C-H…S and the resonant coupling of adjacent vibrational modes.The results are of some reference value for studying the generation of continuum radiation by liquid media.2.The SRS properties of acetone-carbon tetrachloride mixture were investigated using a 532 nm pulsed Nd:YAG laser as the pumping source.When acetone and carbon tetrachloride are mixed in different volume ratios,with a volume ratio of 3:7between the two influenced by resonant resonance interactions,the weak C-H antisymmetric stretching vibration mode of acetone is enhanced,while the higher-order Stokes peak of carbon tetrachloride is also excited.Combined with density flooding theory,it is revealed that the intermolecular vibrational coupling effect of mixed liquids and the generation of laser-induced plasma greatly increase the scattering cross section of acetone C-H stretching vibrations,thus enhancing the excited Raman scattering of mixed liquids.The results of this study provide a new approach to understand the mechanism of intermolecular interactions of mixed liquids.