Study On The Effect Of Hydrogen Bonds On Stimulated Raman Scattering In Solution

Through the Raman spectrum we can be intuitive to get some of the specific peaks of the material,and through the specific peaks know the intrinsic vibrational model of the materials.When the substance is in the high temperature and high pressure environment,the material is excited under the intense laser.By measuring the stimulated Raman spectrum,we can understand the change of matter,such as the length of the keys and so on.In the process of interaction between substances,hydrogen bonds play a very important role.Although the hydrogen bond is a weak bond,its formation will have an important effect on the shape and structure of the material,and we can see these changes by measuring the Raman spectrum of the substance.In this paper,we used the knowledge of spontaneous Raman,stimulated Raman scattering,hydrogen bonds,laser induced breakdown and laser induced plasma,and analyzed the Raman spectra of mixed solution of water and hydrogen peroxide,mixed solution of benzene and bromobenzene.The influence of hydrogen bonds on the stimulated Raman scattering of two different mixed solutions was studied to understand the interaction and changes of the material.It is also possible to enhance the understanding of the stimulus process.?1?The forward stimulated Raman scattering spectra of the solution were measured by pulsed laser with the laser energy of 90 m J and wavelength of 532 nm in the mixed solution of benzene and bromobenzene.When the volume ratio of the solution is 1: 2,the Raman shift of the C-Br out-of-plane bending vibration mode is minimized due to the influence of the hydrogen bonds,and the peak intensity of the weakly excited vibration mode?3060 cm-1?compared with the ring breathing vibration mode?992 cm-1?,reaches to be the strongest one.The reason why the peak intensity becomes stronger is that in the mixed solution under the intense laser there apears plasma,such like?bromobenzene-benzene?+,?bromobenzene-bromobenzene?+ or?bromobenzene-benzene-bromine?+,isomeric dimer or trimer cations,and heterodimer or trimer cations,which increase the Raman scattering cross section of the CH stretching vibration.And when the volume ratio of the solution is 1:2,the most stable trimer?bromobenzene-benzene-bromobenzene?is formed.In the trimer,CH … Br hydrogen bonds can elongate the C-Br bond or reduce the force constant of the C-Br bond,leading to reduce the Raman shift of the C-Br out-of-plane bending vibration mode.In addition,the optimized structure of the trimer was simulated by Gaussian?EM64L-G09 Rev B.01?software.?2?When the laser energy is 40 m J,the wavelength of the pulse laser is 532 nm,the forward and backward stimulated Raman scattering spectra and spontaneous Raman spectra in the mixed solution of the water and hydrogen peroxide were measured.The Raman peaks of the free“OH”groups at 3060 cm-1 appearing in the backward stimulated Raman scattering spectra.The frequency of the free “OH” groups and the normal OH stretching vibration peaks at different mixing ratios shift.We believe that a small amount of free “OH” is produced in the solution.On the one hand,the dissociation of hydrogen peroxide can produce the free“OH”groups under the strong laser;on the other hand,the ionization of H₂O₂?H₂O?_1-n in the mixed solution results in the formation of the free“OH”groups.When at different concentrations,the H…OH hydrogen bonds between the clusters formed by water and hydrogen peroxide can attenuate the frequency of the vibrations,resulting in a certain frequency shift of the other oxygen hydrogen peaks.Under the intense laser,the material is excited and the laser induced plasma is generated,and the hydrogen bond between the molecules will have an effect on the vibration frequency of the molecule.The theory of plasma provides some theoretical support for the change of the stimulated Raman scattering spectrum,and the correlation knowledge about hydrogen bonds also provides a theoretical explanation for the change of the spectrum.The laser induced breakdown effect can not only be used to analyze the changes of the liquid properties of various substances under high temperature and high pressure,but also can study the solid,gaseous and other materials.So there is a relatively large practical significance.