Study Of Stimulate Raman Scattering Of Water And Deuterated Water Molecules

Water(H2O)is important component of living organisms.The oxygen atom in another water molecule will interact intermolecularly when it approaches the hydrogen atom in this water thus forming a hydrogen bond(HB),it is the ever-changing HB that leads to the very complex nature of water.Hydrogen peroxide(H2O2)is a common class of oxidizing agents that can be used in H2 O and most organic solvents under relatively mild conditions.Heavy water(D2O)is often used as a stable isotopic reagent for H2 O to determine the internal structure and molecular composition of H2 O.Laser-induced breakdown(LIB)and stimulated Raman scattering(SRS)techniques were used to study H2O2 aqueous solution and ternary solutions of H2 O,H2O2 and D2 O.The following results were obtained in this thesis.(1)The Cascaded SRS of H2O2 aqueous solutions was investigated using a pulsed Nd: YAG laser with a wavelength of 532 nm.The transfer of excess electrons between H2O2 and H2 O molecules enhanced the SRS.Together,the decomposition of H2O2 and the intense SRS Stokes led to the generation of the crossing-pump effect of mixed solutions and the new Raman peak appears at wave number 4229 cm-1.When the energy is weak,the peak is generated by the O-H vibration of H2 O as the pump source to excite the O-O vibration of H2O2,when the energy is high,the peak is generated by the O-O vibration of H2O2 as the pump source to excite the O-H vibration of H2 O.Crossing-pump not only reduced the threshold but also generated the broadband coherent Raman comb,defined as a coherent radiation wavelength ranging from 434 to 837 nm(i.e.,a Raman shift ranging from-4225 to 6853 cm-1),the appearance of anti-Stokes SRS was attributed to the four-wave mixing(FWM).This research has a wide range of practical applications,ranging from optical coherent Raman comb generations to applications in medical laser combs and detection of spectra in mixed solutions.(2)The HB structure of the ternary mixture of H2 O,H2O2 and D2 O was investigated using spontaneous Raman and SRS spectroscopy.Under LIB effect,the presence of H2O2 makes it easier to generate plasma and excess electrons,which will enhance HB structure in H2 O.Meantime,the tetrahedral structures of H2 O and D2 O were destroyed in the process of isotopic substitution,which weakened inter-molecular vibration coupling and promoted the transition to the non-tetrahedral HB structure.The changes in Raman shifts of O-H and O-D vibrations are observed on the Raman spectra.This study provides a more reliable basis for isotope substitution studies and more information for subsequent studies on the vibration of O-H and O-D.