Rotation-Vibration(Rotation) Collision Relaxation In Gas Containing Excited State H₂

The vibration(rotation)collision relaxation of excited molecules plays an important role in atmospheric chemistry,hydrogen plasma nuclear fusion reactions,optical pumping dynamics,and laser-induced chemical reactions.The collision and relaxation process of vibration-rotation excited molecules in mixed gas systems plays a leading role in many non-equilibrium dynamic environments.As the simplest diatomic molecule,H2 molecule has a simple theoretical model and is easy to calculate the correlation rate coefficient.The experimental research on the energy transfer process of the rotation-vibration collision between the highly excited rotational state H2 molecules and the gas molecules can fill the gaps in the relevant experimental data and provide experimental data for the establishment of the rotation-vibration collision energy transfer mechanism and theoretical model.This article discusses the collision vibration-vibration rotation(V-VR)energy transfer process in the HBr(v"=5,6)-H2 mixed gas system and the collision rotation-vibration rotation(R-VR)in the H2(1,7)-N2 mixed gas system.The energy transfer process was studied.At room temperature(T=295K),the sample tube is filled with HBr-H2 mixed gas with a molar ratio of 0.4,and the total pressure is 500Pa.The YAG-pumped OPO laser is degenerate and super-Raman pumped to excite HBr to the X1?+ ground electronic state v"=5,6 vibration excited state.Through coherent anti-Stokes Raman light(CARS)spectroscopy and laser induced fluorescence(LIF)spectroscopy,the energy level population of H2 and HBr molecules after collision and their evolution over time are detected respectively.In addition,the collision relaxation process of HBr(v"=5,6)-H2 is also discussed.The CARS spectroscopy technique was used to detect the population distribution of each vibrational rotation energy level after the collision of H2 molecules.From the scanning CARS spectra of the 2-1 vibration band and the 3-2 vibration band of the H2 molecule,the different rotational states of the H2 molecule at the v=1 and 2 vibrational energy levels after colliding with HBr(v"=5,6)are determined populated.A simple dynamic model analysis and the relative intensity ratio of the scanning CARS spectrumgive the ratio of the population of the corresponding vibration-rotational energy levels.Then,from the Boltzmann distribution under the dynamic thermal equilibrium of the H2(v=0)fundamental vibration,the population density of the H2 molecules(v"=1,2)in each vibratory rotation state after the collision is calculated.Among them,when the ratio of population density has multiple values,the actual population density can be determined according to the scanning CARS signal profile analysis.The time-resolved LIF spectroscopy technique was used to detect the time evolution profile of the population on the vibrational energy level of HBr(v"?5,6)after the collision.The narrow linewidth laser provided by the Ti gem laser two-photon excitation collision HBr(v"?5,6)each vibration excited state to HBr(A1?v')state,and the detection A?X in the direction perpendicular to the laser beam The instantaneous time-resolved fluorescence intensity of the band.It can be seen from the profile of the fluorescence evolution over time that after excitation of the HBr(v"=5,6)vibrational state,the population of v"=3,4 energy levels increases rapidly,the population number at the v"=4,5 energy level increases slowly,which is direct evidence of the occurrence of the two-quantum near-resonance relaxation process in the HBr(v"=5,6)+H2 system.This paper also studies the collisional rotation-vibration rotation(R-VR)energy transfer process in the H2-N2 mixed gas system.The H2 molecule was excited by stimulated Raman to X1?+(v=1,J=7)high-position transition state,and CARS spectroscopy was used to detect the population of N2 molecules after collision.Scanning CARS spectra confirmed that N2 molecules have three peaks(2,11),(2,7),(2,4)at the v=2 energy level after colliding with H2(1,7);There are two peaks(3,14)and(3,8)at the energy level of v=3.Keep the total pressure of the mixed gas unchanged(500 Torr)and change the molar ratio of H2.The experimental results show that with the increase of the molar ratio of H2,the population energy level of the N2 molecule does not change after the collision,while the CARS spectrum there is a certain increase in peak intensity.With the increase of donor molecules,the collision transfer energy level of acceptor molecules does not change significantly,but the population of particles increases.