Vibration-rotation Collision Energy Transfer Of Excited State Hbr Molecules And Gas Molecules

The collision energy transfer process between atoms,molecules and ground state molecules in the excited state is a hot topic in the field of atomic and molecular collision studies.It is a common method for studying the changing process between various vibrational state molecules.The HBr molecules is excited by degenerate super Raman pumping and the collision energy transfer process between the vibrational excited HBr molecules and H₂?CO₂ molecules.We hope to be able to provide some basic data for the study of high vibrational dynamics and further expand measurement and analysis methods for the collision of excited molecules.The stimulated Raman pump was used to excite HBr to the?1,12?excited state,the vibration-rotation and translation?V-RT?energy transfer between the excited HBr molecules and CO₂ molecules was studied.The excitation of the HBr molecule was determined by the CARS spectrum and the relative intensity of CARS spectra was measured,the population densities of the?1,12?and?0,15?levels of HBr molecules are obtained to be n₁=0.54×10¹³cm^-3and n₂=1.1×10¹³cm^-3,respectively.Combining the laser-induced fluorescence?LIF?intensity ratios of CO₂ before and after the collision,the sum of the appearance rate coefficients for all the rotational states in the CO₂?00⁰0,J??V-RT?energy transfer is?1.3±0.3?×10^-1010 cm³ molecule^-1s^-11 and the average depletion rate coefficient for the low rotational states is?2.9±0.8?×10^-10cm³molecule^-1s^-1.The results show that the total appearance rate coefficient is smaller than the average depletion rate coefficient in the V-RT energy transfer,but they are consistent on the order of magnitude.According to the rotational states distribution of CO₂?00⁰0,J?molecules after the collision of HBr and CO₂?00⁰0?,it can be seen that about 65%of the CO₂?00⁰0,J?molecules are in the low J state and about35%of the CO₂?00⁰0,J?molecules are in the high-J state.The low energy distribution is a weak collision and has relatively low translational energy.The high-energy distribution is a nonelastic strong collision with a large translational energy.For CO₂J=60-74 high rotation states,some of the translational temperatures exceed the sample cell temperature 300K.With the increase of J value,the average change for the translational temperature and translational energy of the center of mass increase.We have excited the HBr molecules to the v??=5 and 6 vibrational excited states using the degenerate stimulated super Raman pump and studied the collision energy transfer process between the vibrational excited HBr molecules and H₂ molecules.From the scanning CARS spectrum of the H₂ molecule,we can see that the vibrational states v=1 and 2 of the H₂ molecules are populated.From the peak intensity of the CARS spectrum,it can be seen that the intensity at the v=1 energy level is greater than the intensity at the v=2 energy level,from which it can be determined that two quantum near resonance processes HBr?v??=5?6?+H₂?0??HBr?v??=3?4?+H₂?1?occur.The ratio of population density?can be determined by comparison of the curve of the time-resolved CARS spectrum fitted to the experimental curve,the occurrence of two quantum near resonance processes HBr?v??=5?6?+H₂?0??HBr?v??=3?4?+H₂?1?is further verified.Combining the ratio of the population density and the peak intensity of the CARS spectrum,the H₂population densities for each rotational energy levels of v=1 and v=2 after H₂ collision were determined.