关键词: coherent anti-Stokes Raman scattering, particle population density, multiple quantum relaxation, effective lifetime

Abstract: The H$_{2}$ was excited to the H$_{2}$ X$^{1}\Sigma ^+_{\rm g}$ ($v=1$, $J=7$) energy level by the stimulated Raman pumping (SRP) technique, and the process of energy redistribution between H$_{2}(1,7)$ molecule and LiH was studied. The particle population density of H$_{2}(1,7)$ energy level is obtained by the coherent anti-Stokes Raman scattering (CARS) technique. The particle population density of each rotational level of H$_{2}$ ($v=1$, $J=7$, 5, 3) is analyzed with temperature after the collision between H$_{2}(1,7)$ molecule and LiH. It is found that the particle population density of each level increases with the increase in temperature after the collision. The time-resolved CARS spectra of each rotational energy level of H$_{2}$ ($v=1$, $J=7$, 5, 3) are analyzed at different temperatures. It is found that a multi-quantum relaxation process with $\Delta J=4$ occurs in H$_{2}(1,7)$ molecule, and the temperature accelerates the relaxation process. The effective lifetime of H$_{2}(1,7)$ energy level is obtained by plotting the semi-logarithmic plots of the CARS signal intensity and delay time of the level, and observing the law of the effective lifetime change with the temperature. It is found that the effective lifetime of H$_{2}(1,7)$ energy level shows an obvious decreasing trend with the increase of temperature.

Key words: coherent anti-Stokes Raman scattering, particle population density, multiple quantum relaxation, effective lifetime