Abstract：The full state-resolved distribution of scattered CO2(0000) molecules from collisions with highly vibrationally excited Na2(ν″=30 and 45) is reported and investigated how internal energy content impacts the dynamics for collisional quenching of high energy molecules. Stimulated emission pumping was used to excite the Na2(ν″=30, J=11) and Na2(ν″=45, J=11). Under single-collision conditions, rotational levels of the vibrationally relaxed Na2(ν″-1) and Na2(ν″-2) are identified. Levels attributable to upward vibrational transfer could not be observed. The change in Na2 rotational energy was determined. Quantifying the simultaneous population change for low J states is accomplished by transient line profile measurements for individual states. The line width is a measure of the translational energy spread of the scattered molecules and the area under the line profile is a measure of the J-specific population. The nascent translational temperature Tpres (for presence) and Tdep (for depletion) are determined from the measured line widths Δνpres and Δνdep, respectively. The presence line widths Δνpres were obtained by fitting the double-Gaussian function to the transient line profile data at t=1 μs. The lab-frame translational temperature Tpres for the presence of scattered CO2 molecules and the relative (center-of-mass frame) translational temperatures Trel for Na2(ν″) /CO2 collisions were determined based on Δνpres measurements. Average translational energy gains for the presence of CO2(0000, J) following collisions with vibrationally excited Na2 are determined using 〈Erel〉=3/2k(Trel-Tcell). The comparison shows that the Na2 vibrational energy that goes into the translational energy of the CO2 strongly depends on the initial energy: the translational energy of the J-specific collision pruducts increases by 56% or more for a 35% increase in donor vibrational energy. The appearance rate constants for individual CO2 rotational states are determined. The total appearance rate constant for Na2(ν″=30) is kapp=(6.6±1.5)×10-10 cm3·molecule-1·s-1. This result is comparable to that for Na2(ν″=45), where the appearance rate constant is kapp=(5.9±1.3)×10-10 cm3·molecule-1·s-1. The results show that the Na2(ν″)/CO2 collision frequency is not particularly sensitive to the amount of Na2(ν″) vibrational energy. The full energy transfer distributions P(ΔE) for product energy gain confirm that the ΔE distributions broaden rapidly for relatively small increases in donor energy for Na2(ν″)/CO2 collisions. P(ΔE) curves for Na2(ν″=30) are shifted to lower ΔE values compared to Na2(ν″=45) data. The ΔE values in P(ΔE) include the change in CO2 rotational energy and the change in translational energy of Na2(ν″) and CO2 plus the change in rotational energy of Na2(ν″). Numerical integration of P(ΔE) over the full range of ΔE yields 〈ΔE〉trans=590 cm-1; in comparison, 〈ΔE〉trans=880 cm-1 for Na2(ν″=45).
Key words：Collisional energy transfer; Laser induced fluorescence; Transient line profile; Rate contant; Energy gain distribution function; High vibrationally excited Na2; CO2
王淑英，尤德昌，马文佳，杨若凡，张仰志，於子雷，赵小芳，沈异凡. Na2高振动态与CO2间碰撞转移概率分布的实验测量[J]. 光谱学与光谱分析, 2023, 43(06): 1760-1764.
WANG Shu-ying, YOU De-chang, MA Wen-jia, YANG Ruo-fan, ZHANG Yang-zhi, YU Zi-lei, ZHAO Xiao-fang, SHEN Yi-fan. Experimental Collisional Energy Transfer Distributions for Collisions of CO2 With Highly Vibrationally Excited Na2. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2023, 43(06): 1760-1764.
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