光谱学与光谱分析, 2017, 37 (12): 3658, 网络出版: 2018-01-04  

CO2与高振动激发K2碰撞中的全分辨转动态分布

Full State-Resolved Rotational Distribution of CO2 in Collisions with Highly Vibrationally Excited K2
作者单位
新疆大学物理科学与技术学院, 新疆 乌鲁木齐 830046
摘要
在K2+CO2中, 受激发射泵浦得到K2(E=3 500和4 000 cm-1)高位振动态, 研究了高振动激发K2与CO2碰撞产生的CO2全分辨转动态分布。 利用高分辨瞬时激光诱导荧光(LIF)测量了CO2(0000)J=2~74的转动和平移能量轮廓, 利用双高斯函数拟合, 分别确定各转动态的产生和倒空线宽, 从而得到碰撞产生的Doppler展宽、 平移温度和平移能。 对于K2不同的激发能E, 能量转移的机制是相似的, 为振动-转动/平移弛豫机制。 但碰撞出现部分的平移温度均超出池温, 而碰撞倒空部分的平移温度均略低于池温, 平移能随E的增加而增大, E增加14%, 平移能增加40%。 CO2(0000)转动态分布的半对数描绘给出了双指数分布, 对于K2 E=3 500 cm-1, 低J态分布Ta=(523±60) K, 高J态分布Tb=(1 890±210) K。 Ta接近池温, 说明低J态为近弹性碰撞, 属单量子弛豫过程, 而高J态为非弹性碰撞, 属多量子驰豫过程。 对于K2 E=4 000 cm-1同样有双指数行为, 低J分布Ta=(620±65) K, 高J分布Tb=(2 240±250) K。 高振动态K2(E)与CO2碰撞, E=4 000 cm-1比E=3 500 cm-1的Ta和Tb均约高19%, 说明转动分布对于K2不同能量是敏感的, 但弹性和非弹性分支比是基本相同的, 弱碰撞约占82%, 强碰撞约占18%。
Abstract
Highly vibrationally excited K2(E=3 500 and 4 000 cm-1) was achieved by stimulated emission pumping. The full state-resolved distribution of scattered CO2(0000) molecules from collisions with excited K2(E) was reported. The donor energy dependence for full J-state distribution of energy upstate in collisions has been investigated. Nascent rotational and translational energy profiles for scattered CO2(0000) molecules with J=2~74 were measured using high resolution transient laser induced fluorescence (LIF). The appearance line widths were obtained by fitting the double Gaussian function to the transient line profile data at t=1 μs. Doppler-broadened line widths and the relative (center of mass frame) translational temperatures for appearance and depletion of scattered CO2 molecules, the lab-frame translational temperatures and average translation energy of appearance section for K2(E)/CO2 collisions were determined. The energy transfer mechanism was similar at both donor energies, which was vibration-rotation/translation relaxation mechanism. But collisonal appearance temperatures were beyond the pool temperature, while collisonal depletion temperatures were slightly lower than the pool temperature, and the magnitude of energy transferred into translational energy increased with donor energy. The donor vibrational energy going into translational energy of the collision products was strongly dependent on the initial energy. The translational energy of the J-specific collision products increased by 40% or more for a 14% increase in donor vibrational energy. The nascent rotational distribution of scattered CO2(0000) molecules was shown for collisions with K2(E=3 500 cm-1). The semilog plot showed evidence of a biexponential distribution. A better description of the nascent rotational distribution came from fitting with the sum of two independent distributions. The fitting yielded a low-energy distribution with Ta=(523±60) K and a high energy distribution with Tb=(1 890±210) K. The proximity of Ta to the initial 553 K distribution showed that nearly elastic collisions populated the low J final states, which belong to single quantum relaxation processes. In contrast, the strong collisions that were responsible for the high energy tail were inelastic and involved large increases in J, which belonged to multi-quantum relaxation processes. The full J-state rotational distribution of CO2 from collisions with K2(E=4 000 cm-1) also showed biexponential behavior. Biexponential fitted results in Ta=(620±65) K and Tb=(2 240±250) K. Each of these values at E=3 500 cm-1 was approximately 19% greater than for corresponding values at E=3 500 cm-1. Thus, the highly energy donor molecules imparted more rotational energy for the full range of bath rotational states. The spread of the rotational distribution was sensitive to K2 difference energy, but the branching ratio for elastic and inelastic collisionswas the same The weak collision pathway accounted for ~82% of collisions with CO2(0000) products, while the strong collision pathway accounted for ~18%.

王淑英, 戴康, 沈异凡. CO2与高振动激发K2碰撞中的全分辨转动态分布[J]. 光谱学与光谱分析, 2017, 37(12): 3658. WANG Shu-ying, DAI Kang, SHEN Yi-fan. Full State-Resolved Rotational Distribution of CO2 in Collisions with Highly Vibrationally Excited K2[J]. Spectroscopy and Spectral Analysis, 2017, 37(12): 3658.

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