CO<sub>2</sub>与高振动激发K<sub>2</sub>碰撞中的全分辨转动态分布

doi:10.3964/j.issn.1000-0593(2017)12-3658-06

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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 T_a=(523±60) K and a high energy distribution with T_b=(1 890±210) K. The proximity of T_a 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 T_a=(620±65) K and T_b=(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%.

Key words： Collisional energy transfer Stimulated emission pumping Transient fluorescence measurement Appearance and depletion profiles Highly vibrationally excited K₂ CO₂

Received: 2017-02-17 Accepted: 2017-05-22

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O561.5

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http://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2017)12-3658-06 OR http://www.gpxygpfx.com/EN/Y2017/V37/I12/3658