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首页> 外文期刊>Journal of Physics, D. Applied Physics: A Europhysics Journal >Picosecond CARS measurements of nitrogen vibrational loading and rotational/translational temperature in non-equilibrium discharges
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Picosecond CARS measurements of nitrogen vibrational loading and rotational/translational temperature in non-equilibrium discharges

机译：皮秒汽车在非平衡放电中氮振动负荷和旋转/平移温度的测量

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Picosecond coherent anti-Stokes Raman spectroscopy (CARS) is used to study vibrational energy loading and relaxation kinetics in nitrogen and air ns pulsed non-equilibrium plasmas, in both plane-to-plane and pin-to-pin geometries. In 10 kHz repetitively pulsed plane-to-plane plasmas, up to ～50% of coupled discharge power is found to load vibrations, in good agreement with a master equation kinetic model. In the pin-to-pin geometry, ～40% of total discharge energy in a single pulse in air at 100 Torr is found to couple directly to nitrogen vibrations by electron impact, also in good agreement with model predictions. Post-discharge, the total quanta in vibrational levels v = 0-9 is found to increase by ～60% in air and by a factor of ～3 in nitrogen, respectively, a result in direct contrast to modelling results which predict the total number of quanta to be essentially constant until ultimately decaying by V-T relaxation and mass diffusion. More detailed comparison between experiment and model show that the vibrational distribution function (VDF) predicted by the model during, and directly after, the discharge pulse is in good agreement with that determined experimentally. However, for time delays exceeding ～1 μs, the experimental VDF shows populations of vibrational levels v 2 greatly exceeding modelling results, which predict their predominant decay due to net downward V-V transfer and corresponding increase in v = 1 population. This is at variance with the experimental results, which show a significant monotonic increase in the populations of levels v = 2-9 at t ～ 1-10 μs after the discharge pulse, both in nitrogen and air, before gradually switching to relaxation at t ～ 10-100 μs. It is concluded that a collisional process is likely feeding high vibrational levels at a rate which is comparable to the rate at which population of the high levels is lost due to net downward V-V energy transfer. A likely candidate for the source of additional vibrational quanta is quenching of metastable electronic states of nitrogen to highly excited vibrational levels of the ground electronic state. The effect of electronic-vibrational (E-V) coupling on time-resolved N_2 vibrational populations and temperature, estimated using a phenomenological E-V energy transfer model, provides qualitative interpretation of the present experimental results.
机译：皮秒相干反斯托克斯拉曼光谱（CARS）用于研究平面和平面几何以及针对针几何中氮气和空气ns脉冲非平衡等离子体中的振动能量加载和弛豫动力学。在10 kHz重复脉冲的平面间等离子体中，发现高达〜50％的耦合放电功率可负载振动，这与主方程动力学模型十分吻合。在销钉到销钉的几何形状中，发现在100 Torr的空气中，单个脉冲中约40％的总放电能量与电子撞击直接耦合到氮振动，也与模型预测非常吻合。放电后，发现振动水平v = 0-9的总量子在空气中分别增加了〜60％，在氮气中增加了〜3倍，这与预测总数的建模结果直接相反。量子常数基本上是恒定的，直到通过VT弛豫和质量扩散最终衰减为止。实验与模型之间更详细的比较表明，模型在放电脉冲期间以及放电脉冲之后直接预测的振动分布函数（VDF）与实验确定的振动分布函数非常吻合。但是，对于超过〜1μs的时间延迟，实验VDF显示振动水平v 2的数量大大超过了建模结果，这预示了由于净向下V-V传递和v = 1数量的相应增加而导致的主要衰减。这与实验结果不一致，实验结果表明，在氮气和空气中，在放电脉冲后，t〜1-10μs时，v = 2-9的能级群体显着单调增加，然后逐渐转变为t的弛豫〜10-100μs。结论是，碰撞过程可能以与由于净向下V-V能量转移而损失高能级的速率相当的速率提供高能级。额外的振动量子源的可能候选者是将亚稳态的氮电子态淬灭到基态电子态的高激发振动能级。电子振动（E-V）耦合对时间分辨的N_2振动人口和温度的影响，使用现象学的E-V能量转移模型估算，可以对本实验结果进行定性解释。

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