Ro-vibrational distribution measurement in transient discharges by coherent anti-Stokes Raman scattering (A02)

振动（和旋转）激发分子在等离子体化学中起着关键作用，因为它们具有高内能，强烈地影响化学过程。一个悬而未决的问题是激发态在催化反应中的作用。分子的激发是通过与等离子体中存在的高能电子的碰撞和已经被激发的分子的激发转移而发生的。详细的物理机制和速率常数往往不为人所知或尚未在实验中得到验证。此外，模拟通常非常复杂，特别是与大气压下的高瞬态放电有关，其中时间尺度从电子相互作用的ps延伸到碰撞转移和化学反应的μs甚至ms。因此，本项目旨在利用相干反斯托克斯拉曼散射（CARS）测量CO2和N2的反振动激发。除了实验装置之外，还开发了一种新的分析程序，允许处理非平衡分布函数。此外，分析模型允许利用A1项目的电场数据和电流测量值从头开始预测种群分布。证明了等离子体密度和电场在放电过程中的独立控制。这使得等离子体体中几乎所有电子能量的优化耦合进入振动激发。

Vibrational (and rotational) excited molecules play a key role in plasma chemistry since due to their high internal energy they strongly affect the chemical processes. An open question is the role of excited states in catalytic reactions. The excitation of the molecules occurs by collisions with energetic electrons present in the plasma and by excitation transfer from already excited molecules. The detailed physical mechanisms and rate constants are often not known or have not been validated in experiments. Further, simulations are generally very involving, in particular in connection with highly transient discharges at atmospheric pressures, where time scales stretch from ps for the electron interaction to μs or even ms for collision transfer and chemical reactions. Therefore, this project aims at the measurement of the ro-vibrational excitation of CO2 and N2 by coherent anti-Stokes Raman scattering (CARS). In addition to the experimental setup also a new analysis procedure has been developed that allows addressing non-equilibrium distribution functions. Further, an analytical model allows ab-initio prediction of the population distributions with electric field data and current measurements taken from project A1. Independent control on plasma density and electric field in ns-discharges is demonstrated. This allows an optimized coupling of almost the entire energy of the electrons in the plasma bulk into vibrational excitation.