Improvement of the precision of coherent anti-Stokes rotational Raman scattering for oxygen and oxygen containing gas mixtures

燃烧纯氧代替空气作为氧化剂在工业过程中变得越来越重要，因为这有可能减少向大气中释放大量导致气候变化的二氧化碳。此外，缺乏氮气导致氮氧化物排放显著减少。进一步优化这些过程需要对全氧燃料燃烧过程有详细的了解和理解。因此，需要具有高时空分辨率的实验数据。基于非侵入性激光的测量技术，如CARS，非常适合此类测量问题。除了振动CARS外，旋转CARS由于可以直接用于多物种检测而越来越受到人们的关注。然而，为了进行数据评估，需要对旋转CARS光谱进行精确建模。这里仍然强烈需要未知的s分支拉曼线宽。这些数据适用于纯N2，但不适用于O2和燃烧相关气体混合物。该项目的主要目标是缩小这一差距。通过使用延时皮秒旋转CARS技术，可以测量纯O2和含O2的气体混合物的拉曼相干性衰减率。这些衰减率可以用来计算相应的s分支拉曼线宽。这些数据将有助于提高涉及O2过程的旋转CARS技术的精度。此外，这些正确的线宽信息可用于拟合CARS碰撞模型中的经验参数。

Combustion based on pure oxygen instead of air as an oxidizer is getting more and more important for industrial processes, since this is a possibility to reduce the release of large quantities of climate changing CO2 into the atmosphere. In addition the lack of N2 results in a significant reduction of the NOx emissions. A further optimization of such processes requires a detailed knowledge and understanding of the oxy-fuel combustion process. Therefore experimental data with high temporal and spatial resolution are required. Non-invasive laser based measurement techniques like e.g. CARS are very well qualified for such measurement problems. Beside vibrational CARS nowadays rotational CARS is getting more and more into focus, since it can directly be used for a multi species detection. Nevertheless for a data evaluation a precise modeling of the rotational CARS spectra is necessary. Here is still a strong need for unknown S-branch Raman linewidths. These data are available for pure N2 but not for O2 and combustion relevant gas mixtures.The main objective of this project is to close this gap. By using the time delayed picoseconds rotational CARS technique it is possible to measure the decay rate of the Raman coherence for pure O2 and gas mixtures with O2. These decay rates can be used to calculate the corresponding S-branch Raman linewidths. These data will then help to improve the precision of the rotational CARS Technique for processes involving O2. In addition these correct linewidth information can be used to fit the empirical parameters within the CARS collision models.