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Single-shot fs/ns rotational CARS for temporally and spectrally resolved gas-phase diagnostics
Proceedings of the Combustion Institute ( IF 5.3 ) Pub Date : 2020-10-10 , DOI: 10.1016/j.proci.2020.09.010
Ali Hosseinnia , Maria Ruchkina , Pengji Ding , Joakim Bood , Per-Erik Bengtsson

We report thermometry and new Raman linewidth data using a novel method for time-domain rotational coherent anti-Stokes Raman spectroscopy (RCARS) on single-shot basis. The coherences are generated by two fs pulses and probed by a ns pulse. The resulting signal is detected using a combined spectrograph/streak camera setup with high spectral and temporal resolution. Rotational CARS spectrograms of nitrogen (N2), ethylene (C2H4), ethane (C2H6), and argon (Ar) are demonstrated at ambient condition. Self-broadened N2–N2 S-branch Raman linewidths were measured on single-shot basis and show excellent agreement with literature values. Furthermore, Raman linewidths of N2 S-branch perturbed by C2H4 and C2H6 were measured for the first time. The time-resolved approach was also utilized to separate complex spectra from a mixture of species through their difference in coherence lifetimes. Since the Raman coherences decay much faster for both ethane and ethylene than for nitrogen, pure nitrogen spectra could be obtained by analyzing only the temporal tail of the signal. Moreover, a model for time-resolved RCARS of N2 was developed, which employs the single-shot measured Raman linewidths to calculate the corresponding spectro-temporally resolved spectrograms at different temperatures. The model was used to evaluate the temperature from single-shot data of an N2/C2H6 mixture, showing very high accuracy. The demonstrated method constitutes an essential improvement for single-shot thermometry as it does not require pre-knowledge about collider species concentrations and their impact on linewidths.



中文翻译:

单次fs / ns旋转CARS,用于时间和光谱解析的气相诊断

我们在单次使用时域旋转相干反斯托克斯拉曼光谱法(RCARS)的新颖方法报告温度和新的拉曼线宽数据。相干由两个fs脉冲产生,并由ns脉冲探测。使用具有高光谱和时间分辨率的组合光谱仪/条纹相机设置来检测结果信号。在环境条件下证明了氮气(N 2),乙烯(C 2 H 4),乙烷(C 2 H 6)和氩气(Ar)的旋转CARS谱图。自增宽N 2 –N 2S分支拉曼线宽是单次测量的,与文献数据显示出极好的一致性。此外,首次测量了被C 2 H 4和C 2 H 6扰动的N 2 S分支的拉曼线宽。通过它们的相干寿命差异,时间分辨方法还可以从物种混合物中分离出复杂的光谱。由于乙烷和乙烯的拉曼相干衰减远快于氮,因此仅通过分析信号的时间尾部即可获得纯氮谱。此外,N 2的时间分辨RCARS模型开发了使用单次测量的拉曼线宽来计算在不同温度下对应的由光谱暂时解析的谱图的方法。该模型用于从N 2 / C 2 H 6混合物的单次数据评估温度,显示出很高的准确性。所证明的方法构成了单次测温法的一项重要改进,因为它不需要预先了解对撞机物种的浓度及其对线宽的影响。

更新日期:2020-10-11
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