Comprehensive CO detection in flames using femtosecond two-photon laser-induced fluorescence.
Comprehensive CO detection in flames using femtosecond two-photon laser-induced fluorescence.
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DOI：
10.1364/oe.25.025809
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发表时间：
2017-10
期刊：
影响因子：
3.8
通讯作者：
Bo Li;Xiaofeng Li;Dayuan Zhang;Q. Gao;M. Yao;Zhongshan Li
中科院分区：
文献类型：
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作者：
Bo Li;Xiaofeng Li;Dayuan Zhang;Q. Gao;M. Yao;Zhongshan Li
我们展示了一种飞秒双光子激光诱导荧光（fs-TPLIF）技术，用于灵敏的CO检测，使用9 μJ和45 fs的230 nm脉冲。分析了fs-TPLIF在激发分子种类方面的优势。光谱的CO fs-TPLIF记录在稳定的层流火焰空间分辨整个火焰前锋。在燃烧区观察到B→A跃迁的（0，n）和（1，n）热带，这归因于fs激发的宽带性质。跨激发光束的焦点记录的CO fs-TPLIF信号示出了相对平坦的强度分布，尽管激光强度变化陡峭，这与纳秒和皮秒TPLIF相比对于CO成像是有益的。这种现象可以通过光电离来解释，光电离在短脉冲持续时间内由于高峰功率而主导激发B态的布居耗尽，但是由于低脉冲能量而仅贡献总计可忽略的X态耗尽。甲烷/空气火焰中的单次CO fs-TPLIF图像记录通过成像的宽带荧光。结果表明，fs-TPLIF是一个很有前途的工具，在火焰中的CO成像。
We demonstrate a femtosecond two-photon laser-induced fluorescence (fs-TPLIF) technique for sensitive CO detection, using a 230 nm pulse of 9 µJ and 45 fs. The advantages of fs-TPLIF in excitation of molecular species were analyzed. Spectra of CO fs-TPLIF were recorded in stable laminar flames spatially resolved across the flame front. A hot band (1, n) together with the conventional band (0, n) of the B→A transitions were observed in the burned zone and attributed to the broadband nature of the fs excitation. The CO fs-TPLIF signal recorded across the focal point of the excitation beam shows a relatively flat intensity distribution despite of the steep laser intensity variation, which is beneficial for CO imaging in contrast to nanosecond and picosecond TPLIF. This phenomenon can be explained by photoionization, which over the short pulse duration dominates the population depletion of the excited B state due to the high peak power, but only contributes in total a negligible X state depletion due to the low pulse energy. Single-shot CO fs-TPLIF images in methane/air flames were recorded by imaging the broadband fluorescence. The results indicate that fs-TPLIF is a promising tool for CO imaging in flames.