Laser-induced breakdown spectroscopy (LIBS) is a technique for fast elemental determination, in which elemental information can be deduced by analyzing light emission from laser plasma. LIBS assisted with laser-induced fluorescence is a developing approach for modifying LIBS. Atoms of a target element in laser plasma are resonantly excited by a wavelength-tunable laser beam to realize signal enhancement with high selectivity and efficiency. Because excitation source is laser beams and observation source is UV-VIS-NIR optical signal, this technique can realize remote, fast, and real time detection, which has great potential in industrial fields. However, the spectral lines for excitation and observation are generally below 200 nm (vacuum ultraviolet), where laser and plasma emission are absorbed by air. Therefore, it is impossible to operate in open air, which seriously limits its further development in industrial fields.

Aiming to solve the specific problem of carbon fast determination in steel manufacture, Professor Xiangyou Li and PhD student Jiaming Li proposed to resonantly excite CN radicals in laser plasma to indirectly detect carbon signal. In the laser-ablation-breakdown process, carbon in materials and nitrogen in air are atomized simultaneously and combine to CN radicals. In B2Σ+-X2Σ+ system of CN radicals, (1, 0) and (0, 0) electronic-vibrational transitions are used for excitation and observation, respectively. The excitation and observation windows for CN radical fluorescence re both in the visible range, where operation in open air is feasible, and efficiency of optical systems and detectors are satisfactory. This work shows feasibility and potential to realize carbon fast determination and real-time information feedback in steel manufacture.

This work is funded by National Instrumentation Program of China (Grant No. 2011YQ160017) and National Natural Science Foundation of China (Grant No. 61575073). It has been published on Analytical Chemistry, 2017, 89(15): 8134-8139 (IF: 6.320) with the title of “Determination of carbon content in steels using laser-induced breakdown spectroscopy assisted with laser-induced radical fluorescence”.


Enclose:Jiaming Li, Zhihao Zhu, Rran Zhou, Nan Zhao, Rongxing Yi, Xinyan Yang, Xiangyou Li*, Lianbo Guo, Xiaoyan Zeng, and Yongfeng Lu, "Determination of carbon content in steels using laser-induced breakdown spectroscopy assisted with laser-induced radical fluorescence," Analytical Chemistry 89 (15), 8134-8139 (2017)

Figure  Process of laser-induced CN radical fluorescence in laser plasmas