Enhancement of Laser-Induced Breakdown Spectroscopy (LIBS) Detection Limit Using a Low-Pressure and Short-Pulse Laser-Induced Plasma Process
Enhancement of Laser-Induced Breakdown Spectroscopy (LIBS) Detection Limit Using a Low-Pressure and Short-Pulse Laser-Induced Plasma Process
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DOI：
10.1366/13-07131
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发表时间：
2013-11
影响因子：
3.5
通讯作者：
Zhen zhen Wang;Y. Deguchi;M. Kuwahara;Junjie Yan;Ji Ping Liu
中科院分区：
文献类型：
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作者：
Zhen zhen Wang;Y. Deguchi;M. Kuwahara;Junjie Yan;Ji Ping Liu
激光诱导击穿光谱（LIBS）技术具有响应速度快、灵敏度高、实时性好、非接触等特点，是一种非常有吸引力的元素分析技术。LIBS的挑战性目标之一是提高检测限。在本研究中，气相LIBS分析的检测限已提高通过控制压力和激光脉冲宽度。为了验证该方法，用纳秒和皮秒激光诱导低压气体等离子体。方法已用于汞的测定。分析Hg原子与NO的发射强度比（IHg/ INO）以评估LIBS的检测限，因为NO发射（干扰信号）是在空气中的N2和O2的等离子体产生和冷却过程中形成的。结果表明，当压强降低到几千帕时，IHg/INO的增强作用增强，在较低的缓冲气体压强下，皮秒击穿的IHg/INO总是远高于纳秒击穿的IHg/INO.在700 Pa下，采用脉宽为35 ps的皮秒激光，IHg/INO的增强作用提高了10倍以上。检测限提高到0.03 ppm（百万分之一）。我们还发现等离子体中心和边缘部分的光谱表现出不同的特征。在皮秒激光击穿过程中，边缘谱的IHg/INO比中心谱的IHg/INO高。
Laser-induced breakdown spectroscopy (LIBS) technology is an appealing technique compared with many other types of elemental analysis because of the fast response, high sensitivity, real-time, and noncontact features. One of the challenging targets of LIBS is the enhancement of the detection limit. In this study, the detection limit of gas-phase LIBS analysis has been improved by controlling the pressure and laser pulse width. In order to verify this method, low-pressure gas plasma was induced using nanosecond and picosecond lasers. The method was applied to the detection of Hg. The emission intensity ratio of the Hg atom to NO (IHg/ INO) was analyzed to evaluate the LIBS detection limit because the NO emission (interference signal) was formed during the plasma generation and cooling process of N2 and O2 in the air. It was demonstrated that the enhancement of IHg/INO arose by decreasing the pressure to a few kilopascals, and the IHg/INO of the picosecond breakdown was always much higher than that of the nanosecond breakdown at low buffer gas pressure. Enhancement of IHg/INO increased more than 10 times at 700 Pa using picosecond laser with 35 ps pulse width. The detection limit was enhanced to 0.03 ppm (parts per million). We also saw that the spectra from the center and edge parts of plasma showed different features. Comparing the central spectra with the edge spectra, IHg/INO of the edge spectra was higher than that of the central spectra using the picosecond laser breakdown process.