基于平面反射镜约束的激光诱导击穿光谱技术研究

Research on laser-induced breakdown spectroscopy based on planar mirrors

为改善激光诱导击穿光谱技术(laser-induced breakdown spectroscopy,LIBS)的光谱特性,搭建了平面反射镜约束下的LIBS检测系统,将平面反射镜放置于样品两侧,分别选取平面反射镜间距7 mm,9 mm,11 mm,13 mm开展实验,得到等离子体辐射强度随平面反射镜间距增加而减小。研究了不同平面反射镜间距对土壤样品中Fe,Al,Pb 3种元素等离子体特性的影响,实验结果显示:相比于无平面反射镜约束,在平面反射镜间距为7 mm时,样品中Fe I,Al I,Pb I等3种元素的信噪比分别提高了29.9%,39.4%,31.0%;计算得到等离子体温度提高了484.54 K,等离子体电子密度提高了2.41×10^(15)cm^(-3)。对有无平面反射镜约束下的Pb元素进行定量分析,得到检测限从86.9 mg/kg降低到51.2 mg/kg,相对标准偏差从7.8%降低到4.6%。可见,利用平面反射镜是改善激光光谱特性的一种简单有效的方法。

In order to improve the spectral characteristics of laser-induced breakdown spectroscopy(LIBS),a LIBS detection system under the constraint of planar mirrors was built.The planar mirrors were placed on both sides of the sample.Planar mirror spacing of 7 mm, 9 mm, 11 mm and 13 mm were selected to carry out the experiment.It was obtained that the plasma radiation intensity decreases with the increase of the plane mirror spacing.The effects of different plane mirror spacing on the plasma properties of Fe, Al and Pb elements in soil samples were studied.The experimental results show that: compared with no plane mirror constraint, when the plane mirror spacing is 7 mm, the signal-to-noise ratio of the three elements Fe I,Al I,and Pb I in the sample is increased by 29.9%,39.4%,and 31.0%,respectively.The plasma temperature was increased by 484.54 K,and the plasma electron density was increased by 2.41×10^(15)cm^(-3).The detection limit was reduced from 86.9 mg/kg to 51.2 mg/kg and the relative standard deviation(RSD) was reduced from 7.8% to 4.6%.It can be seen that the use of planar mirrors is a simple and effective way to improve the spectral characteristics of laser.