Fu Hongbo, Dong Fengzhong, Wang Huadong, Jia Junwei, Ni Zhibo
1 Anhui Provincial Key Laboratory of Photonic Devices and Materials, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei, China.
2 School of Environment Science and Optoelectronic Technology, University of Science and Technology of China, Hefei, China.
Appl Spectrosc. 2017 Aug;71(8):1982-1989. doi: 10.1177/0003702817699410. Epub 2017 May 9.
In this work, calibration-free laser-induced breakdown spectroscopy (CF-LIBS) is used to analyze a certified stainless steel sample. Due to self-absorption of the spectral lines from the major element Fe and the sparse lines of trace elements, it is usually not easy to construct the Boltzmann plots of all species. A standard reference line method is proposed here to solve this difficulty under the assumption of local thermodynamic equilibrium so that the same temperature value for all elements present into the plasma can be considered. Based on the concentration and rich spectral lines of Fe, the Stark broadening of Fe(I) 381.584 nm and Saha-Boltzmann plots of this element are used to calculate the electron density and the plasma temperature, respectively. In order to determine the plasma temperature accurately, which is seriously affected by self-absorption, a pre-selection procedure for eliminating those spectral lines with strong self-absorption is employed. Then, one spectral line of each element is selected to calculate its corresponding concentration. The results from the standard reference lines with and without self-absorption of Fe are compared. This method allows us to measure trace element content and effectively avoid the adverse effects due to self-absorption.
在这项工作中，采用无校准激光诱导击穿光谱法（CF-LIBS）对一个经过认证的不锈钢样品进行分析。由于主要元素Fe的光谱线存在自吸收以及痕量元素的谱线稀疏，通常很难构建所有元素的玻尔兹曼图。在此提出一种标准参考线方法，在局部热力学平衡假设下解决这一难题，从而可以认为等离子体中所有元素具有相同的温度值。基于Fe的浓度和丰富的谱线，分别利用Fe(I) 381.584 nm的斯塔克展宽和该元素的萨哈-玻尔兹曼图来计算电子密度和等离子体温度。为了准确测定受自吸收严重影响的等离子体温度，采用了一种预筛选程序来消除那些具有强自吸收的谱线。然后，选择每个元素的一条谱线来计算其相应的浓度。比较了有无Fe自吸收的标准参考线的结果。该方法使我们能够测量痕量元素含量，并有效避免自吸收带来的不利影响。
