最优化算法与纯元素谱剥离相结合的能量色散X射线荧光谱解谱方法

Combination of optimization algorithm and pure-element spectral stripping for the unfolding method of energy dispersive X-ray fluorescence spectrometry

在进行能量色散X射线荧光光谱(EDXRF)解谱时,如果给定样品的元素构成,采用纯元素谱图剥离的方式会更加合理,但由于每个元素的谱线都不止一条,如果仅仅针对主线对齐做剥离,会导致结果的严重失真,同时剥离次序对解谱结果有较大影响。介绍了一种最优化算法与纯元素谱剥离相结合的EDXRF解谱方法,该方法以多个纯元素谱的强度大小和峰位漂移道数作为变量构建残差方程,并用最优化计算的方法去调整,直至残差达到极小。实验采用强度顺序剥离、能量顺序剥离和最优化算法拟合3种方法分别对谱线重叠较为严重的LaCe-Pr-Nd混合液样品的L系谱线进行了解析,结果表明最优化计算方法拟合的谱图与原始谱的残差(1 415.0)比另两种方法(166 094.0和3 192.7)大幅度缩小,拟合谱与原始谱更为吻合,并且方法在实现时对初值不敏感,解谱精度也不依赖于剥离次序。

During the unfolding of energy dispersive X-ray fluorescence spectrometry (EDXRF), the method of pure-element spectral stripping will be more reasonable if the composition of sample is given. However, if there are two or more spectral lines for each element, the serious distortion of determination results will be caused if the stripping is conducted by only aligning the main line. Moreover, the stripping sequence will also have great influence on the unfolding results. A kind of unfolding method for EDXRF by combining optimization algorithm and pure-element spectral stripping was introduced. The intensity of every pure-element spectrum and number of peak shift were selected as variables to establish the residual equation. Then the equation was adjusted using optimization algorithm until the residue was minimal. The L-series spectral lines of La-Ce-Pr-Nd solution mixture with serious spectral overlapping were unfolded by three methods, i.e., stripping in intensity sequence, stripping in energy sequence, and fitting by optimization algorithm. The results showed that the residual error (σ) between original spectrum and spectrum obtained by optimization algorithm (1 415.0) was much lower than other two methods (166 094.0 and 3 192.7). The fitted spectrum was more consistent with the original spectrum. Moreover, this method was insensitive to the initial parameters, and the precision was not depended on the stripping sequence.