用XRF分析稀土元素时同位素激发源的选择

Choice of excitation source for determination of rare earth elements with radioisotope excited X ray fluorescence

根据 X射线荧光产生和探测的机理 ,用一些基本的物理参数 (光电质量吸收系数、荧光产额、吸收边阶跃比、被分析的 X荧光线相对于同线系的强度比等 )分析计算了在用同位素激发 X射线荧光分析技术(XRF)中最常见的两种激发源和 2 3 8Pu源分析稀土元素含量时 ,在不同的测量系统和分析条件下 ,每个元素的相对激发探测效率以及它们的优缺点 ,从而确定了对不同的稀土元素 ,选择何种激发源、测量何种特征 X线系 (KX和 LX) ,可使整个系统分析效果最佳。并用 Ce、Nd、Sm、Tb、Tm、Ho、Er、Yb和 L u等 9种稀土元素进行了实验研究 。

The comparisons of two radioisotope source ( 241 Am and 238 Pu) which are the most available in the radiosotope excited X Ray Fluorescence (XRF) analysis technique and two characteristic X ray series ( KX and LX) analyzed for the determination of the rare earth(RE) elements were investigated in detail. According to the principle of emission and detectionof X ray ,the relative excitation efficiencies were calculated by the some fundamental physical parameters includeding the photoelectric mass attenuation coefficient, the fluorescent yield, the absorption jump factor, the emission probability of the detected fluorescent lime with reference to other lines of the same series etc.. The advantages and disadvantages of the two conditions are discussed. These results may determine the optimal excitation and detection conditions for different rare earth elements. The experimental results with nine rare earth elements ( Ce,Nd,Sm,Tb,Tm,Ho, Er, Yb and Lu) are in agreement with the results of theoretical calculations.