原子番号効果

atomic-number effect

[目次：分光分析(EELS／EDS／電子構造)]

特性X線の分光分析(EDS)において、入射電子線が後方散乱されて、目的元素のX線放出(目的元素の電子励起)に寄与しない電子の割合が試料の平均原子番号に依存するために、試料から放出される特性X線が原子番号に依存する効果。試料を構成する複数の元素の原子番号が大きく違うときにこの効果が無視できなくなる。試料が厚くなると(測定元素により違いがあるが、ほぼ数10nm以上)、定量測定の際、この効果が無視できなくなるので、検出したX線の強度を補正する必要がある。

In spectroscopic analysis of characteristic X-rays (EDS), the "atomic-number effect" means that, since the amount of incident electrons which do not contribute to the emission of the characteristic X-rays of a target element (the excitation of the electrons of the target element) due to backscattering of the incident electrons is dependent on the average atomic number, the intensity of the X-rays generated from the specimen is dependent on the atomic numbers of the constituent elements of the specimen. When the atomic numbers of constituent elements are largely different, this effect has to be considered. Since this effect cannot be neglected in quantitative analysis when a specimen is thicker (～several 10 nm or thicker though depending on measured elements), correction for the detected X-ray intensity is required.

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