Abstract Online monitoring or in-situ isotopic analysis techniques in extreme environments are strategic tools in nuclear industry. A new optical method for performing isotopic analysis in solid samples at ambient pressure has been developed: Laser-Induced Breakdown self-Reversal Isotopic Spectrometry (LIBRIS). This method uses self-absorption of atomic or ionic resonance lines that are emitted from a non-uniform laser-induced plasma. It takes advantage of the fact that the spectral width of the absorption dip is much smaller than the spectral width of the emission line profile. Isotopic measurements were carried out on lithium samples by measuring the spectral position of the absorption dip that is shown to have a linear dependence on the 6Li isotopic abundance. Stand-off and real-time analysis can be performed without any sample preparation or pre-treatment. The effect of the laser wavelength, of the ambient gas and of the gate delay is investigated. Optimum conditions lead to a relative uncertainty of about 6% on the isotopic abundance measurement of 6Li. The influence of the spectral shifts due to Stark and Doppler effects on the performance of LIBRIS are discussed.

中文翻译：

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用于锂同位素分析的激光诱导击穿自反转同位素光谱法

摘要 极端环境下的在线监测或原位同位素分析技术是核工业的战略工具。已开发出一种在环境压力下对固体样品进行同位素分析的新光学方法：激光诱导击穿自反转同位素光谱法 (LIBRIS)。该方法使用从非均匀激光诱导等离子体发射的原子或离子共振线的自吸收。它利用了吸收倾角的光谱宽度远小于发射线轮廓的光谱宽度这一事实。通过测量吸收倾角的光谱位置对锂样品进行同位素测量，该吸收倾角与 6Li 同位素丰度呈线性相关。无需任何样品制备或预处理即可进行隔离和实时分析。研究了激光波长、环境气体和门延迟的影响。最佳条件导致 6Li 同位素丰度测量的相对不确定度约为 6%。讨论了由于斯塔克效应和多普勒效应引起的频谱偏移对 LIBRIS 性能的影响。