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Rb同位素分析在地质探索和环境监测中具有重要应用价值. 本文基于可调谐激光吸收光谱技术, 通过热分解的样品处理方式, 搭建了一套Rb同位素吸收光谱测量装置, 实现了Rb同位素比稳定测量. 并通过新型多微管阵列结构设计原子发生器, 增强了其原子束准直能力, 有效抑制了光谱的多普勒效应, 提高Rb同位素光谱分辨率. 装置选用钽金属制作6 mm口径的高温原子发生器, 内部堆叠1 mm口径微管阵列, 发生器经电阻加热最高可达3000 ℃. 实验通过高温(600 ℃)催化Rb 2CO 3样品释放气态Rb原子, 同步利用探测激光通过Rb原子进行测量, 获得高分辨率Rb原子吸收光谱, 结合谱线参数反演获得自然丰度Rb 2CO 3样品中Rb同位素比( 85Rb∶ 87Rb)为2.441±0.02, 探测误差为5.9%, 87Rb检测极限达1.76‰ (3 σ). 实验结果表明, 相较于传统的单管结构, 采用多微管阵列结构进行测量时, Rb原子谱线展宽降低了约450 MHz (半高全宽), 可有效区分Rb同位素的吸收光谱特征. 多微管阵列结构的原子化装置与可调谐吸收光谱技术结合, 在固体金属检测领域具有探测精度高、光谱分辨能力强的优势, 为同位素丰度测量分析提供了可能, 具有广阔的应用前景.Rubidium (Rb) isotope analysis has important applications in geological exploration and environmental detection. Based on tunable laser atom absorption spectroscopy technology combined with thermal decomposition of the sample, a Rb isotope absorption spectroscopy measurement device is built to detect the Rb isotope ratio stability. And the atomic generator is designed by a new micro-channel array structure, which enhances atomic beam collimation capability, effectively suppresses the doppler effect of the spectrum, and improves the resolution of Rb isotope absorption spectrum. The device adopts tantalum metal to make the atomic generator with a diameter of 6 mm, and the micro-channel array with a diameter of 1 mm is stacked inside the atomic generator which can be heated resistively to 3000 ℃. In this experiment, the Rb carbonate sample is catalyzed to release Rb atom beam at a high temperature of 600 ℃, while a probe laser is used to obtain high resolution Rb absorption spectrum. The Rb isotope ratio ( 85Rb∶ 87Rb) of natural abundance Rb carbonate samples is 2.441±0.02 by combining the inversion of the spectral line parameters, the detection error is 5.9%, and the detection limit of 87Rb is 1.76‰ (3 σ). The experimental results show that the multi-microchannel structure reduces the linewidth of Rb atoms by 450 MHz (half height full width) compared with the counterparts of the single-channel structure, which can effectively distinguish the absorption characteristics of Rb isotopes. The device has a high detection accuracy and a high spectral resolution, which provides a possibility for the metal isotope abundance analysis, and has a broad application prospect.
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