We present a novel method for rapid and high-sensitivity in-situ measurements of the rare earth elements (REE) by combined secondary ion mass spectrometry and single-stage accelerator mass spectrometry (SIMS-SSAMS). Traditional SIMS can be limited in its REE sensitivity by the presence of abundant molecular isobars, whose discrimination is often beyond the range of high mass resolving power, and which require energy filtering and careful calibration to deconvolve. These greatly reduce sensitivity and require a priori assumption of terrestrial isotope ratios for deconvolution, which precludes the analysis of some nuclear forensic materials and presolar stardust grains. With the SSAMS, molecular background is reduced by 5 to 6 orders of magnitude, precluding the need for energy filtering and/or high mass resolution. We demonstrate measurement of Gd isotopes (6 µmol/mol) in the presence of a molecular background more than 4 orders of magnitude more intense from a single 15 µm spot in a sample of Madagascar hibonite. From the same spot we can resolve 7 nmol/mol of Tm from its comparably large background. Traditional SIMS requires the measurement of 47+ masses over 0.5 to 3 hours to perform REE deconvolution, while we collect full REE abundance patterns from several minerals in 10 to 30 minutes per spot. We observe no instrumental mass fractionation (±1%) in either Gd or Dy isotope ratio measurements of NIST610/612 glass. These improvements in sensitivity and measurement rapidity open important new avenues for REE imaging of samples and analyses of particles, nuclear materials, and mineral inclusions.

中文翻译：

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SIMS-SSAMS提供的快速，无分子的原位稀土元素丰度

我们提出了一种通过组合二次离子质谱和单级加速器质谱（SIMS-SSAMS）快速，高灵敏度就地测量稀土元素（REE）的新方法。传统的SIMS可能由于存在大量的分子等压线而限制了其REE敏感性，这些等压线的辨别力通常超出了高质量分辨能力的范围，并且需要进行能量过滤和仔细的校正才能消除卷积。这些大大降低了灵敏度，并且需要对地同位素比率进行反卷积的先验假设，这排除了对某些核法证材料和太阳前星尘颗粒进行分析的可能性。使用SSAMS，分子本底降低了5到6个数量级，从而消除了对能量过滤和/或高质量分离的需求。我们展示了在马达加斯加菱铁矿样品中单个15 µm斑点具有更强4个数量级的分子背景下，对Gd同位素（6 µmol / mol）的测量。从同一点，我们可以从相对较大的背景中分离出7 nmol / mol的Tm。传统的SIMS需要在0.5到3个小时内测量47个以上的质量才能进行REE反褶积，而我们需要在每点10到30分钟内收集几种矿物的完整REE丰度图。在NIST610 / 612玻璃的Gd或Dy同位素比测量中，我们没有观察到仪器质量分数（±1％）。灵敏度和测量速度的这些提高为样品的REE成像以及对颗粒，核材料和矿物包裹体的分析开辟了重要的新途径。