Optimizing the analyte introduction for 14C laser ablation-AMS,Journal of Analytical Atomic Spectrometry

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Optimizing the analyte introduction for 14C laser ablation-AMS
Journal of Analytical Atomic Spectrometry ( IF 3.1 ) Pub Date : 2017-07-10 00:00:00 , DOI: 10.1039/c7ja00118e
Caroline Welte _{1,

2,

3,

4,

5} , Lukas Wacker _{1,

2,

3,

4} , Bodo Hattendorf _{2,

3,

4,

5,

6} , Marcus Christl _{1,

2,

3,

4} , Joachim Koch _{2,

3,

4,

5,

6} , Christiane Yeman _{1,

2,

3,

4} , Sebastian F. M. Breitenbach _{7,

8,

9,

10,

11} , Hans-Arno Synal _{1,

2,

3,

4} , Detlef Günther _{2,

3,

4,

5,

6}

Affiliation

Recently a novel approach enabling spatially resolved analyses of radiocarbon (¹⁴C) in carbonates has been introduced, combining laser ablation with accelerator mass spectrometry (LA-AMS). Here, we present a comprehensive study to find optimum working conditions for LA-AMS. The stepwise optimization and characterization process comprises (i) finding a suitable laser source for the ablation of carbonates with highest CaCO₃ to C_gas (i.e. CO₂ or CO) conversion rate, (ii) studying different capillaries with different gas flow resistance that interface the LA-cell with the ion source of the AMS system, and (iii) determining the exchange rate of the LA cell and the width of a stalagmite's growth stop under real measurement conditions. Three laser sources (Nd:YAG@266 nm; Nd:YAG@213 nm; ArF excimer@193 nm) were tested at different fluences (3 and 23 J cm⁻²) for their C_gas-conversion efficiencies. Highest C_gas-conversion efficiencies of (70 ± 4)% were found with an ArF excimer laser, independently of laser fluence. The characterization of the system using different capillaries showed that gas flow rates applied in LA-AMS are more than a factor of five higher than for regular ¹⁴C AMS gas measurements, which probably results in reduced ionization efficiencies of the LA-AMS setup. An exchange rate of 10 min⁻¹ is determined for the LA-cell design applied in this study by matching a ¹⁴C dataset derived by LA-AMS with modeled data (χ²-fit). Additionally, the model allowed to estimate the width of a growth stop in a stalagmite sample to be on the order of 0.25 mm.

中文翻译：

优化¹⁴ C激光烧蚀AMS的分析物引入

最近，结合激光烧蚀和加速器质谱（LA-AMS），引入了一种能够对碳酸盐中的放射性碳（¹⁴ C）进行空间分辨分析的新颖方法。在这里，我们提出一项全面的研究，以找到LA-AMS的最佳工作条件。逐步优化和表征过程包括：（i）寻找合适的激光源，用于烧蚀具有最高CaCO ₃到C_气（即CO _2）的碳酸盐。或（CO）转化率；（ii）研究具有不同气流阻力的不同毛细管，这些毛细管将LA细胞与AMS系统的离子源连接，并且（iii）确定LA细胞的交换速率和石笋的宽度在实际测量条件下停止增长。测试了三种激光源（Nd：YAG @ 266 nm； Nd：YAG @ 213 nm； ArF受激准分子@ 193 nm）在不同注量（3和23 J cm ^-2）下的C_气转化效率。与ArF受激准分子激光器无关，最高的C_气转换效率为（70±4）％。使用不同毛细管的系统表征表明，LA-AMS中使用的气体流速比常规的¹⁴高了五倍以上C AMS气体测量，可能会导致LA-AMS设置的电离效率降低。的10分钟的汇率^-1是用于通过匹配在该研究中应用的LA-电池设计确定¹⁴通过LA-AMS与建模的数据导出的数据集Ç（χ ² -fit）。另外，该模型允许将石笋样品中的生长停止层的宽度估计为约0.25mm。

更新日期：2017-08-30

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