Improvements on Atom Trap Trace Analysis of ³⁹Ar

The noble gas radioisotope ³⁹Ar (half-life = 268 years) is a natural clock in the environment and nearly ideal for dating water and ice in the age range of 50-1800 years due to its gaseous and inert properties. This extremely rare isotope (isotopic abundances in the environment of 10^-17-10^-15) can be measured by the laser-based method Atom Trap Trace Analysis (ATTA), which features ultra-high selectivity and sensitivity. However, in the past the use of ³⁹Ar dating in applications such as dating of ocean water and ice cores was hampered by sample size requirement, precision and sample throughput of the ³⁹Ar analysis.

We report on the latest advances of ³⁹Ar analysis using ATTA, including increased ³⁹Ar detection efficiency and a reduced ³⁹Ar background, resulting in a two-fold increase in the upper age limit of ³⁹Ar dating. Moreover, we have developed a ³⁹Ar pre-enrichment system based on mass spectrometric techniques and obtain ³⁹Ar count rates up to 1000 atoms/h, two orders of magnitude higher than in previous efforts. This allows for a considerably higher sample throughput, which is particularly crucial for large scale surveys of global ocean circulations. Thanks to the progress in ³⁹Ar analysis, the full potential of radioargon dating over a wide timescale can now be exploited in groundwater, ocean water and glacier ice.

http://atta.ustc.edu.cn/en-us/events/attaprimer.html