Heidelberg 2015 – wissenschaftliches Programm
A 35.5: Poster
Donnerstag, 26. März 2015, 17:00–19:00, C/Foyer
Dating with Atom Trap Trace Analysis of 39Ar — •Sven Ebser1, Florian Ritterbusch1,2, Zhongyi Feng1, Anke Heilmann1, Arne Kersting2, Werner Aeschbach-Hertig2, and Markus K. Oberthaler1 — 1Kirchhoff-Institute for Physics, Heidelberg, Germany — 2Institute of Environmental Physics, Heidelberg, Germany
Atom Trap Trace Analysis (ATTA) is an ultra-sensitive counting method for rare isotopes. It is based on the high selectivity of resonant photon scattering during laser cooling and trapping in order to distinguish the rare isotope from the abundant ones. The special strength of this method lies in small sample sizes required for dating with long-lived isotopes.
We have developed an ATTA-setup for the rare argon isotope 39Ar. As an inert noble gas and with a half-life of 269 years it is the perfect tracer for dating ice and water samples in the time range between 50 and 1000 years before present. In this range no other reliable tracer exists. The experimental challenge lies in the low atmospheric abundance of 39Ar (39Ar/Ar = 8.23×10−16) and in the required stable and reproducible performance of all components of the apparatus leading to a robust 39Ar detection efficiency. We achieved a stable atmospheric count rate of 3.58 ± 0.10 atoms/h with which we dated groundwater samples with 39Ar-ATTA for the first time.