The long-lived noble-gas isotope ⁸¹Kr is the ideal tracer for old water and ice in the age range of 10⁵ – 10⁶ years, a range beyond the reach of ¹⁴C. ⁸¹Kr-dating, a concept pursued over the past four decades by numerous laboratories employing a variety of techniques, is now available for the first time to the earth science community at large. This is made possible by the development of an atom counter based on the Atom Trap Trace Analysis (ATTA) method, in which individual atoms of the desired isotope are selectively captured and detected with a laser-based atom trap. ATTA possesses superior selectivity, and is thus far used to analyze the environmental radioactive isotopes ⁸¹Kr, ⁸⁵Kr, and ³⁹Ar, These three isotopes have extremely low isotopic abundances in the range of 10^-16 to 10^-11, and cover a wide range of ages and applications. In collaboration with earth scientists, we are dating groundwater and mapping its flow in major aquifers around the world.

Argonne Physics Division Colloquium Schedule