Zheng-tian lu
Physics Division, Argonne National Laboratory The Department of Physics & Enrico Fermi Institute, The University of Chicago Email: lu@anl.gov        Homepage: http://www-mep.phy.anl.gov/atta/

Since radiocarbon dating was first demonstrated in 1949, the field of trace analyses of long-lived cosmogenic isotopes has seen steady growth in both analytical methods and applicable isotopes. The impact of such analyses has reached a wide range of scientific and technological areas. A new method, named Atom Trap Trace Analysis (ATTA), was developed by our group and used to analyze ⁸¹Kr (t_1/2 = 2.3´10⁵ years, isotopic abundance ~ 1´10^-12) in environmental samples. In this method, individual ⁸¹Kr atoms are selectively captured and detected with a laser-based atom trap. ⁸¹Kr is produced by cosmic rays in the upper atmosphere. It is the ideal tracer for dating ice and groundwater in the age range of 10⁴–10⁶ years. As the first real-world application of ATTA, we have determined the mean residence time of the old groundwater in the Nubian Aquifer located underneath the Sahara Desert. Moreover, this method of capturing and probing atoms of rare isotopes is also applied to experiments that study exotic nuclear structure and test fundamental symmetries.