Trapping and Probing Rare Isotopes

We trap and probe atoms of rare isotopes,
and explore related scientific problems in the realm of physics and beyond.

Age Ranges of Radioisotope TracersAtom Trap Trace Analysis reaching parts-per-quadrillion sensitivity

We have developed the Atom Trap Trace Analysis (ATTA) method to analyze 81Kr and 85Kr at and below the part-per-trillion (PPT) level, and 39Ar at and below the part-per-quadrillion (PPQ) level. These three long-lived noble-gas isotopes possess ideal geophysical and geochemical properties for radioisotope dating and are particularly significant for applications in the earth sciences. ATTA-3, the most recently developed instrument, is now available for routine sample analysis in our Laboratory for Radiokrypton Dating and is beeing utilized in various projects applying radiokrypton dating to earth sciences.

 

EDMTesting time-reversal symmetry in atoms and nuclei

We are searching for a permanent electric-dipole moment (EDM) of the Ra-225 (t1/2 = 15 d) atom. A positive finding would signify the violation of time-reversal symmetry (T). This experiment provides an outstanding opportunity to search for new physics beyond the Standard Model. We have succeeded in realizing laser trapping and cooling of radium atoms (both Ra-226 and Ra-225) for the first time ever. At present, we are developing the techniques and apparatus needed for the EDM measurements with cold Ra-225 atoms.

 

Studying exotic nuclear structure

Helium-8 (He-8) is the most neutron-rich matter that can be synthesized on earth: it consists of two protons and six neutrons, and remains stable for an average of 0.2 seconds. Because of its intriguing properties, He-8 has the potential to reveal new aspects of the fundamental forces among the constituent nucleons. We have succeeded in laser trapping and cooling this exotic helium isotope, produced at the GANIL cyclotron facility in northern France, and have performed precision laser spectroscopy on individual trapped atoms. Based on atomic frequency differences measured along the isotope chain He-3 – He-4 – He-6 – He-8, the nuclear charge radius of He-8 has been determined for the first time. The results, covered in a recent Colloquium in Reviews of Modern Physics, can now be compared with the values predicted by a number of nuclear structure calculations and is testing their ability to characterize this loosely-bound halo nucleus.

Helium

 

Other Research Projects

 

We acknowledge the support of DOE, Office of Nuclear Physics.