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.
We have demonstrated new laser trapping methods for the search of an atomic electric dipole moment (EDM) of radium-225 setting a new limit that rapidly improved on our first measurement by a factor of 36. Permanent EDMs in atoms and particles constitute a property forbidden by the fundamental symmetries of space and time. Physical effects that violate these symmetries and that lie beyond the Standard Model of physics as it is known to date are needed to explain the dominance of matter over antimatter in the Universe. These effects may also induce EDMs observable in laboratories. In particular, the EDM of radium-225 is predicted to be greatly enhanced by its unusual pear-shaped nucleus. In our measurements, the atoms are held by an optical trap formed at a focal point of an intense laser beam. The spin precession of these trapped atoms is then studied to look for any changes due to an external electric field. Both measurements have yielded a null result on EDM - with increasingly tighter limits. Future searches at higher sensitivity levels are being planned.
Atom 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 utilized in various projects applying radiokrypton dating to earth sciences.
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.
Other Research Projects
We acknowledge the support of DOE, Office of Nuclear Physics.