Laser Trapping and Probing of Exotic Helium Isotopes
Dr. Peter Müller (Argonne National Lab)

We have succeeded in laser trapping and cooling of the exotic helium isotopes 6He (t1/2 = 0.8 sec) and 8He (t1/2 = 0.1 sec), and have performed precision laser spectroscopy on individual trapped atoms. Based on the atomic isotope shifts measured along the isotope chain 3He - 4He - 6He - 8He, and on the precise theory of the atomic structure of helium, the nuclear charge radii of 6He and 8He are determined for the first time in a method independent of nuclear models. The results are compared with the values predicted by a number of nuclear structure calculations and test their ability to characterize these neutron rich, loosely bound halo nuclei. The 6He measurement was performed at ATLAS of Argonne, and the 8He measurement at GANIL, France.