Nuclear Seminar

Laser Trapping and Probing of Exotic Helium Isotopes

Zheng-Tian Lu
Argonne National Laboratory

Monday, November 19, 2007   4:00 p.m.   NSH 124
(Refreshments served prior to seminar in NSH 124)

We have succeeded in laser trapping and cooling of the exotic helium isotopes, both ⁶He (t ½ = 0.8 sec) and ⁸He (t ½ = 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.