Jeudi 26 août, à 14h00
Excited state moment measurements are progressing on several fronts. This paper will present selected highlights of recent work.
A campaign of g-factor measurements by the High Velocity Transient Field (HVTF) technique at NSCL on the neutron-rich argon isotopes has been analyzed and is being interpreted . The results challenge shell model calculations but show a parallel with the moments (and hence the nuclear structure) of their stable Ca isotones, throwing light on the puzzling discrepancy between the experimental and theoretical B(E2) values in the N=28 nucleus 46Ar . Looking to the future, we have recently fund that segmentation of the particle detector has the potential to increase the anisotropy of the particle- angular correlations in intermediate energy Coulomb excitation, and hence improve the sensitivity of the HVTF technique.
For excited state moments of re-accelerated beams and fission fragments we are pursuing a systematic calibration of free ion hyperfine fields (i.e. Recoil in Vacuum, or RIV ) for ions between Z 30 and Z 50, and for recoil velocities in the range 0.02 < v/c < 0.06 . The sensitivity to the g factor often occurs for times below about 5 ps, an advantage for studies of exotic nuclei near closed shells. At longer times the attenuation reaches a ’hard core’, independent of the g factor, but dependent on the atomic spin. We have recently found evidence of sensitivity in the ’hard core’ values to whether the ion has an odd or even number of electrons.
*Supported by the Australian Research Council Discovery Grant No. DP0773273.
1. M.C. East, A.E. Stuchbery, H.L. Crawford, P.F. Mantica, T. Baugher, J. Berryman, A. Gade, G. Grinyer, S. McDaniel, D. Miller, K. Minamisono, A. Ratkiewicz, K. Starosta, J. Stoker, P. Voss, D. Weisshaar, in preparation.
2. A. Gade et al., Phys. Rev. C 68, 014302 (2003).
3. See for example A.E. Stuchbery and N.J. Stone, Phys. Rev. C 76, 034307 (2007).