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HK: Physik der Hadronen und Kerne
HK 19: Kernphysik III / Magnetische Momente
HK 19.2: Vortrag
Dienstag, 23. März 1999, 14:30–14:45, B
Evidence of neutron configurations for excited states of 144,146Nd from magnetic moment measurements+ — •K.-H. Speidel1,2, N. Benzcer-Koller2, J. Holden2, G. Jakob2, G. Kumbartzki2, A. Macchiavelli3, M. McMahan3, W. Rogers4, A. Davis4, J. Mitchell4, P. Maier-Komor5, and A.E. Stuchbery6 — 1Institut für Strahlen- und Kernphysik, Univ. Bonn, D-53115 Bonn — 2Dept. of Physics & Astronomy, Rutgers Univ. NJ, USA — 3LBL Berkeley CA, USA — 4Westmond College CA, USA — 5Physik-Dept. TU-München, D-85748 Garching — 6Australian National Univ., Canberra Australia
The g-factors of the first 2+ states in 144−150Nd isotopes have been measured with the standard transient field (TF) technique by several groups (see e.g.[1]) and are in excellent agreement with each other. However, the data cannot be explained either with a simple collective Z/A description or with a more comprehensive IBA-II calculation. Both these models predict a decrease of g-factors with increasing neutron number. Obviously single neutrons outside the N=82 shell play an important role in the structure of these nuclei. Therefore further measurements with 144,146Nd beams of high energies were performed to determine the magnetic moments of the 4+ and 6+ states for the first time. Beams of Nd isotopes with an energy of ∼600 MeV were provided by the 88” cyclotron of LBL. The 2+, 4+ and 6+ states were Coulomb excited in inverse kinematics with a Ni target. The γ-rays were detected in coincidence with the forward recoiling Ni ions in 4 Ge detectors. For the precessions in the TF Gd was used as host. As a result the g-factors of the first 2+ states were determined to very high precision which agree very well with the known values. The g-factors of the 4+ and 6+ states are significantly smaller than those of the 2+ states. This result is a strong indication that f7/2 neutrons are a major component in the wavefunction. As neutrons are added the single particle effects decrease and the collectivity dominates in the heavier isotopes.
[1] A.E. Stuchbery et al., Nucl. Phys. A516(1990)119 +supported by the DFG