Level lifetimes and quadrupole moments from Coulomb excitation in the Ba chain and the N = 80 isotones
1 Institut für Kernphysik, Technische Universität Darmstadt, D-64289 Darmstadt, Germany
2 CERN, Genève, Switzerland
3 GSI Helmholtzzentrum für Schwerionenforschung mbH, D-64291 Darmstadt, Germany
4 Faculty of Physics, St. Kliment Ohridski University of Sofia, BG-1164 Sofia, Bulgaria
5 Argonne National Lab, Chicago, Illinois, U.S.A.
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The chain of Barium isotopes enables us to study experimentally the evolution of nuclear quadrupole collectivity from the shell closure at N = 82 towards neutron-deficient or neutron-rich deformed nuclei. The TU Darmstadt group has investigated several nuclei from stable 130,132Ba up to radioactive 140,142Ba with the projectile-Coulomb excitation technique including the use of the Doppler-shift attenuation method (DSAM). Lifetimes of quadrupole-collective states of 132Ba and 140Ba were obtained for the first time as well as the static electric quadrupole moments Q(21+) for 130,132Ba and 140,142Ba. The results are compared to Monte Carlo shell model and Beyond-Mean-Field calculations. The phenomenon of shell stabilization in the N = 80 isotones is further investigated by measurements of the B(E2;21+ → 01+) values of 140Nd and 142Sm and comparison to the quasi-particle phonon model and shell-model calculations.
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