Abstract
The development of deformation and shape coexistence in the vicinity of doubly magic , related to the weakening of the shell closure, was addressed in a low-energy Coulomb excitation experiment using a radioactive beam from the SPIRAL facility at GANIL. The and states in were excited on and targets at two different beam energies. values between all observed states and the spectroscopic quadrupole moment of the state were extracted from the differential Coulomb excitation cross sections, indicating a prolate shape of the nucleus and giving evidence of an onset of deformation already two protons and two neutrons away from doubly magic . New Hartree-Fock-Bogoliubov based configuration mixing calculations have been performed with the Gogny D1S interaction for and neighboring nuclei using two different approaches: the angular momentum projected generator coordinate method considering axial quadrupole deformations and a five-dimensional approach including the triaxial degree of freedom. The experimental values and new calculations are furthermore compared to shell-model calculations and to relativistic mean-field calculations. The new results give insight into the weakening of the shell closure and the development of deformation in this neutron-rich region of the nuclear chart.
- Received 3 March 2009
DOI:https://doi.org/10.1103/PhysRevC.80.014317
©2009 American Physical Society