Résumé du preprint Irfu-11-94

Irfu-11-94
First spectroscopy of 66Se and 65As: investigating shape coexistence beyond the N = Z line.
A. Obertelli et al (S. Boissinot, F. Flavigny, W. Korten, J. Ljungvall, B. Sulignano)
We report on the rst spectroscopy of 66Se and 65As from two-neutron removal at intermediate beam energies. The deduced excitation energies for the rst-excited states in 66Se and 65As are compared to mean- eld-based predictions within a collective Hamiltonian formalism using the Gogny D1S e ective interaction and to state-of-the-art shell-model calculations restricted to the pf5=2g9=2 valence space. The obtained Coulomb-energy di erences for the rst excited states in 66Se and 65As are discussed within the shell-model formalism to assess the shape-coexistence picture for both nuclei. Our results support a favored oblate ground-state deformation in 66Se and 65As. A shape transition for the ground state of even-odd As isotopes from oblate in 65As to prolate in 67;69;71As is suggested.