In-Beam γ-Ray Spectroscopy of the N=50 Isotones on the Neutron-Rich Side.

High-spin states of 84Se, produced as a fission fragment in the fusion-fission reaction 18O+208Pb and studied with the EUROBALL IV array, have been identified for the first time. Their interpretation gives new insights about the evolution of the N=50 shell gap at the vicinity of 78Ni. To characterize this evolution, it would be worth using a new device devoted to the high-spin studies of neutron-rich nuclei produced by asymetric fission modes. Such dedicated studies are reported in a second part. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]