Coulomb Excitation of n-rich nuclei along the N = 50 shell closure

Recently, we have been investigating characteristics of nuclear states around the neutron-rich mass A=80 region [1]. Using the Radioactive Ion Beams (RIBs) produced at HRIBF, we have successfully measured the B(E2) values for $^{78,80,82}$Ge , using Coulomb excitation in inverse kinematics. For the germanium isotopes, these data allow a study of the systematic trend between the subshell $N$= 40 and the $N$=50 shell. Using the same technique, we have measured the B(E2) value of various nuclei along the $N$=50 shell including the radioactive nucleus $^{84}$Se. This value together with our previously measured $^{82}$Ge, and the recent result on $^{80}$Zn from ISOLDE [2] are providing basic experimental information needed for a better understanding of the neutron-rich nuclei around $A\sim $80. We report the new results and compare with shell model calculations. [1] E. Padilla-Rodal \textit{et al}., Phys. Rev. Lett. \textbf{94} (2005) 122501. [2] J. Van de Walle \textit{et al.}, Phys. Rev. Lett. \textbf{99} (2007) 142501.