Probing particle-phonon-coupled states in the neutron-rich nucleus 65Cu by lifetime measurements with fast-timing techniques

The Cu-65 nucleuswas populated by the Ni-64(Li-7,alpha 2n)Cu-65 reaction and the lifetime of the 9/2(+) state at 2.5 MeV was measured by electronic fast-timing technique, providing the value tau = 37(3) ps. The reduced transition probability B(E3) = 8.82(165) W.u. is deduced and compared to theoretical predictions in the framework of a particle-vibration (weak) coupling model. The results indicate that the 9/2(+) state is a member of the 3(-)circle times pi p3/2 multiplet, built by coupling the octupole 3(-) phonon of Ni-64 to an unpaired proton in the p(3/2) level, confirming the robustness of core excitations in the medium mass nucleus Ni-64.