Multiphonon excitations in Zn-62

We studied excited states in Zn-62 up to an excitation energy of 5.5 MeV via the Ni-61(He-3, 2n gamma) reaction at the Cologne Tandem accelerator with the high-efficiency HORUS cube spectrometer. We identified several multi-phonon excitations, especially two fragments of the one-phonon mixed-symmetry state 2(1,MS)(+) based on effective M1 and E2 transition strengths. The quantities were obtained from gamma gamma angular correlation and Doppler-shift measurements. Shell-model calculations performed for Zn-62 give clear support for the fragmentation of the one-phonon mixed-symmetry 2(1,MS)(+) state. The assumption of Zn-62 being a vibrator-like nucleus is supported by calculations of excitation energies and E2 and M1 transition strengths within the U(5) limit of the neutron-proton Interacting Boson Model. (C) 2010 Elsevier B.V. All rights reserved