M. Niikura, B. Mouginot, S. Franchoo, I. Matea, I. Stefan, D. Verney, F. Azaiez, M. Assie, P. Bednarczyk, C. Borcea, A. Burger, G. Burgunder, A. Buta, L. Càceres, 2 E. Clément, L. Coquard, G. de Angelis, G. de France, F. de Oliveira Santos, A. Dewald, A. Dijon, Z. Dombradi, E. Fiori, C. Fransen, G. Friessner, L. Gaudefroy, G. Georgiev, S. Grévy, M. Hackstein, M. N. Harakeh, F. Ibrahim, O. Kamalou, M. Kmiecik, R. Lozeva, A. Maj, C. Mihai, O. Möller, S. Myalski, F. Negoita, D. Pantelica, L. Perrot, Th. Pissulla, F. Rotaru, W. Rother, J. A. Scarpaci, C. Stodel, J. C. Thomas, P. Ujic
We report here the first direct lifetime measurement of the 2+1 state in 72,74Zn. The neutron-rich beam was produced by in-flight fragmentation of 76Ge at the Grand Acc\'el\'erateur National d'Ions Lourds and separated with the LISE spectrometer. The 2+1 state was excited by inelastic scattering and knock-out reaction on a CD2 target and its lifetime was measured by the recoil-distance Dopplershift method with the K\"oln plunger device combined with the EXOGAM detectors. The lifetimes of the 2+1 states in 72,74Zn were determined to be 17.9(18) and 27.0(24) ps, which correspond to reduced transition probabilities B(E2; 2+1 \rightarrow 0+) = 385(39) and 370(33) e2fm4, respectively. These values support the idea of a systematic maximum of collectivity at N = 42 for Zn, Ge and Se nuclei. In addition, the available systematics in the neighboring nuclei point towards a transition from a spherical oscillator at N = 40 to complete {\gamma}-softness at N = 42.
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http://arxiv.org/abs/1105.4072
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