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Physical Review C 85 (2012) 054321
First direct lifetime measurement of the 2+1 state in 72,74Zn: new evidence for shape transition between N = 40 and N = 42 close to Z = 28
M. Niikura1, B. Mouginot1, F. Azaiez1, S. Franchoo1, I. Matea1, I. Stefan1, D. Verney1, M. Assie1, 2, P. Bednarczyk, C. Borcea, A. Burger, G. Burgunder2, A. Buta3, L. Càceres2, E. Clément2, L. Coquard, G. De Angelis, G. De France2, F. de Oliveira Santos2, A. Dewald, A. Dijon2, Z. Dombradi, E. Fiori4, C. Fransen, G. Friessner, L. Gaudefroy5, G. Georgiev4, S. Grévy2, M. Hackstein, M. N. Harakeh, F. Ibrahim1, O. Kamalou2, M. Kmiecik, R. Lozeva4, 6, A. Maj, C. Mihai, O. Möller, S. Myalski, F. Negoita, D. Pantelica, L. Perrot1, Th. Pissulla, F. Rotaru, W. Rother, J. A. Scarpaci1, C. Stodel2, J. C. Thomas2, P. Ujic2

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 Accélérateur 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 Köln 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.
1 :  IPNO - Institut de Physique Nucléaire d'Orsay
2 :  GANIL - Grand Accélérateur National d'Ions Lourds
3 :  NIPNE - Horia Hulubei National Institute of Physics and Nuclear Engineering
4 :  CSNSM - Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse
5 :  DAM/DIF - DAM Île-de-France
6 :  IPHC - Institut Pluridisciplinaire Hubert Curien
Physique/Physique Nucléaire Expérimentale
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