First direct lifetime measurement of the 2(1)(+) state in Zn-72,Zn-74: New evidence for a shape transition between N=40 and N=42 close to Z=28
de Angelis, G.
de France, Gilles
Santos, F. de Oliveira
Harakeh, M. N.
Scarpaci, J. A.
Thomas, J. C.
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We report here the first direct lifetime measurement of the 2(1)(+) state in Zn-72,Zn-74. The neutron-rich beam was produced by in-flight fragmentation of Ge-76 at the Grand Accelerateur National dIons 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 Doppler-shift method with the Koln plunger device combined with the EXOGAM detectors. The lifetimes of the 2(1)(+) states in Zn-72,Zn-74 were determined to be 17.9(18) and 27.0(24) ps, which correspond to reduced transition probabilities B(E2; 2(1)(+)- GT 0(+)) = 385(39) and 370(33) e(2) fm(4), 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 toward a transition from a spherical oscillator at N = 40 to complete gamma-softness at N = 42.
Source:Physical Review C, 2012, 85, 5
- German BMBF [06 DA 9040 I-1], Polish Ministry of Science and Higher Education [NN202 309135, NN202 109936], Hungarian Scientific Research Fund (OTKA)